EFFECT OF SOME SELECTED SEED TREATMENTS ON MAJOR DISEASES AND YIELD ATTRIBUTES OF HYBRID RICE (Var. Taj-l) IN AMAN SEASON

Abstract

An investigation was carried out to evaluate the efficacy of some selected seed treatments on seed germination, seed borne pathogens, incidence and severity of major field diseases and yield contributing characters of imported hybrid aman rice (Taj-I) in the laboratory of Plant Pathology department and field of Sher-e-Bangla Agricultural University farm during the period from November 2009 to December 2010. Eleven seed treating agents viz. untreated control, sun drying, polythene solarization, brine solution, neem leaf extract, allamanda leaf extract, hot water treatment, Provax 200, Bavistin 50 WP, Dithane M 45 and Trichoderma harzianum were evaluated for their effect on seed germination and incidence of seed borne pathogens in vitro as well as disease incidence and severity at 3 stages and on yield contributing characters in vivo. Nine seed borne pathogens namely bacteria (unidentified), Rhizopus stolonifer, Aspergillus spp., Fusarium moniliforme, Phoma sp., Bipolaris oryzae, Curvularia lunata, Penicillium sp. and Alternaria tenuissima were recorded and identified in blotter and agar plate method of seed health study. In blotter and . agar plate method the highest ·seed germination (94.60%) and (91.45%), respectively were recorded under Dithane M 45 and the lowest (77.31 %) and (78.32%) were recorded under untreated control. The highest pathogen incidence was observed under untreated control and all the treatments significantly reduced the pathogen incidence except polythene solarization and sun drying treated seed. Dithane M. 45, Bavistin 50 WP, Provax 200 and hot water treatment showed the best performance in reducing seed borne pathogen incidence in both the methods of seed health testing. Five field diseases viz. brown spot (Bipolaris oryzae), narrow brown spot (Cercospora oryzae), leaf blast (Pyricularia grisea), BLB (Xanthomonas campestris pv. oryzae), and sheath blight (Rhizoctonia solani) were recorded and identified. The disease incidence and severity of brown spot at maturity stage were recorded from 5.48% to 13.89% and 0.91 to 1.67 (0-9 scale), respectively where Dithane M 45, Bavistin 50 WP and Provax 200 showed good performance against the disease. In case of leaf blast, the disease incidence and severity ranged from 5.96% to 16.11% and 2.63 to 5.86 (0-9 scale), respectively at maturity stage where hot water treatment showed the lowest incidence (5.96%) and severity (2.63). Disease incidence and severity of sheath blight varied from 15.87% to 20.30% and 6.47 to 7.80 (0-9 scale), respectively at maturity stage where hot water treatment showed the best result against the disease. Provax 200 was also effective followed by hot water treatment. In case of BLB, the disease incidence and severity ranged from 13.62% to 23.20% and 5.64 to 8.29 (0-9 scale), respectively at maturity stage where none but hot water treatment was effective against the disease. In case of narrow brown leaf spot, the disease incidence and severity ranged from 1.49% to 7.79% and 0.63 to 3.44 (0-9 scale), respectively at maturity stage where three fungicides and hot water treatment effectively managed the disease.The highest growth and yield contributing characters were recorded under the fungicidal seed treatment followed by hot water treatment considering plant height, panicle length, effective panicle and filled grain. Grain yield ranged from 7.27 t/ha to 10.40 tfha. Under different treatments, the highest grain yield (10.40 t/ha) was recorded under Dithane M 45 followed by Bavistin 50 WP and Provax 200. The lowest grain yield (7.27 t/ha) was found under polythene solarization which was statistically identical with untreated control. 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.