Recent studies using antagonism and induced resistance to control
rice bacterial leaf blight, rice bakanae and shallot bulb rot

This paper presents the recent results of the Plant Pathology Research Group at Can Tho University during 2020. Six bacterial strains showing high disease-reducing effects against rice bacterial leaf blight (Xanthomonas oryzae pv. oryzae) were identified as Bacillus safensis AG-131, B. stratosphericus AG-62, B. aerophilus HG-33, B. pumilus TG-71, B. subtilis ST-115 and Serratia nematodiphila CT-78. The effects involve not only antagonism but also induced resistance. Indeed, treatments with the bacterial strains increased activities of the four enzymes in rice plants, i.e., phenylalanine ammonia-lyase, polyphenol oxydase, catalase and peroxiadse. These enzymes are responsible for defence respsonses against the disease. Formulation study has therefore been carried out to make bio-control products. Different carrier materials were tested to select those capable of maintaining bacterial cell densities, the antagonistic and disease-reducing effects after storage. Those of the Bacillus spp. were shown to be well maintained after 12-month storage in the carrier materials suplemented by yeast extract. For rice bakanae (Fusarium moniliforme), the two bacterial isolates VT-23 and CTA-30 showing high antagonistic and disease-reducing effects under greenhouse conditions were selected and identified as Bacillus haikouensis and B. safensis. For shallot, different pathogens causing bulb rot have been identified, among those, Citrobacter murliniae has additionally been identified causing the disease. The bacterial isolate CT-21 showing high antagonistic and disease-reducing effects under greenhouse conditions was selected for further disease control study.