2009-4, named as Flemingia macrophylla cv. Reyan No. 34, was bred after 12 years of several successive individual selection and propagation of original Flemingia macrophylla (Willd.) Prain introduced from International Center for Tropical Agriculture (CIAT). Comparative trial research showed that 2009-4 had high-yield, rich resistance, stronger stability and uniformity. DM yield was 15 021.30 kg/hm2 during variety comparison experiment, 51.96% and 78.10% very significantly higher than that of the parent ‘CIAT17407’ and check variety Tephrosia candida. The flowering period was earlier, generally in the middle of August, 30 days earlier than the control and 8 days later than the parent. The plant survival rate was significantly higher than that of the control and parent. It had a developed root system and drought resistance, and had the characteristics of high and stable yield during dry season at rainfall 755 mm above regions. It also had high adaptability to strong acid soil with pH 4.0-5.0, and could improve low fertilizer soil and poor soil. 2009-4 is suitable for the cultivation of tropical and subtropical areas in China, especially for the large-scale promotion of South China.
A total of 29 Dendrobium germplasms were studied with tailed primer M13 microsatellite markers (TP-M13- SSR). Analysis was made to perform the genetic diversity and establish the germplasms molecular ID. The results showed that by using 14 selected SSR markers, 191 alleles were detected and the detection rate was 79.31%-100% per primer. The polymorphism information content was 0.3877-0.9484, 0.7956 on average. Shannon’s information index was 0.8702-3.1553 and the average value was 2.1606. The genetic similarity coefficient of the germplasms ranged from 0.3037 to 0.9005, and all germplasms could be divided into 6 groups at 0.7000. Based on transferability and Shannon’s information index of the primers, more and more loci were added to distinguish all the germplasms. Finally, DoeSSR5, DoeSSR87 and DoeSSR97 at least were screened. Loci that amplified by the markers were coded to establish the unique and identifiable molecular ID of the germplasms.
In order to evaluate and analyze the genetic diversity of the tea germplasm resources from different regions, 72 kinds of germplasm resources from Fujian, Guangdong and Taiwan were selected as the research objects, and 27 phenotypic characters were observed and analysed. The 72 tea germplasms were rich in hereditary variability. The average genetic diversity index (H′) was 1.30 while the index of stem thick of tea was the biggest (2.15), and among them the quantitative character (1.82) was higher than that of the qualitative character (0.94). The average coefficient of variation (CV) of quantitative character was 17.86% while the biggest was the hundred-bud weight (29.21%), followed by the index of germination density (23.46%). Besides, the correlation analysis found that the relationship between multiple quantitative traits was complex. The correlation of 22 pairs of characters reached extremely significant level (P˂0.01), and that for 8 pairs of characters reached significant level (P˂0.05). Cluster analysis showed that the 72 germplasm were divided into four groups when the genetic distance was 16, the main characters of each group were significantly different, and the various morphological characters and evolutionary types were different. Principal component analysis showed that the characteristic number of the first 10 principal components were greater than 1, which representing 76.04% information of 27 phenotypic characters. The top five germplasm were selected, which could be used in the new products development, tea breeding based on the comprehensive score of the principal components. This study would provide some references for the development and utilization of the germplasm resources of tea and the breeding of new cultivars.
Cassava is an important food crop in the world. The presence of high-level cyanogenic glucosides and HCN produced poses a major nutritive drawback and means a higher labor costs to remove these toxic substances. Cyanogensis is an important protective mechanism for plant to avoid grazing by animals. Alpha-hydroxy nitrile lyase (HNL) plays a key role in cyanogensis reaction. We found that there was a premature termination mutation in the coding sequence of HNL gene of cassava variety SC8, which would result in short length in protein encoded and could affect the function of the protein. These researches would give useful information about the role of the point mutation and provide new ideals for selecting cassava accessions with low-content hydrocyanic acid in molecular breeding. Firstly we surveyed the resequencing data of 251 cassava varieties from all around the world to characterize the same mutation site in HNL gene and found that there were sixty accessions belonging to cultivated cassava harboring the same mutation as SC8, indicting the premature mutation occurred during or after cassava domestication. We cloned and sequenced the orthologous genes of 12G132600 in SC9 by PCR and compared the corresponding sequence of TME3 from the genome assembly. The results further strengthened the evidence of this premature mutation in cassava varieties.
45 phenotypic traits of 86 water lily (Nymphaea L.) resources in Hainan were surveyed, and the diversity, correlation, clustering and principal component analysis were conducted. The phenotypic traits of the 86 water lilies varied greatly, and the diversity indexes of 13 quantitative traits ranged from 0.612 to 2.041, with the highest value of petal width (2.041) and the lowest one of sepal number (0.612). The diversity indexes of 32 quality traits ranged from 0.259 to 1.648, in which the highest value was the flower color (1.648), and the lowest value was the stigma color (0.259) and the middle axon color (0.259). The variation coefficient of the 13 quantitative traits ranged from 19.98% to 122.06%, among which the number of stamens (122.06%) and the total number of petals (109.87%) were the two most varied traits. Correlation analysis showed that significant positive correlations (P<0.01) existed between the length of leaf and width of leaf, and other 5 couples of characteristics. Clustering analysis of the 86 water lilies were divided into four groups: Brachyceras, Anecphya, Lotus and Nymphaea. Eight principal components were extracted by principal component analysis with characteristic values greater than 1.5, and the cumulative contribution rate was 60.838%. Among the 86 water lilies N. gigantea ‘Albert de Lestang’ ranked the highest value in comprehensive score, and N. ‘Pygmaea Alba’ got the lowest one.
The relative germination potential, relative germination rate, germination drought tolerance index, relative radicle length, relative seedling height and vigor index were used as the evaluation indexes to evaluate the drought tolerance of 228 accessions of Crotalaria pallida. According to the average membership function values of the six evaluation indexes, the drought tolerance of the resources was divided into five grades. Among them, one accession germplasm with drought tolerance grade I came from Yunnan, with an average membership function value 0.8, 13 accessions with drought tolerance grade II had an average membership function value less than 0.8, greater than or equal to 0.6, 105 accessions with drought tolerance grade III had an average membership function value less than 0.6, greater than or equal to 0.4, 105 accessions with drought tolerance grade IV had an average membership function value less than 0.4, greater than or equal to 0.2, four accessions with drought tolerance grade V had an average membership function value less than 0.2.
Pigeonpea (Cajanus cajan) is the sixth largest edible beans globally with extensive usages. The characteristics of pigeonpea germplasm resources are closely related to the stress resistance due to the rich genetic diversity. This paper summarized the research progresses on genetic diversity, physiological and biochemical indices and mechanisms of stress resistance of global pigeonpea studies order to provide references for the future researches on stress resistance and pigeonpea breeding. The industrialization prospects of pigeonpea are also proposed here.
SVP (short vegetative phase) is a type of flowering suppressor gene, which regulates the expression of flowering-related genes to affect the transition process of plants from the vegetative growth stage to the reproductive growth stage. According to the published pineapple genome information, two AcSVP genes named AcSVP1 and AcSVP2 were cloned in ‘Tainong 4’ pineapple. Analyses showed that AcSVP1 and AcSVP2 encoded 225 and 230 amino acids, respectively, and both contained MADS-box and K-box conserved domains. The proteins encoded belonged to the MADS-box gene family members. qRT-PCR analysis showed that the genes were expressed in different degrees in stem tip, stem base and leaf tissues, and after ethephon treatment the genes were mainly down-regulated to varying degrees compared with the control. Within 8 h of ethephon treatment, AcSVP1 was significantly down-regulated in the stem tips and leaves while in the stem-basal tissue which showed a trend of first down and then up-regulation, and the relative expression of AcSVP1 in the stem-basal tissues was slightly higher than that of its control after 8 h of ethephon treatment. Different from AcSVP1, AcSVP2 gene was significantly down-regulated in stem tip, stem base and leaf tissues within 8 h of ethephon treatment, and the relative expression level of AcSVP2 in the stem tip, stem base and leaf tissues was respectively about 8%, 44% and 33% of the control after 8 h of ethylene treatment. SVP was the most important type of flowering suppressor gene. And the down-regulated of AcSVP in response to ethephon stimulation indicated that AcSVP maybe play a key role in the flowering processes of pineapple in responses to ethephon signal.
In this study, the MeLHCB4 coding region of cassava chlorophyll a-binding b binding protein gene was cloned by the RT-PCR technique. The structure of the gene and the physical and chemical properties of the protein encoded by the gene were analyzed by bioinformatics, and the LHCB4 amino acid sequences of different species were compared and the evolutionary tree was constructed. The results showed that the CDs sequence of cassava MeLHCB4 was 858 BP, encoding 285 amino acids, the theoretical molecular weight of the protein was about 30.9 kDa, and the theoretical isoelectric point was 5.47. The protein was a stable hydrophilic protein, and it was predicted that the protein might be located in the nucleus and cytoplasm. The expression pattern of MeLHCB4 was detected by real-time fluorescence quantitative PCR. It was found that MeLHCB4 was mainly expressed in the leaves and stems of cassava, and was induced by hormones such as JA, SA and ACC, which was speculated to be involved in JA, SA, ACC signal pathway. After 12 hours of Xanthomonas axonopodis pv. manihotis infecting cassava leaves, the expression of MeLHCB4 increased significantly, indicating that MeLHCB4 was involved in the response process of cassava to pathogens.
Glucose dehydrogenase (GDH) and pyrroloquinoline quinone (PQQE) play an important role in the dissolution of inorganic phosphorus by phosphorus-soluble microorganisms. The phosphorus-soluble mechanism of the nitrogen-fixing bacteria Klebsiella variicola DX120E in sugarcane was investigated. The ORF of the phosphorous-soluble gene GDH and pqqE were cloned from the bacterium and analysised by bioinformatics. At the same time, the utilization ability of the bacteria to different phosphorus sources was studied. The ORF of GDH and pqqE was 2373 bp and 1143 bp, the coding amino acids were 790 and 380, respectively. Bioinformatics analysis showed that GDH was a stable protein, but pqqE was an unstable one. GDH was a membrane receptor protein related to cell signaling, with PQQ_membr_ DH, PQQ_mGDH functional domain and PQQ_DH_like superfamily protein structure. pqqE encoded proteins called intracellular proteins, structure containing PQQ_syn_pqqE functional domain and Radical SAM superfamily proteins. The utilization of different phosphorus sources and the qRT-PCR analysis of GDH and pqqE in different phosphorus sources showed that under different conditions, the ability of the bacteria to dissolve phosphorus was FePO4>AlPO4> Ca3(PO4)2 and the ability to dissolve FePO4 was significantly different from that of Ca3(PO4)2 and AlPO4(P<0.05). Under the condition of several phosphorus sources, the relative expression of GDH and pqqE increased, and the expression change trend of the genes was the same. The expression of GDH and pqqE in phosphorus source was significantly different from that in Ca3(PO4)2(P<0.05). This study would lay a foundation for further study on the interaction and phosphorus dissolution mechanism between endophytic nitrogen-fixing bacteria and sugarcane.
Tetrastichus brontispae is the pupal parasitic wasp of Brontispa longissima, an exotically invasive pest. The analysis of SSR, SNP and InDel sites in the transcriptome sequences of T. brontispae can provide data support for the development of new molecular markers and the in-depth study of its genetic diversity, population genetic structure and historical dynamics. Based on transcriptional data, MISA software and Varscan software were used to search the SSR, SNP and InDel sites of Unigenes. A total of 29 754 SSR sites were obtained in 11 802 Unigenes, with an average of 1 SSR per 1.72 kb, with an incidence of 39.96%. The length of the SSR fragments was 10-382 bp, with an average length of 23.91 bp. In the SSR segment, mononucleotide was dominant (60.82%), followed by dinucleotide (27.69%) and trinucleotide (10.79%). In all repeating motifs, the dominant repeating motif was A/T (59.32%), followed by AT/AT (15.28%). Among 6 895 Unigenes, 51 334 SNP sites were discovered, and each Unigene contained 7.45 SNP on average. There were 37 445 transition sites (72.94%) and 13 975 transversion points (27.22%). 15 644 InDel sites were also identified out of 6 040 Unigene, with an average of 2.59 InDel per Unigene.SSR, SNP and InDel sites are abundant in the transcriptome of T. brontispae, with a large number, high occurrence frequency, rich type and polymorphism potential.
Areca catechu L. is an important economic crop in Hainan, China, the leaf yellowing has become increasingly serious, which is a major obstacle to the sustainable and healthy development of the areca industry. According to field research, the symptoms of leaf yellowing mainly included specific yellowing from 1/4 of leaf margin and whole leaf yellowing. In this study, 440 differentially co-expressed genes were screened in the specific leaf yellowing group by transcriptome sequencing, which were mainly concentrated in secondary metabolic pathways, hormone signal transduction pathways and energy metabolism pathways. This study explored the molecular mechanism of specific etiolation of areca leaves under different stresses and provided theoretical basis for the comprehensive prevention and control of areca plam yellowing disease.
Sugarcane (Saccharam spp.), a C4 tropical grass mainly for sugar production, is commercially cultivated in over 100 countries. One of the main barriers to mechanical or manual harvesting of whole sugarcane stalk is the high percentage of impurities, mainly the debris of leaves and sheathes that results in increase of harvest time and cost. The most efficient solution for this issue is to develop sugarcane cultivars that are easy to defoliate in sugarcane breeding program. In order to investigate the genes responsible to sugarcane defoliation, BSR-Seq technology was employed in the current study to analyze pools of the leaves at +6 position of extremely hard-to-defoliate and easy-to-defoliate sugarcane plants derived from the cross of ‘ROC25’ × ‘Yunzhe 89-7’, together with the two parental lines with contrast defoliation phenotypes. A total of 60 Gb of clean reads were obtained and the Q30 values of the four samples were greater than 93% with GC content of 51%. Using R570 genome as reference, the alignment rate was greater than 41%. A total of 4085 differential expressed genes were detected in the 4 samples. The candidate regions were found to locate at 4 loci on chromosome 9, covering a total length of 1.40 Mb in which 86 genes were annotated. There were 15 non-synonymous mutations annotated between the parental lines, and two significant differentially expressed genes (Sh09_g020620, Sh09_g020080) were identified. The expression level of Sh09 g020080 in the easy-to-defoliate genotype was higher than that of the hard-to-defoliate genotype and consistent with the parents but that of Sh09_g020620 was opposite between the offspring pools and the parental lines, suggesting that only Sh09 g020080 may contributing to the phenotype of easy defoliation. Quantitation of Sh09 g020080 gene expression in leaves from position +1 to +7 from the extremely easy-to-defoliate representative accession 40-159 and the extremely hard-to-defoliate accession 5-94 confirmed the BSR-seq results of the two pools. In analysis of another genetic population derived from the cross of ‘B35-9’ × ‘CP08-1553’, Sh09 g020080 was also found to express in a higher level in the extremely easy-to-defoliate accession 16-226 than in the extremely hard-to-defoliate accession 16-224 in +4 to +6 leaves. Analysis of the deduced Sh09_g020080 protein revealed that this protein has four domains conserved in σ factor-like proteins that may function in in red, far red and blue light reactions and accumulation of chlorophyll. Overall, this study shed a new light into the endeavor of exploring essential genes for defoliation in sugarcane.
In this paper, the activity of sucrose-metabolizing enzymes and expression of relevant genes in two carbon sinks (latex and trunk bark) that are directly involved in rubber production, as well as latex physiological parameters and bark n on-structural carbohydrate (NSC), were investigated in two Hevea varieties (‘Reyan7-33-97’ and ‘PR107’) of different rubber productivity during their peak yielding season. Seasonal dynamic change in dry rubber yield was larger in ‘PR107’ than in ‘Reyan7-33-97’, but both varieties exhibited a peak at late Sept. Latex total solid content, inorganic phosphorus and sucrose were not significantly different between the two varieties, but dry rubber content was significantly higher in ‘Reyan7-33-97’ than in ‘PR107’. Soluble sugar accounted for more than 80% of the NSC in trunk bark, and the differences in NSC and its component sugars (starch, soluble sugar and reducing sugar) were not significant between the two varieties. In the latex, sucrose synthase (Sus) catalyzed the reaction towards sucrose synthesis, and the activity of alkaline/neutral invertase (NIN) and Sus was not significantly different between the two varieties. In trunk bark, ‘Reyan7-33-97’ showed significantly higher NIN activity than ‘PR107’, but not significant between the two varieties for the other sucrose-metabolizing enzymes. In the latex, HbSWEET10a was abundantly expressed, and out of the eight sucrose-metabolizing genes examined, it was the only displaying significant differences in expression between the two varieties, with a higher expression in ‘Reyan7-33-97’. In trunk bark, of the seven sucrose-metabolizing genes examined, the expressions of HbSus3 and HbCIN2 were significantly higher in ‘PR107’ than in ‘Reyan7-33-97’, but HbSUT5 expression was lower in ‘PR107’. These results obtained here laid a foundation for further exploring the molecular interaction between the regulation of sucrose metabolism and latex regeneration.
Calmodulin-binding transcription activators (CAMTAs) are important proteins with a conserved calmodulin- binding domain, which are widely involved in biological processes such as stress response, growth and development, and hormone signalling in plant. In this study, we identified eight HbCAMTAs screening the genome-wide of the rubber tree and analyzed physicochemical properties, gene structures, regulatory elements, gene expression patterns, and so on. The results showed that all HbCAMTAs were located in the nucleus, and predicted as hydrophilic proteins with molecular weight from 104.34 to 121.99 kD and isoelectric points between 5.32 and 7.83. The sequence homology analysis showed that HbCAMTAs could be divided into four subclades, and each one had similar gene structure, conserved domains. Furthermore, each HbCAMTA was potentially regulated by at least three miRNAs. Expression analysis indicated that the expression of HbCAMTAs differed significantly in different tissues, and the expression was continuously up-regulated in leaves with the development of leaves and reached the highest expression level at mature or palegreen. Except for HbCAMTA2, ethylene stimulation failed to significantly induce the expression of other CAMTA genes in rubber tree while low-temperature could significantly induce the up-regulated expression of HbCAMTAs. HbCAMTA1 was constitutively expressed in all samples, and also mostly expressed in latex, leaves, roots, bark, male and female flowers, and four different leaf developmental stages (Bronzite, Changecolor, Palegreen, and Mature), which suggesting its fundamental function in rubber tree. HbCAMTA3 was expressed at the highest level in the seeds and was significantly up-regulated by low temperature stress, indicating its important role in response to low temperature stress. HbCAMTA7 was undetectably express in all investigated samples including different tissues, leaf developments, and treatments. Finally, this study would provide important information for further revealing the function of HbCAMTAs in rubber tree.
The latex physiological characteristics of three introduced rubber clones, such as latex yield, dry rubber content, initial flow rate, sucrose content, phosphorus content, Mg2+ content, and thiol content, were measured and analyzed. The results showed that, compared to the control clone ‘Reyan 73397’ and ‘RRIM 600’, there were significant differences among the rubber clones. According to high dry rubber yield, good latex stability, fast rubber-discharging, and high sugar utilization rate, ‘Reshi 09-5’ showed high-yielding potential, but the content of sucrose and initial flow rate of ‘Reshi 09-5’ were lower than that of ‘Reyan 73397’, and there was no significant differences in dry rubber content, thiol content and phosphorus content between them. ‘Reshi 09-6’ had higher dry rubber content and plug index than ‘RRIM 600’, and there was no significant differences in initial flow rate and sucrose content between them. All of these showed that ‘Reshi 09-6’ had better potential in latex production, but a low metabolic intensity, so the production can be increased by stimulated tapping. Compared to ‘RRIM600’, ‘Reshi 09-7’ had lower dry rubber yield, initial flow rate, and higher dry rubber content, which showed high latex discharging barrier and low sugar utilization efficiency, so it need to be further tested whether the yield can be improved by stimulated tapping in ‘Reshi 09-7’.
Using genotype TF291 as the test material, the effects of low phosphorus treatment (5 μmol/L) on the growth, antioxidant and antioxidant enzymes of Stylosanthes were analyzed to explore the response mechanism of the antioxidant system of Stylosanthes under low phosphorus stress. Compared with the control p treatment (250 μmol/L), the low p treatment inhibited the growth of stylox, and the chlorophyll concentration, maximum photochemical efficiency, abovementium and root biomass were significantly reduced (P<0.05). With the increase of the treatment time of low phosphorus, the activity of CAT, POD, SOD, ASP, PAL and the content of flavonoids in leaves were significantly increased at 15 d (P<0.05). The activity of CAT, SOD, ASP, PPO and content of MDA and H2O2 in leaves were significantly increased at 30 d (P<0.05). The study would provide an important basis for further exploring the molecular response mechanism of the antioxidant system of Stylosanthes cylindrica under low phosphorus stress.
The influence of different application rates of nitrogen and potassium on nutrient absorption and distribution and yield of grafted bitter gourd was discussed to solve the problem of over-application of fertilizers in the production of bitter gourd in winter. The bitter gourd grafted seedlings were treated with a control (T1), N 260 kg/hm2, K2O 430 kg/hm2 (T2), N 416 kg/hm2, K2O 768 kg/hm2 (T3), N 416 kg/hm2, K2O 192 kg/hm2 (T4), N 104 kg/hm2, K2O 768 kg/hm2 (T5), N 104 kg/hm2, K2O 192 kg/hm2(T6). The dry matter accumulation of different organs and the accumulation of nitrogen, phosphorus and potassium nutrients were determined in each growth period. The dry matter accumulation of various organs of grafted bitter gourd in different treatment increased with the extension of the growth period. Under the same condition of potassium application in the seedling and initial stages, the dry matter accumulation of stems, leaves and fruits was positively related with the nitrogen supply level. In the fruit-bearing period, under the same nitrogen application conditions, the dry matter accumulation of stems, leaves, and fruits increased significantly with the increase of potassium supply. Among them, the dry matter accumulation of all organs in different growth periods was equal to T2 treatment, significantly higher than that of other treatments. The total dry matter accumulation and fruit dry matter distribution rate reached the maximum in the full fruit stage, which was 590.76 g/plant and 43% respectively. The accumulation of nitrogen, phosphorus, and potassium in various organs of grafted bitter gourd with different treatment showed an upward trend with the extension of growth period. Grafted bitter gourd had a higher demand for potassium, followed by nitrogen and phosphorus. The accumulation of potassium continued to be at a high level, and the accumulation reached the highest level of 20.9, 3.5, 27.3 g per plant in the mature stage, respectively, an average increase of 52.7%, 43.2%, and 38.5% compared with the other treatments. Compared with the other treatments, T2 treatment significantly enhanced the nutrient supply capacity of the leaves (source) to the fruit (sink), and the dry matter distribution rate of nitrogen, phosphorus, and potassium in the fruit was 59%, 48%, and 48% at the mature stage, which was significantly higher than that of other treatments. Different treatment had differences in the yield of grafted bitter gourd. The yield of grafted bitter gourd under the same potassium application was significantly positively correlated with the nitrogen supply. The weight and yield of grafted bitter gourd in T2 treatment increased significantly by 37.1% and 46.4% respectively compared with the other treatments. Comprehensive research on the growth of grafted balsam pear and the effective utilization of nitrogen, phosphorus and potassium nutrients, T2 treatment (N 260 kg/hm2, K2O 430 kg/hm2) had the most significant effect on increasing the yield of grafted balsam pear. Promote the application and realize the “addition and subtraction” of green agriculture.
The effects on the cassava fresh root yield (FRY), root character, storage root configuration (SRC) were studied to obtain the optimal mechanized planting mode and harvesting agronomic-machinery parameters for cassava. A field experiment with six stake layouts, i.e. horizontal-orthodromic-symmetrical (T1), horizontal-orthodromic-interlace (T2), horizontal-slant-symmetrical (T3), horizontal-slant-interlace (T4), inclined-reverse-symmetrical (T5), inclined- reverse-interlace (T6) was conducted. Variety ‘NZ199’, which was widely cultivated across the South China and appropriate for mechanization, was used as the test material, adopted wide-narrow row (1.0 m+0.6 m) planting model on the flat field. The inclined model was helpful to increasing FRY than horizontal. The FRY of T6 and T1 was higher than that of others, up to 41.92-50.11, 38.55-48.42 t/hm2, respectively. The average half width across row of T6 and T1 SRC was narrower than others, only 22.92-24.09 cm. When the harvesting half width across row per plant was 30.0 cm and the harvesting depth was 25.0 cm, the fresh storage root weight proportion and their fresh root weight of T6 and T1 were higher than that of others, up to 97.54%-98.87%, 38.12-40.87 t/hm2, respectively. Comprehensive analysis, T6 and T1 were recommended within the wide-narrow row mechanized model on flat field, meanwhile, the parameter of 120.0 cm harvesting width and 25.0 cm depth were suggested for the double rows harvesting machine among narrow rows, then 98% of the FRY could be harvested.
In order to select suitable types of leaf fertilizer, promote the growth and improve the quality of Dendrobium nobilis, the effects of three chemical leaf fertilizers and three organic leaf fertilizers on the growth and quality of D. nobilis were studied by spray treatment. All fertilizer treatments increased tiller number, leaf number, stem section number, stem diameter and the plant height of D. nobilis, fresh weight, dry weight, FW/DW ratio and chlorophyll content in different degrees, but also improved the polysaccharides and total alkaloid content, thus spraying the leaf fertilizer could promote the growth and quality of D. nobilis. Among the three chemical fertilizers, the performance of promoting the growth and improving the quality of Wosheng was better than that of potassium dihydrogen phosphate, followed by Bihu. Compared with the control group, the stem diameter, fresh weight, dry weight, SPAD value, polysaccharide and total alkaloid content of D. nobilis were significantly increased after spraying Wosheng, and the growth rate was 21.87%, 35.68%, 39.50%, 7.96%, 15.01% and 9.89%, respectively. Among the three organic fertilizers, the performance of promoting the growth and improving the quality of potassium fulvic acid was better than that of Duligao, followed by Haidaosu. Compared with the control group, potassium fulvic acid significantly increased the stem diameter, fresh weight and dry weight of D. nobilis by 20.68%, 28.39% and 34.50%, respectively. Therefore, Wosheng and potassium fulvic acid significantly improved the growth and quality of D. nobile and could be used as foliar fertilizer for D. nobile cultivating under forest in Hainan.
The areca and vanilla intercropping system was used to explore the regular pattern of nitrogen nutrients utilization. ‘Reyin No.3’ Vanilla and ‘Reyin No.1’ Areca which were cultivated in the potted simulation experiments and three planting modes including areca monocropping, vanilla monocropping and areca intercropping with vanilla were used to study the effects of pure nitrogen content of 112.5 kg/hm2, 225 kg/hm2, 300 kg/hm2 and no nitrogen fertilizer treatments on plant biomass, nitrogen absorption and utilization, total soil nitrogen content and nitrogen use efficiency. With the increase of nitrogen fertilizer application, the fresh and dry biomass of the plants in different nitrogen treatments under different planting modes were significantly different (P<0.05). The fresh and dry biomass of the plants under the intercropping mode were highest and increasing by 61.3%, 34.9%, 43.1% and 47.2%, 62.7%, 33.8% respectively compared to the control. The total nitrogen content of plants under the intercropping mode was 0.43-2.63 mg/g higher than that of plants under the monocropping. The intercropping mode could significantly increase the nitrogen uptake of the plants, and increased by 40.44 kg/hm2, 47.79 kg/hm2and 53.92 kg/hm2 respectively compared to the control. The intercropping mode also could significantly increase the plant biomass, total nitrogen content, nitrogen uptake, nitrogen absorption efficiency, nitrogen use efficiency and nitrogen utilization efficiency, but had no obvious effect on soil total nitrogen content.
Pitaya is an important economic crop in tropical regions, and its planting scale has been expanding in recent years. However, research on the absorption and response of pitaya to phosphorus is still extremely scarce. In this study, ‘RuanZhi’ pitaya in potted planting was used to explore the appropriate phosphorus supply concentration of pitaya seedlings by analyzing the changes in root morphology and nutrient uptake of pitaya seedlings under different phosphorus levels. The amount of phosphorus added in the experiment was 0 mg/kg, 25 mg/kg, 50 mg/kg, 100 mg/kg. 200 mg/kg. The aboveground biomass of the seedlings at the phosphorus supply level of 25 mg/kg and 50 mg/kg was 37.1 g/plant and 36.2 g/plant, which was significantly higher than that of other treatments. Phosphorus supply level did not affect the absorption of above-ground phosphorus and potassium, but when the phosphorus supply level was 50 mg/kg, the nitrogen absorption was significantly higher than that of the phosphorus supply level 0 mg/kg, 100 mg/kg, and 200 mg/kg processing. The total root length of the seedlings at the phosphorus supply level of 25 mg/kg and 50 mg/kg was 1068.8 cm and 1069.6 cm, which was significantly higher than that of the other treatments., The root surface area of the phosphorus supply level of 50 mg/kg was significantly higher than that of the treatments of 0 mg/kg and 200 mg/kg. The content of soil alkali-hydrolyzable nitrogen was significantly negatively correlated with total root length and root surface area, indicating that the phosphorus supply level indirectly affected the nitrogen absorption of pitaya seedings by affecting root growth. In summary, phosphorus supply level at 50 mg/kg could improve the root morphology of pitaya seedlings and promote the absorption of nitrogen by seedlings.
A two-year pot-sand-culture experiment was conducted to investigate the root activity, root morphology, fresh weight and diameter of potential storage root, storage root numbers, single storage root fresh weight, root biomass, leaves area, stem-leaves biomass and both root and top dry matter allocation rate as well as root-top ratio (R/T) under phosphorus application P0.04 (P2O5 0.04 g/kg) on two sweetpotato varieties ‘Yanshu 25’ and ‘Pushu 32’. Compared with P0 (P2O5 0 g/kg), the total roots number, total roots fresh weight, length, surface area, mean diameter, volum and tips as well as root activity and the fresh weight and diameter of potential storage root at the early growth stage (0-30 days after planting) were significantly increased under proper phosphorus application (P0.04). Further more, sweetpotato leaf area index, fresh leaf weight, fresh stem weight, above-part fresh weight and dry weight accumulation of root, above-part and whole plant as well as dry matter to root partition ratio and root-top ratio were also increased at significant level under proper phosphorus application (P0.04). However, excessive P0.08 (P2O5 0.08 g/kg) inhibited the distribution of dry matter in roots, resulting in the decrease of root-top ratio, which was not conducive to the formation of storage root. At closure stage (40 days after planting), compared with P0, appropriate amount of phosphorus P0.04 (P2O5 0.04 g/kg) significantly increased the number of single plant storage root number (the number of storage root with diameter more than 5 mm was increased) and single storage root fresh weight, thus increased the weight of single plant. If the amount of phosphorus continued to increase, the number storage root number and single storage root fresh weight decreased significantly. Appropriate phosphorus application is of great significance to sweetpotato storage root formation. It would be beneficial to the formation of adventitious root, the growth and development of stem and leaf, and the dry matter synthesis of stem and leaf, thus laying a good material foundation for the formation of storage root, it could promote the distribution of dry matter to the root, increase the ratio of root to top, and promote the harmonious growth of plant, beneficial to storage root formation and the increase of storage root number.
In this experiment, two cherry tomato varieties, ‘Hongfei 6’ (HF) of waterlogging tolerance type and ‘Qianxi’ (QX) of sensitive type, were used as the materials, with normal moisture as the control (CK). Six flooding depth, respectively ?10 cm, ?5 cm, ?2 cm, 0 cm, 2 cm, 5 cm (D10, D5, D2, W0, U2, U5) was used to determine the growth, physiological and biochemical indicators of cherry tomato seedlings under different treatment to explore the response of cherry tomato at seedling stage to different flooding depths. Flooding treatment could inhibit the growth of plant height, stem thickness, dry matter weight, root length, root diameter, root surface area and root volume compared with CK. With the increase of flooding depth, plant height, dry matter mass, root length, root diameter, root surface area and root volume were inhibited more obviously, and the effects of W0, U2 and U5 were significantly lower than that of CK, while there was no significant difference in plant height, stem diameter and mean root diameter between D10, D5 and CK. The content of malondialdehyde (MDA), soluble sugar and proline gradually increased with the increase of the flooding depth. The activity of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) also showed a tendency to gradually increase with the increase of flooding depth, and from 2 to 6 days, the effects of D2, W0, U2, and U5 were higher than that of CK. After 14 days of flooding, the activity of SOD and CAT of QX of W0, U2 and U5 were significantly lower than those of CK. Correlation analysis revealed that MDA, POD, CAT, soluble sugar and proline were significantly positively correlated. Therefore, flooding depth was also an important factor for flood damage. Higher flooding depth would lead to greater damage to cherry tomatoes. 5 cm below the cherry tomato planting surface was the flooding depth threshold.
Artocarpus heterophyllus is a tropical fruit, and so far there are few reports on its mutants. In this study, the leaves of A. heterophyllus were used as the experimental materials to explore the possible reasons for the albinism and regreening of the leaves. The contents of chlorophyll and chlorophyll precursors in leaf mutants and normal green leaves were determined by conventional methods. The activity of chlorophyllase was determined by Elisa kit. The ultrastructure of chloroplast was observed by a transmission electron microscope. Chlorophyll a content, chlorophyll b content, total chlorophyll content and carotenoid content produced by different leaf colors were significantly different. There was no significant difference in the content of chlorophyll synthesis precursors between the mutant and the normal green leaves. In the determination of chlorophyll enzyme activity of the leaves, although there was a significant difference in its activity, it had no significant effect on the difference in chlorophyll content. When observing the ultrastructure of chloroplasts in the leaves, it was found that the chloroplasts in the normal green leaves were intact and had a large number, and the internal structure of chloroplasts in the albino leaves and the regreening leaves was defective, because the chloroplast grana construction stage was blocked. Based on the determination of chlorophyll, chlorophyll precursor content and chlorophyll enzyme activity in the leaves, the ultrastructure of chloroplast in the leaves was observed, and the data were compared and analyzed. In this study, it was speculated that during the chlorophyll synthesis stage, the blocked synthesis of chlorophyll by pchlide and the poor chloroplast development led to the albinism and regreening of A. heterophyllus, which would provide a theoretical basis for further comprehensive study of A. heterophyllus mutants.
Previous studies found that the exogenous GA signal affected sugarcane tillering process. In order to understand the effect of GA signal on the content of endogenous hormones in leaves at different time of tillering stage of sugarcane, this experiment used the main sugarcane variety ‘Guitang 42’ with excellent comprehensive traits as the plant material, and different exogenous GA signal regulators were used to soak the seedcanes with water treatment as the control (CK). The endogenous hormones indole-3-acetic acid (IAA) and gibberellins (GA), ethylene (ETH), cytokinin (CTK), abscisic acid (ABA) and brassinosteroids (BR) content in +1 leaves (main seedling + tiller seedling) at the early, full and late tillering stages were analyzed and the correlations between them were statistically tested. The results showed that after soaking sugarcane seedcanes with exogenous GA3 (Gibberellic acid 3; GA biosynthesis promoter), the total contents of IAA, GA and CTK in the tiller leaves was increased at the tillering stage, and the ETH content at the early stage and the ABA content at late tillering stage were increased. Paclobutracol (Paclobutracol, PP333; GA biosynthesis inhibitor) treatment increased the endogenous GA and ABA contents before tillering, and the ETH content at the later tiller leaves, but reduced the CTK and BR contents. Further correlation analysis found that in the treatment with exogenous gibberellin signal enhancer, the endogenous hormones of sugarcane leaves IAA and GA, CTK and BR, CTK and GA showed a significant positive correlation while ABA showed a significant negative correlation with GA but a significant positive correlation with ETH. The exogenous GA signal affected the endogenous hormone system in the leaves of sugarcane at the tillering stage, and the growth-promoting hormones and the growth-inhibiting hormones reached a dynamic equilibrium state, which ultimately led to the difference in the tillering. It is concluded that sugarcane tillering is closely related to the contents of plant endogenous hormones. Exogenous hormones could be used to influence the contents of endogenous hormones, regulate the dynamic balance between hormones, and achieve the purpose of improving sugarcane tiller formation and its stem formation.
In December 2018, a stem rot disease was found on Broussonetia papyrifera in Danzhou City, Hainan Province. Basidiocarps related to the disease were collected. The pathogenic pathogen was isolated by the conventional tissue separation method, and the pathogenicity was determined. The phylogenetic tree was constructed by ITS-SSU-LSU multi-gene combination. It was identified as Ganoderma australe by morphology and molecular biology. The results of biological characteristics showed that the pathogen grew well in 25-32 ℃, the optimal temperature was 28 ℃, the optimal growth pH was 4-7, and the optimal growth pH was 6. It grew well on CA, PDA and PSA medium, the optimal medium was PDA medium; light had inhibitory effect on the growth of mycelia of the pathogen.
At present, the disadvantages of chemical pesticides are prominent and the development of environmental friendly biocontrol agent is needed. The screening of biocontrol strains with inhibition of rubber anthracnose can reserve resources for the development of new biocontrol agents. The endophyte bacteria of rubber trees were isolated and purified by tissue culture, and growth plate-confrontation was used to screen antagonistic strains. Strain Bac RZS3D4-1, Bac RZS3D4-2, Bac RZS3D4-3, Bac RZS3D4-4 were identified based on morphological, physiological, biochemical characteristics and the phylogenetic tree was constructed with 16S rRNA and gyrA gene sequence. The growth plate-confrontation was used to study the antimicrobial persistence, stability and broad spectrum of endophytic bacteria. The Oxford cup method was used to study the sensitivity of antagonistic endophytic bacteria to fungicides. Four strains of bacteria (Bac RZS3D4-1, Bac RZS3D4-2, Bac RZS3D4-3, Bac RZS3D4-4) were isolated from the healthy root tissues of rubber trees. Phylogenetic tree analysis showed that the four strains were closely related to Bacillus amyloliquefaciens, and the culture traits and physiological and biochemical characteristics were similar to those of B. amyloliquefaciens. The results showed the strains had strong antibacterial persistence and good antibacterial stability, strong antibacterial activity against Colletotrichum acutatum (DFMP1E and Mlzzp3) and Pestalotiopsis microspora (MF375898), and weak inhibitory effect on Fusarium solani (XJ160901). They were not sensitive to carbendazim, isocarb, chlorothalonil and difenoconazole, so it is expected to be developed as a biocontrol agent.
Secondary metabolites play an important role in plant defense against phytophagous pests, however, to the best of our knowledge, there is lack of studies about the relationship between secondary metabolites and insect resistance of cassava. In this study, the contents of total phenol, malondialdehyde (MDA) and tannin in leaves of different cassava cultivars before and after being damaged by Paracoccus marginatus were analyzed. The results showed that there was no significant difference in the contents of total phenols and MDA in the leaves of the susceptible cassava cultivars such as ‘BRA900’ ‘bread’ cassava, ‘SC205’ and ‘Swiss T7’ after 1 d, 4 d and 8 d infestation, while the tannin content was significantly decreased over time. However, the content of total phenol and tannin in the leaves of the resistant cassava cultivars like ‘Myanmar’ and ‘C1115’ increased significantly, while the content of MDA decreased significantly. In addition, the content of total phenols in the insect-resistant cassava cultivars was significantly lower than those in susceptible ones before damaged by P. marginatus, while it was significantly higher than that of the susceptible cultivars as being damaged over time. There was no significant difference in MDA content between the insect-resistant and insect-susceptible cassava cultivars before damaged, while it was significantly lower than those in the susceptible ones after damaged for 1 d, 4 d and 8 d. Furthermore, the tannin content of the insect-resistant cassava cultivars was significantly higher than those of the susceptible ones before and after damaged by P. marginatus. The correlation analysis showed that the cassava resistance to P. marginatus was positively correlated with total phenol and tannin content, and negatively correlated with MDA content. This study preliminarily elucidated the mechanism of cassava resistance to P. marginatus based on secondary metabolites such as total phenols, MDA and tannin.
In order to clarify the important role of salicylic acid and jasmonic acid signal pathways in pepper aphid resistance, the study was based on obtaining genetically stable resistant and susceptible pepper varieties, and systematically carried out the difference analysis of salicylic acid and jasmonic acid content and related gene expression in leaf tissue of the aphid-resistance and aphid-susceptible reference peppers cultivars before and after damaged by Myzus persicae. After damaged by M. persicae, the content of salicylic acid in the aphid-resistant pepper variety ZDC and the aphid-susceptible pepper variety DYJJ increased significantly, while the content of jasmonic acid increased significantly in ZDC. In DYJJ, it decreased significantly and then returned to the pre-damage level. The expression levels of salicylic acid signaling pathway related genes PR1, EDS5, PAD4 could be significantly induced after ZDC and DYJJ damaged by M. persicae, and the expression level of PR1 and EDS5 genes in ZDC was significantly higher in ZDC and DYJJ in the early stage of damage. After ZDC was damaged by green peach aphid, the expression level of the jasmonic acid signaling pathway genes LOX2 and AOC increased significantly, and then gradually decreased to the pre-damage level. The expression of the genes in DYJJ was significantly inhibited and also significantly lower than that in ZDC. The results of this study indicate that pepper-resistant varieties can simultaneously activate salicylic acid and jasmonic acid signal pathways to resist the damage of green peach aphid, while the aphid-susceptible pepper variety activates the salicylic acid pathway and significantly inhibits the jasmonic acid pathway, which is beneficial to the green peach aphid infestation. This study initially revealed the molecular mechanism of pepper’s aphid resistance from the above two defense signal pathways.
The infection structures of Colletotrichum gloeosporioides on rubber trees would be clarified through microscopic observation to provide scientific basis for the anthracnose prediction in rubber trees. After rubber trees leaves treated with decolorizing agent (0.15% trichloroacetic acid-ethanol solution∶chloroform, 5∶1) for 12 h and 1% Congo red staining agent for 3 h, the developmental process and infection structure of C. gloeosporioides infection were clearly observed. Under the inoculation condition of 28 ℃ and 100% humidity, the crest-time of conidial germination was within 2-6 h after inoculated in rubber tree leaves at the light green phase. More than 85% of conidia were germinated after 12 h inoculation. The crest-time of appressorium formation was within 8-12 h after inoculation. About 75% germ tubes generated appressoria and appressoria began forming infection pegs after 12 h inoculation. The crest-time of infection pegs formation was at 24 h inoculation, while several germ tubes formed at the other top of the germinal conidium. The appressorium germinated to produce secondary appressorium, which further infected surrounding cells and caused leaves sporadic lesions at 36 h inoculation. After 48 h inoculation, Germ tubes of abundant branched differentiated into hyphae, some of which produced secondary conidia on the top. A large number of typical anthracnose spots formed. The hyphae spread vertically and horizontally on the leaf surface and gradually formed a net-like distribution after 72 h inoculation. As the hyphae expanded, a series of pathological changes occurred in the leaf tissue. In this study, a method for staining C. gloeosporioides in rubber tree leaves with good staining effects, simplicity, and efficiency was established, which further clarified the infection structures of C. gloeosporioides.
Pre-harvest fruit abscission phenomenon is intensive in off-season longan in Hainan, China, which seriously restricts the development of the off-season longan. Pedicel detaching force or fruit removal force, reflecting the separation status of the abscission zone, has been adopted as a direct index reflecting the process of fruit abscission. However, there has been no report about its use in longan. The purpose of our study was to evaluate the use of pedicel detaching force to reflect fruit abscission in off-season longan and clarify its correlation with availability of carbohydrates, fruit respiration rate and activities of wall-degrading enzymes in the abscission zone. Small clusters of fruit were harvested and pedicel detaching force was measured using DS2-1000 gf or DS2-5000 gf force gauges every day. At the same time, correlation of various physiological parameters with pedicel detaching force was analyzed. The pedicel detaching force of the off-season longan of ‘Chuliang’ ranged between 0 and 3000 gf. When it became less than 1000 gf, the fruit was doomed to abscise. The cumulative abscission rate was significantly and negatively correlated to pedicel detaching force, with a coefficient of -0.948 (P=0.000). Total sugar and starch content in fruit was significantly and positive correlated to pedicel detaching force with a correlation coefficient of 0.942 (P=0.005) and 0.952 (P=0.003), respectively. A moderate positive bud insignificant correlation was found between respiratory oxygen consumption and pedicel detaching force (r=-0.807, P=0.099). Activity of cellulase and β-mannanase in the abscission zone was negatively correlated to pedicel detaching force, with a correlation coefficient of ?0.936 (P=0.019) and -0.954 (P=0.002), respectively. The results showed changes in pedicel detaching force could be used to reflect the process of fruit abscission. Fruit abscission was accompanied by significant decrease in pedicel detaching force, which was highly correlated with carbohydrate availability and cell wall degrading enzyme activity in the abscission zone, and high fruit respiration consumption may accelerate the process of fruit abscission.
In order to understand the banana variety resources in Guangxi, banana varieties ‘Guijiao No. 6’, ‘Zhongjiao No. 3’, ‘Zhongjiao No. 4’, ‘Zhongjiao No. 6’, ‘Brazilian’ and ‘Nantianhuang’ were used as the test materials to compare the change rules of the quality during fruit ripening. In the process of post-ripening, the value a* of color difference, soluble solid, reducing sugar and total amylase activity for the six banana varieties showed a gradually increasing trend, the value L* of color difference, titratable acid and alpha-amylase activity increased firstly and then decreased. The starch content showed a gradually decreasing trend, and the value b* and C* of color difference fluctuated. The soluble sugar and vitamin C of ‘Brazilian’, 'Nantianhuang’ and ‘Zhongjiao No. 6’ were increased gradually and then stably, but the soluble sugar and vitamin C of ‘Zhongjiao No. 3’ and ‘Zhongjiao No. 4’ and the soluble protein of ‘Brazilian’ were gradually increased to yellow ripeness stage and then decreased. The soluble protein of ‘Guijiao No. 6’, ‘Zhongjiao No. 3’, ‘Zhongjiao No. 4’, ‘Zhongjiao No. 6’ and ‘Nantianhuang’ were gradually increased. In the yellow ripening stage, the peel thickness and finger curvature of ‘Zhongjiao No. 4’ were the biggest. The edible rate, finger length, value a* and reducing sugar content of ‘Guijiao No. 6’ were the largest. The single fruit weight, peel weight, titratable acid, soluble solids, and soluble sugar content of ‘Brazilian’ were the highest. Principal component analysis of the quality of the six banana varieties during the ripening period revealed the quality of ‘Guijiao No. 6’ was the best, followed by that of ‘Brazilian’, ‘Nantianhuang’, ‘Zhongjiao No. 3’, ‘Zhongjiao No. 6’, and ‘Zhongjiao No. 4’.
In order to select peanut varieties suitable for fresh eating and establish a quality evaluation method, 14 peanut varieties were introduced and planted in Hainan, the content of the soluble sugar, protein, fat, oleic acid and linoleic acid, and conduct sensory evaluation were detected by comparison with ‘Dongfang’ (CK), and the quality of different peanut varieties were comprehensively evaluated by correlation analysis and principal component analysis. Correlation analysis showed that the fresh weight of 100-pod was significantly positively correlated with the fresh weight of 100-kernel, the fresh weight of 100-pod was significantly negatively correlated with the content of linoleic acid, and the content of fat was extremely significant negative correlated with sweetness as well as the content of oleic acid and linoleic acid, and the aroma was positively correlated with sweetness and fineness. We got four principal component factors namely sensory factor, unsaturated fatty acid factor, protein factor, and yield factor, and the cumulative variance contribution rate was 80.601%. According to the comprehensive principal component scores, the fresh eating quality ranking of the tested peanut were ‘Silihong’ ‘Dongfang’ ‘Guihuahei 1’ ‘Guihuahong 132’ ‘Zhonghua 12’ ‘Zhonghua 16’ ‘Guihua 36’ ‘Guihua 56’ ‘Guihuahong 198’ ‘Guihua 771’ ‘Zhonghua 21’ ‘Zhonghua 26’ ‘Zhonghua 9’ ‘Zhonghua 24’ and ‘Zhonghua 6’. Comprehensive evaluation showed that ‘Silihong’ was more suitable for the Hainan environment and recommended as fresh eating peanut, followed by ‘Guihuahei 1’ and ‘Guihuahong 132’.
The borax/PVPP/phenol (BPP) protocol is a widespread protein extraction method in plant proteome research. However, BPP extraction of plant protein, combined with different precipitation agents, the precipitation time, yield and purity of extracted protein is strikingly different. In this study, Sesuvium portulacastrum and Para-rubber tree leaves, and rubber latex were used as the research materials. The plant protein was extracted and analyzed with precipitating agents of supersaturated potassium ammonium sulfate alcohol solution, ammonium acetate methanol solution and acetone solution. Using the methods of SDS-PAGE, gel electrophoresis image quality, mass spectrum identification, settling duration and comparative analysis of protein yield, it was showed that the protein bands extracted by the ammonium acetate precipitation method were not evident. Hevea leaves and latex showed a higher yield of protein in acetone solution. S. portulacastrum leaves had a higher yield of protein in supersaturated potassium ammonium sulfate alcohol solution. The clear background of gel electrophoresis figures was found for the supersaturated potassium ammonium sulfate ethanol solution and acetone solution. The comprehensive protein sequence information identified by mass spectrometry had a higher quality of precipitated protein. The research results can optimize the method of extracting high-quality plant protein, and it will be expected to provide references for recalcitrant plant taxa proteomics research in the future.
In this paper, the effects of heat combined citronella essential oil treatment on the preservation and activity of softening related enzymes were studied by using ‘Meizhonghong’ papaya as the test materials, and the fruit weight loss rate, hardness, color, titratable acid (TA), vitamin C (Vc), galacturonic acid polymer (PG), cellulase enzyme (CL), β-galactose glucoside enzyme (β-GAL) and methyl pectin enzyme (PE) activities were determined in the process of storage. Heat combined citronella essential oil treatment could improve the preserving quality by significantly reducing the disease index of papaya fruit, weight loss rate, decrease of firmness and yellow rate, and increasing the content of TSS and VC and TSS/TA ratio, slowing down the respiration rate and delaying the occurrence of respiration peak, meanwhile the activity of PG, PE and β-GAL enzymes, involved in the degradation of cell wall were significantly reduced by the combined treatment except the activity of CL enzyme which was not significantly influenced. In conclusion, heat combined citronella essential oil treatment showed good preservation effect on papaya fruit, delaying the decrease of fruit firmness, reducing the respiration rate and the activity of PG enzyme, PE enzyme and β-GAL enzyme.
The supplementary investigation and statistical analysis of pteridophytes in Jiulianshan Nature Reserve were conducted. There were 265 species of pteridophytes (including subspecies grade) belonging to 93 Genera and 43 families. The species composition was rich, and the richness index was the 2nd among the 8 forest ecotype nature reserves in Jiangxi Province. The dominant families and genera of pteridophytes were obvious. Dominant families consisted of Dryopteridaceae, Polypodiaceae, Athyriaceae, Thelypteridaceae. Dominant genera consisted of Dryopteris, Pteris, Selaginella, Asplenium. The flora of families and genera was dominated by the tropical elements, accounting for 55.81% and 69.89% of the total families and genera, respectively. The geographical composition of the species was dominated by the East Asian elements (47.9%), followed by the tropical elements (34.9%). The R/T value showed that the flora of pteridophytes to Jiulianshan was located in the transitional zone between the south subtropical zone and the middle subtropical zone. Cluster analysis showed that it was most closely related to Matoushan Nature Reserve and Qiyunshan Nature Reserve, and it belonged to east China in the pteridophytes geographical division
In order to explore the effect of Streptomyces 30702 and chitosan on the soil microbial activity and microbiome in Dioscorea oppositifolia L., the soil enzyme activity development was measured by colorimetric and titration methods, the change of the bacteria and fungi in soil microbiome was detected using the high-throughput sequencing technology and softwares such as Trimmomatic. The results showed that Streptomyces, chitosan, soil original microorganisms and culture time all affected the activity of urease and catalase in the soil significantly. The soil enzyme activity increased as chitosan concentration rose from 0 to 10.0 g/kg. As growing time went on, the soil enzyme activity increased first and then decreased obviously. Chitosan and Streptomyces interacted obviously. Streptomyces and chitosan increased the species abundance of soil bacteria and reduced the diversity of bacteria, increased the relative abundance of beneficial bacteria such as Ideonella and Cellvibrio, but had little effect on the species abundance and diversity of fungi and there was no significant difference between them and CK, the dominant bacteria genera in the soil were Humicola, Cladosporium, Sphingomonas and uncultured_bacterium_c_subgroup_6. Among them, the species abundance of bacteria in the Streptomyces 30702 2.5 g/kg treatment combined with chitosan was the largest, and the diversity of bacteria in the treatment was the least.
To evaluate the effects of co-application of biochar and nitrification inhibitor on regulating soil nitrification and mitigating N2O emission, an incubation experiment was conducted to explore the dynamic variations of inorganic N concentration and the associated intensity and N2O emissions in tropical vegetable soil. Four treatments were established as N fertilizer alone (N), N fertilizer applied with biochar (N+Bc), N fertilizer applied with nitrification inhibitor (N+Ni), and N fertilizer applied with biochar and nitrification inhibitor (N+Bc+Ni). Results showed that biochar amendment accelerated the conversion of NH4+-N to NO3--N, while nitrification inhibitor significantly decreased this process, and the co-application of the both weakened the nitrification to some extent. Moreover, biochar amendment elevated the NO3--N intensity by 15.8%, while nitrification inhibitor amendment promoted NH4+-N intensity by 33.4%, and the significant interaction occurred between biochar and nitrification inhibitor on NH4+-N and NO3--N intensity. In addition, NO2--N intensity was decreased by biochar or nitrification inhibitor amendment, with the latter having more obvious effects. Furthermore, biochar and nitrification inhibitor amendment alone decreased N2O emission by 15.1%-68.3%, and further decline in N2O emission occurred in the co-application of the both. Therefore, the co-application of biochar and nitrification inhibitor would be a promising strategy for simultaneously sequencing carbon and mitigating N2O emission in tropical vegetable soil.
