Imposition of Pyricularia oryzae Stress on Growth and Yield of BRRI dhan29 and IR 64

Abstract

Rice blast, caused by Pyricularia oryzae, is one of the most significant fungal diseases of rice, affecting growth and yield worldwide. The impact of P. oryzae on two rice genotypes, BRRI dhan29 and IR 64 was selected based on their resistance level against Pyricularia oryzae. The experiment was carried out under controlled conditions during the Boro season in order to assess morphological, physiological, and yield-related parameters in both genotypes artificially inoculated and non-inoculated Pyricularia oryzae stress. The results of this experiment show that Pyricularia oryzae exhibits severe stress in both genotypes with regard to plant height, tiller number, fresh and dry biomass, and leaf area. BRRI dhan29 showed greater susceptibility compared to IR64 in all studied morphological and physiological parameters. Under inoculated conditions, IR 64 maintained greater effective tiller number plant⁻¹ (23) than BRRI dhan29 (11). In case of dry weight of biomass IR 64 showed a reduction of 13.42%, while BRRI dhan29 displayed a higher reduction of 19.95%. IR 64 had fewer unfilled grains (391) compared to BRRI dhan29 (600) under P. oryzae inoculated conditions. Grain filling drastically affected by Pyricularia oryzae stress in BRRI dhan29 (44.73%) compared to IR 64 experienced a smaller reduction (11.45%). Only 12.5% reduction was found in IR 64 considering thousand grain weight, whereas BRRI dhan29 exhibited a more significant reduction (37.60%). Yield-contributing traits, including panicle length, filled grain number, and thousand-grain weight, were also adversely affected which led to a higher yield loss in BRRI dhan29 (32%) compared to IR64 (10.96%). Leaf Area and leaf greenness by SPAD showed significant difference (P<0.05) in both rice genotypes at 15, 30, 45 and 60 days after inoculation. After 15 days of inoculation, IR 64 showed reductions in leaf area and leaf greenness of 8.21% and 4.13%, respectively, but BRRI dhan29 showed reductions in leaf area of 30.67% and leaf greenness of 34.25%. BRRI dhan29 had shown 50.94 % and 80.44% Percent Disease Index (PDI) respectively at 10 and 20 days after inoculation, which is noticeably greater than IR 64.Under Pyricularia oryzae stress, IR64 maintains better physiological performance and yield stability.