Abstract:

Sporangium is an important basis for the Phytophthora foot rot disease control and the pathogen (Phytophthora capsici) research in black pepper, but the sporangium-inducing methods and the micro development processes have not been reported yet. Three sporangium-inducing methods were tested and the sporangia development processes were observed by light microscope and laser confocal microscope. Abundant sporangia could be detected by all the three methods. The most sporangia were obtained by the method of lighting and glass rod-plastering induction on V8-A plates, followed by the lighting induction on V8-A plates and lighting induction in V8 liquid. Under light microscope, sporangia initially formed at the top of the hypha with the shape of small sphere, and gradually formed into an inverted pear shape. When matured, the sporangia released a large number of zoospores from an apical pore. Interestingly, a few sporangia germinated directly and formed a germ tube. Under laser confocal microscope, the protoplast of a sporangium was separated into dozens of small cells by membrane structure at first, and then multiple nuclear DNA was accumulated in each cell, and finally the multinuclear cell developed into several mononuclear zoospores. The study revealed the morphological characteristics of the P. capsici sporangium development progress would provide sporangium-inducing methods for further pathogenic mechanisms research and field disease management.

Key words: black pepper phytophthora foot rot, Phytophthora capsici, sporangia induction, development process