Effect of Sowing Times and Rice Varietal Resistance on the Severity of Narrow Brown Leaf Spot Disease in Relation to Environmental Conditions

The objective of this study was to investigate the effects sowing times and genetic resistance 10 commercially important rice varieties on percent disease severity (PDS) narrow brown leaf spot (NBLS) caused by Cercospora oryzae. Two time treatments (mid-May mid-June) each year were evaluated for 2-year study. Rice drill seeded arranged in randomized complete block designed plots with four replications variety. environmental factors (high low temperature, relative humidity precipitation) NBLS at both also evaluated. Disease data analyzed using computer software GenStat 10th edition. Results: By changing cultivation timing varieties, B-Chenab, KSK-434, PK-386, B-Kissan, KSK-133 from mid-May mid-June, their levels changed a higher lower. Weather conditions during mid-June 2019 induced level than did weather 2018. variation temperatures affected more as compared precipitation. High temperature 31-33˚C 18-21˚C found be most effective enhancing development. Minimum 4.75% 8.25% noted variety B-515 sowings respectively. Thus, its rating resistant mildly susceptible timing. PK-1121 depicted maximum 60.25 % sowings, rated very highly susceptible, while increased 79.25% completely susceptible. It is concluded that thus consideration these key integrated management rice.