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  • Plant Protection & Bio-safety
    YU Haiying, LAN Jianqiang, LIU Lin
    Chinese Journal of Tropical Crops. 2022, 43(2): 361-368. https://doi.org/10.3969/j.issn.1000-2561.2022.02.017

    Colletotrichum sp. is a kind of fungus with wide geographical distribution and wide host range. It can infect plants and fruits before and after ripening, especially for mature tropical crops, causing serious economic losses and affecting the export quality of products. The infection process of C. gloeosporioides on mango fruit and the interaction between C. gloeosporioides and mango host were studied to reveal the infection mode and expansion pathway of the pathogen on fruit and leaves. After Inoculating the healthy ‘Sannian mango’ fruits and leaves with the strong pathogenic strain CG16 isolated and screened from the diseased fruit of local variety ‘Sannian mango’ in Yuanjiang, the histopathology and ultrastructure of mango fruits and leaves infected by C. gloeosporioides were studied by light microscope, scanning electron microscope and transmission electron microscopy. C. gloeosporioides formed primary hyphae 12 hours after infection, and the primary hyphae penetrating the host cell wall formed a funnel-shaped hyphal cone. It constricted at the hyphae in contact with the host cell wall, often formed a diaphragm, and expanded rapidly into normal hyphae after passing through the host cell wall. It took about one day from the inoculation of mango to the appearance of symptoms. In the process of infecting mango, C. gloeosporioides first formed the primary infection hyphae, and the host cells gradually disappeared and died with the invasion and expansion of the primary hyphae. The primary hyphae first spread between cells and continuously established new nutritional parasitic relationships in vivo. 2.5 days after inoculation, with the invasion of hyphae, the host cells finally died and dissolved, and the expanded hyphae diffused in the dead host cells gradually became thinner and more branched, and the secondary hyphae was formed. The secondary hyphae propagated and expanded in large numbers dispersing or forming mycelial bundles in the host. Four days after inoculation, a series of pathological changes occurred in host tissues and cells, including deformation of host cells, thinning of cell walls, deformity and partial disappearance of cells, disintegration of protoplasts and other organelles, necrosis and cell death. Five days after inoculation, the secondary hyphae in the vegetative stage of dead body proliferated and expanded in the dead host cells. Six days after inoculation, the conidiophores formed, and the spores began to mature and fall off 8 days after inoculation. In this study, the way of infection and expansion of C. gloeosporioides in fruits and leaves, as well as a series of pathological changes in host tissues in the process of infection were revealed, which would provide a theoretical basis for the prevention and control of the disease in production.

  • Special Topic of Natural Rubber
    ZHANG Hongtao, XIAO Xiaohu, YANG Jianghua, QIN Yunxia, LONG Xiangyu, YIN Hongyan, FANG Yongjun
    Chinese Journal of Tropical Crops. 2022, 43(11): 2188-2198. https://doi.org/10.3969/j.issn.1000-2561.2022.11.002

    YABBY genes family is a plant-specific transcription factor, which plays an important role in the development of plant leaves, floral organs and abiotic stress response, but it has not been reported in rubber tree so far. In this study, eleven HbYABBY genes were identified from the genome of Hevea brasiliensis, and the gene structure, promoter regulatory elements, chromosome location and collinearity, phylogeny and gene expression were analyzed. The results showed that the HbYABBY family genes were distributed on nine chromosomes. The length of the encoded protein was between 141 and 233 amino acids, and the molecular weight was ranged from 14.75 to 26.41kDa. The promoter regions contained response elements such as stress response, among which the number of light response elements was the largest. Gene transcriptional analysis showed that HbYABBY had significant tissue-specific expression profile, eight genes were only highly expressed in leaves and flowers but not in latex and roots. During the leaf development, except for HbCRC1, the expression of the other 9 HbYABBY were significantly down-regulated, which indicated that HbYABBY were deeply involved in the regulation of leaf development of rubber trees. Furthermore, both transcriptional and RT-qPCR experiments showed that HbYABBY genes were continuously down-regulated under high temperature treatment, indicating the regulatory roles in high temperature stress responses of rubber trees. In this paper, YABBY genes were firstly reported in H. brasiliensis, the physical and chemical characteristics, expressions and function of the genes were preliminarily studied, which would provide a solid foundation to investigate the functions and evolution of HbYABBY genes.