INCIDENCE AND SEVERITY OF BROWN SPOT (BS), BACTERIAL LEAF BLIGHT (BLB) AND TUNGRO DISEASE IN MOSTLY CULTIVATED HYBRID AND INBREED RICE VARIETIES IN BANGLADESH

Abstract

Present studies had been conducted to evaluate the effect of different hybrid and inbreed varieties of rice against major field diseases during the period from December, 2013 to June, 2014. The experiment was conducted in the Agronomy Farm, Sher-e-Bangla Agricultural University, Dhaka-1207. Five Hybrid varieties namely BRRI Hybrid Dhan 2, BRRI Hybrid Dhan 3, Aloran, Jagoran, Shakti 2 and five Inbreed varieties namely BRRI Dhan 28, BRRI Dhan 29, BRRI Dhan 50, BINA 8 and BINA 10 were evaluated against incidence and severity of brown spot, bacterial leaf blight and tungro disease at three growth stages (40 DAT, 60 DAT and 80 DAT). The effect of diseases on yield and yield contributing characters were also observed. The incidence and severity of diseases varied significantly from one another. All the varieties were developed brown spot and bacterial leaf blight disease under field condition. At 80 DAT, among hybrid varieties the highest incidence and severity of brown spot was found in Aloran (incidence in hill, leaf, grain and severity in leaf 19.74, 6.62, 18.09 and 1.74% respectively) and BLB was recorded in Shakti 2 (incidence in hill, leaf and severity in leaf 16.67, 4.03 and 0.46 respectively). The lowest incidence and severity of both diseases viz. brown spot and BLB were observed in BRRI Hybrid Dhan 2. The highest yield was found in BRRI Hybrid Dhan 2 (10.46 t/ha), and lowest yield was recorded in Aloran (5.57t/ha) and Shakti 2 (7.43t/ha). Incase of inbreed varieties, the highest incidence and severity of brown spot was found in BRRI Dhan 29 (incidence in hill, leaf, grain and severity in leaf 16.66, 7.23, 19.29 and 1.41% respectively) and BLB was recorded in BRRI Dhan 28 (incidence in hill, leaf and severity in leaf 9.48, 3.89 and 0.46% respectively). The lowest incidence and severity of brown spot was observed in BRRI Dhan 50 and BLB was found in BINA 10. The highest yield (8.92 t/ha) was recorded in BRRI Dhan 50 and BINA 10 and lowest was found in BRRI Dhan 28 (4.74 t/ha) and BRRI Dhan 29 (5.43 t/ha). Incase of Tungro, rice green leaf hoppers (Nephotettix virescens) were inoculated on each varieties of rice except control plants to develop the disease. Among the hybrid varieties, BRRI Hybrid Dhan 3 and Aloran were found highly susceptible and Shakti 2 was recorded highly resistance to tungro disease followed by control plant. While in the inbreed varieties, BRRI Dhan 29 was found highly susceptible and BRRI Dhan 50 and BINA 8 were observed highly resistance to tungro followed by control plant. It was noted that, every infected plant of both types of varieties (Hybrid and Inbreed) initiated lower number of tiller and panicle than untreated plant and the tiller number with panicle number become decreases with the increase of disease incidence. In case of all diseases, it was observed that disease incidence and severity was gradually increased with the age of the plant and minimum incidence and severity gave the maximum yield.