Advances in theXoo-rice pathosystem interaction and its exploitation in disease management

Bacterial blight caused byXanthomonas oryzaepv.oryzae(Xoo), is one of the devastating diseases of rice worldwide. The pathogen reported to cause 70% crop loss in some of the susceptible genotypes under disease favoring environments, viz., temperature ranging between 25 to 34 degrees C and relative humidity more than 70%. InXoo, about 245 genes govern the pathogenicity and host specificity. The hypersensitive response and pathogenicity (hrp) genes responsible for disease occurrence were clustered in the pathogenicity island of 31.3 Kb. The protein secreted through type three secretory system and type one secretory system mediates infection and establishment of the pathogen inside the host. However, elicitor molecules fromXootriggered the resistant response in rice against the pathogen. An array of resistant genes (Rgenes) was known to be invoked by the host to combat the bacterial infection. To date, of the 45Xagenes in rice, nine were cloned and characterized. The evolution of new races has made the task of developing resistant rice genotypes more challenging as it demands a comprehensive breeding strategy involving the best use ofRgenes from the existing gene pool. Thus, to combat the infection from the existing races and to slow down the emergence of newXooraces, pyramiding two or moreRgenes was found to be effective against bacterial blight disease. In India, the successfully commercialized example includes the development of rice genotypes, viz., Improved Pusa Basmati-1, Improved Samba Mahsuri, PR106, Type 3 Basmati, and Mahsuri with selectedRgenes, viz.,xa5,Xa4,xa13andXa21against bacterial blight resistance. This review primarily portrayXoo-rice interactions and provides opportunities for its effective management through sustainable technologies.