A Handbook of Rice Seedborne Fungi TW Mew and P ... - IRRI books

Microorganisms associated with seedNot all microorganisms associated with seed arepathogens. Some microorganisms possess biologicalcontrol properties. The occurrence of nonpathogenicXanthomonas has further complicated the issue ofseedborne bacterial pathogens. Cottyn et al (2001)and Xie et al (2001) proved that seedborne antagonisticbacteria are present in rice and promote seed germinationand seedling vigor, and also suppress diseasewith an inoculum from the seed. Microfloraassociated with the seed may be roughly categorizedinto pathogens and nonpathogens. The study byCottyn et al (2001), supported by the BelgiumAdminstration for Development Cooperation, andXie et al (2001) showed that rice seed carries manybacteria belonging to 17 genera and over hundreds ofspecies. Predominant were Enterobacteriacae(25%), Bacillus spp. (22%) and Pseudomonas spp.(14%). Other bacteria regularly present wereXanthomonas spp., Cellulomonas flavigena, andClavibacter michiganense. We found that about 4%of the total bacterial population possesses biologicalcontrol properties against most seedborne pathogens.Also, seedling vigor was enhanced after soakingseeds in bacterial suspension. These studies showthat rice seed not only carries pathogens but alsoabundant microorganisms that act as biological controlagents. Whether they play a bigger role in cropproduction and disease management needs furtherresearch. More support should be given to this researcharea, which is a vital part of a farmers’ internalresource management for sustainable crop productionand disease management.11