Vol.:(0123456789) 1 3 Indian Phytopathology https://doi.org/10.1007/s42360-020-00284-1 RESEARCH ARTICLE Screening for novel rice sheath blight resistant germplasm and their biochemical characterization S. Lalitha Pavani 1  · Vineeta Singh 1  · Sanjay Kumar Goswami 2  · P. K. Singh 3 Received: 18 February 2020 / Revised: 26 September 2020 / Accepted: 3 October 2020 © Indian Phytopathological Society 2020 Abstract Rhizoctonia solani Kuhn causes sheath blight of rice which is a common and destructive disease. The present studies focus on screening of rice genotypes against R. solani to fnd out promising sheath blight resistant genotypes and the role of the defense-related biochemical enzymes in six diferent moderately resistance, moderately susceptible and susceptible germ- plasm lines. A total of 196 rice germplasm lines were used to conduct a feld trial to screen sheath blight resistant germplasm during 2014–2015 and 2015–2016 crop seasons. The study identifed 33.1% moderately resistant, 55.6% moderately sus- ceptible and 11.2% susceptible genotypes to sheath blight in rice. Moderately resistant cultivar IC281785 recorded higher peroxidase activity (2.990) than moderately susceptible cultivar IC282450 (1.232). Higher PPO enzyme activity was observed in Tetep (1.729) followed by IC281785 (1.423) after 24 h of inoculation. Similarly, PAL activity was highest in moderately resistant cultivars than moderately susceptible and susceptible cultivars. The highest catalase activity was observed in mod- erately resistant cultivar Tetep (0.963) than susceptible cultivar PB1 (0.513) after 72 h of pathogen inoculation. Keywords AUDPC · Biochemical · Enzymes · Genotypes · Resistance · Rhizoctonia solani · Rice · Screening Introduction Rice (Oryza sativa L.) is a basic food for millions of peo- ple and has considerable importance in food and nutritional security. Rice production in the world has a several con- straints which may be grouped as the biotic and abiotic stresses. Biotic stress includes losses due to insect pests and pathogens. The pathogen R. solani Kuhn [Teleomorph Than- atephorus cucumeris (Frank) Donk], causes sheath blight of rice which is a widely spread disease causing great loss in quantity and quality of rice in all over the world (Lee and Rush 1983). According to Bhunkal et al. (2015) 4–50% yield loss had been reported depending on the infection time, the severity of the disease and environmental conditions. Since there are no disease resistant varieties available for sheath blight, the disease can be controlled by the use of chemical fungicides which are efective against sheath blight disease. But these chemicals are harmful to the environment. The best method of controlling the disease is the use of resistant varieties. Although highly sheath blight resistant rice varie- ties are not available, but few genotypes like Jasmine 85, Tetep, Teqing, Minghui 63, LSBR5, LSBR33 and Pecos, showed promising resistance against the disease (Srini- vasachary et al. 2011). Plants protect themselves by defense responses during the infection by pathogens. Bradley et al. (1992) showed a correlation between increased peroxidase (PO) activity and resistance in plants. Similarly, polyphe- nol oxidase (PPO) accumulates in wounded plants to resist the pathogen attack. The studies showed that phenylala- nine ammonia lyase (PAL) activity is also essential for the accumulation of phenolics in an infected plant (Klessig and Malamy 1994). The plants have also developed antioxidant defense systems to control ROS (reactive oxygen spp.) out- burst, consisting of ROS scavenging enzymatic antioxidants, Electronic supplementary material The online version of this article (https://doi.org/10.1007/s42360-020-00284-1) contains supplementary material, which is available to authorized users. * Vineeta Singh vineeta19744@yahoo.com 1 Department of Mycology and Plant Pathology, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi 221005, India 2 ICAR-Indian Institute of Sugarcane Research, Rai Bareli Road, Dilkusha, Lucknow, Uttar Pradesh 226002, India 3 Department of Genetics and Plant Breeding, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi 221005, India