Identification of resistance sources in wild species of rice against two recently evolved pathotypes of Xanthomonas oryzae pv oryzae

Bacterial blight (BB) of rice caused by Xanthomonas oryzae pv. oryzae (Xoo) is a major biotic constraint of rice production in all the major irrigated/lowland rice growing regions of Asia, including Punjab and its adjoining states in India. None of the individual BB resistant Xa/xa genes is effective against Punjab pathotypes. In the present study, we have screened 1176 accessions, comprising 1007 accessions of A genome species Oryza glaberrima, O. barthii, O. nivara, O. rufipogon, O. longistaminata, O. meridionalis, O. glumaepatula and 169 accessions from ten other wild species having CC, FF, EE, BBCC and CCDD genomes against two most recently evolved Xoo pathotypes viz. PbXo-10 and PbXo-8 in Punjab state of India, for two constitutive years 2014 and 2015. Based on 2 years of data, four accessions of O. glaberrima (IRGC102206, IRGC1022445, IRGC102512 and IRGC102520) and two of the O. longistaminata accessions (IRGC92624 and IRGC101754) were identified with immune reaction against PbXo-8. For PbXo-10, O. longistaminata showed large number of accessions with complete to partial resistance followed by O. rufipogon (8), O. nivara (2), O. punctata (2) and O. officinalis (1). Two of the O. longistaminata accessions IRGC92624 and IRGC92644 from Mali were found to have resistance against both the Xoo pathotypes indicating presence of BB resistance gene other than Xa21. These can be transferred to elite cultivars of O. sativa for better management of BB.