Soil mycoflora in the rhizozphere of black pepper (Piper nigrum L.) and their antagonisms against Phytophthora capsici Leon.

Studies were conducted to isolate, identify and determine the soil mycoflora from the rhizosphere of black pepper on various cropping patterns in Batangas and Laguna [Philippines]. The antagonistic activities of the isolates against Phytophthora capsici, a pathogen causing stem rot or root rot of black pepper (Piper nigrum L.) were determined. One hundred and forty nine colonies of soil mycoflora were isolated and 14 genera from these isolates were identified. The genera Penicillium, Paecilomyces and Aspergillus have the most number of isolates among all the genera. Screening of those isolates was done in the laboratory using the dual culture technique. Eighteen promising antagonist isolates were found from among the 149 isolates, whose percentage of inhibition of radial growth (PIRG) of P. capsici were more than 60%. The ability of Mucor (Isolate no. 101), Trichoderma (125, 170, 171, 179, 180, 181), Gliocladium (109), Cunninghamella (165, 168), Mortierella (177) and Aspergillus (106) to grow rapidly is a probable mechanism by which those fungi were able to control the growth of the pathogen in vitro. Aspergillus (67, 79, 81, 83, 108, 202) apparently produced some substances that inhibited the growth of the pathogen, thus the presence of a clear zone between them. Aspergillus (83) also caused abnormal hyphal growth of the pathogen based on scanning electron micrograph observations. Six genera out of 18 promising antagonists were individually tested for the ability to degrade cellulose using the carboxymethyl cellulose (CMC) agar plate technique. High ratio of cellulolytic activity was exhibited by Mucor (101) and Aspergillus (79, 108) with similar ratio of 1.12, while Mortierella (177) and Cunninghamella (165, 168) were not able to degrade cellulose. The four promising antagonist isolates were individually tested for crude extract activity against the pathogen using the potato broth technique. Aspergillus (79) caused the lowest percentage of Zoospore germination of the pathogen (11.15%). The four promising antagonists were identified as Mucor racemosus (101), Gliocladium virens (109), Trichoderma harzianum (179) and Aspergillus flavus (79). Mucor racemosus (101) exhibited the highest PIRG (75.55%) of the pathogen and the highest inhibitory activity on the infection of P. capsici on leaves of black pepper, with leaf spot size of 2.39 mm in diameter. Antagonistic activity of G. virens (109), T. harzianum (179) and A. flavus (79) were not significantly different from each other