[01] B. Chaudhary, National Rice Research Program, Nepal Agricultural Research Council (NARC), Hardinath, Nepal. [02] S. M. Shrestha, Institute of Agriculture and Animal Science, Tribhuvan University, Rampur, Nepal. [03] U. S. Singh, International Rice Research Institute, New Delhi, India. [04] H. K. Manandhar, Nepal Agricultural Research Council (NARC), Kathmandu, Nepal. [05] N. W. Zaidi, International Rice Research Institute, New Delhi, India. [06] R. B. Thapa, Institute of Agriculture and Animal Science, Tribhuvan University, Rampur, Nepal. [07] N. K. Dangal, Regional Agricultural Research Station, Nepal Agricultural Research Council, Tarahara, Nepal.

Bacterial blight (BB) caused by Xanthomonasoryzaepvoryzae; is a major threat to rice production in Nepal. The disease is prevalent from terai to mid-hills causing variable reduction in grain yield and its quality. In terai, BB accompanied with flash floods in rainfed lowland and irrigated areas, posses frequent problems and severe crop loss in traditional and improved rice varieties. Recently, two rice varieties Swarna Sub1 and Samba Masuli Sub1 were released to mitigate the flash flood problem. A field experiment was conducted using these two Sub1 and two non-Sub1 rice varieties with their submerged and non-submerged seedlings to manage BB in a randomized complete block design during the 2013 and 2014 wet seasons at Regional Agricultural Research Station, Tarahara, Nepal. Use of submerged seedlings had a significant influence on BB disease severity and area under disease progress curve (AUDPC) values. The disease was significantly lower on plants transplanted after three to seven day submerged seedlings. The lowest BB was recorded on rice plants transplanted with seven day submerged seedlings. Disease reduction was more pronounced in Sub1 genotype when submerged seedlings were used. BB measured by AUDPC values and rice grain yield were negatively correlated with reduction of 5-6 kg ha-1 by one unit increase in AUDPC. Swarna Sub1 recorded the lowest BB as measured by disease severity and AUDPC values with or without use of submerged seedlings, and produced higher grain yield.

Submergence, Bacterial Blight of Rice, Disease Resistance, Flood Tolerance

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