Bacterial blight, blast, and brown spot are the commonest diseases causing substantial yield loss in rice around the world. Host plant resistance is most economic, durable, and ecofriendly approach to manage the plant diseases. The resistant cultivars developed through single resistant gene quickly lost its resistance and rendered susceptibility to the diseases. Therefore, harnessing the chemicals for the management of rice diseases is considered as the most efficient method. The present study was carried out at the experimental farm of TRRI, Aduthurai, Tamil Nadu, India during two consecutive years 2021 and 2022 to identify brown spot and bacterial leaf blight disease-resistant rice genotypes under field conditions. About 142 different rice genotypes were screened for resistance against brown spot and bacterial leaf blight for two years consecutively. The rice genotypes such as AD 17083, ADT 39, CB 16118, TPS 3, AD 18131, TRY 3, TR 05031, AD 16154, AD 18035, and Karuppukavuni exhibited moderate resistance to both diseases under natural field conditions. These genotypes may be further utilized as the genetic sources in multiple disease resistance rice breeding programmes. We also conducted the field experiments to evaluate the efficacy of different fungicides, bactericides, and their combinations against the rice diseases during 2021-2022. Combined fungicide application was effective in reducing the disease incidence of rice blasts and brown spots. For blast, Azoxystrobin 18.2% w/w+ Difenoconazole 11.4% w/w SC @ 0.1% was found to be most effective with a reduced disease incidence of 4.2 % compared to control. Meanwhile, for brown spot, the combined application of Carbendazim 25% + Mancozeb 63% @ 0.2% recorded the least disease incidence (10.36%). In Bacterial Leaf Blight incidence, Bionol @ 500 ppm was the most effective bactericide with the lowest incidence of 8.24%. It is evident from the current study, the tested fungicide combinations and bactericides proved the greater control over the pathogens with high yield.

Resistance, major rice diseases, artificial inoculation, antibiotics, fungicides

From the present study it is concluded that ten rice genotypes viz., AD 17083, ADT 39, CB 16118, TPS 3, AD 18131, TRY 3, TR 05031, AD 16154, AD 18035, and Karuppukavuni exhibited moderate resistance to Brown spot and BLB. Meanwhile, testing the efficacy of agrochemicals and antibiotics resulted that the Azoxystrobin 18.2% w/w+ Difenoconazole 11.4% w/w SC @ 0.1 % performed better controlling efficacy against paddy blast. For Brown spot, the application of Carbendazim 12%+ Mancozeb 63% WP @ 0.2% showed the lowest disease incidence. Similarly, Bionol (Bronopol 100%) @ 500ppm was effective against BLB under field conditions.

A. Ramanathan and R. Kanipriya (2023). Screening of Rice Genotypes and Evaluating the efficacy of Single and Combination Agrochemicals against Blast, Brown Spot and Bacterial Leaf Blight Diseases in Rice. Biological Forum – An International Journal, 15(8a): 429-437.