Response of rice genotypes to bacterial leaf streak caused by Xanthomonas oryzae pv. oryzicola, an emerging threat in Nepal.

Bacterial leaf streak (BLS) is one of the devastating diseases of rice in Asia, Northern Australia, and West Africa that leads to up to 32% yield losses. Previously, BLS was rare in Nepal, but it has become more common in recent years, and it is supposed to cause significant yield losses. However, studies on various aspects of BLS of rice, such as yield loss assessment, management strategy, germplasm evaluation, etc., have not been done in Nepal. Therefore, realizing the fact that the identification of resistant genotypes is a cost-effective and efficient approach to managing crop diseases; seventy-six rice genotypes were evaluated, along with resistant (Sabitri) and a susceptible (TN1) checks (usually used for bacterial leaf blight) under artificial epiphytotic conditions at the National Wheat Research Program (NWRP), Bhairahawa, Nepal, in the year 2018 and 2019. This study identified thirteen resistant and fourteen moderately resistant genotypes based on the mean percentage of disease severity over two years. The resistant genotypes viz., IR 108196-1-B-B-3-2-5, IR 10A 134, NR 2168-44-2-1-1-1-2-1-1, B 11598C-TB-21-B-7, IR 14D 198, IR 96279-39-3-1-2, IR 103587-22-2-3-B, BP 9474C-1-1-B, IR 10L 185, IR 15L 1735, IR 106529-20-40-3-2-B, IR 15D 1031 and IR 108541:1227-1-3-B-B could be used as resistance sources in the breeding programs. Furthermore, resistant genotypes with high yield potential after evaluation across different environments could be released as BLS resistant varieties in Nepal. This study may be the first effort to identify resistant rice genotypes, particularly against BLS, which is an emerging potential threat to rice production in Nepal.