Evaluation of Imported Hybrid Rice Varieties against Three Field Diseases under Natural Epiphytic Conditions of Bangladesh

An investigation was carried out to evaluate imported hybrid rice varieties against major field diseases under natural epiphytic conditions of Bangladesh during 2008-09. Fifteen hybrids (13 imported, 2 local) viz. Hira-1, Hira-2, ACI-1, Surma-1, Taj-1, Modhumoti-2, Krishan-2, Sonar Bangla-6, Richer-101, Moyna, Tia, Tinpata, Aloron, BRRI hybrid dhan-1, BRRI hybrid dhan-2 and 2 HYV check varieties viz. BRRI dhan-28 and BRRI dhan-29 were evaluated against disease incidence and severity of three seed borne field diseases viz. brown spot (Bipolaris oryzae), leaf blast (Pyricularia grisea) and narrow brown leaf spot (Cercospora oryzae) at three growth stages (flowering, milking and maturity). The effect of diseases on yield and yield contributing characters were also observed. The incidence and severity of diseases varied significantly from one another. The disease incidence and severity of brown spot at maturity stage were recorded from 15.51 to 25.85% and 0.64 to 4.15 (0-9 scale), respectively where Hira-2 and ACI-1 varieties showed good performance against the disease. In case of leaf blast, the disease incidence and severity ranged from 8.82 to 21.28% and 1.01 to 6.21 (0-9 scale), respectively at maturity stage where Hira-2 showed the lowest incidence (8.82%) and severity (1.01). Richer-101 showed the highest incidence (21.28%) and severity (6.21). In case of narrow brown leaf spot (maturity stage), the disease incidence and severity ranged from 6.27 to 12.23% and 1.10 to 5.84 (0-9 scale), respectively where the highest incidence (12.23%) and severity (5.84) was recorded on Modhumoti-2 and the lowest incidence (6.27%) and severity (1.10) was observed on ACI-1. The highest growth and yield contributing characters recorded on ACI-1, Hira-1 and Hira-2 considering plant height, panicle length, effective panicle and filled grain. Grain yield ranged from 4.50 to 10.77 t/ha. In case of hybrids, the highest grain yield (10.77 t/ha) was recorded on Hira-1. Hira-2 and ACI-1 also gave the better yield 9.72 t/ha and 9.70 t/ha, respectively. The lowest grain yield (7.90 t/ha) was found in Krishan-2 which was statistically identical with Richer- 101 (7.92 t/ha). It was observed that disease incidence and severity was gradually increased from flowering stage to maturity stage with the age of the plant and minimum incidence and severity gave the maximum yield.