INTRODUCTION Rice is the oldest cereal grain in the world. “Rice is life” for more than half of humanity. It has shaped the culture, diets, and economy of millions of people (Gnanamanickam et al., 2009). In the Asian subcontinent, 90 percent of the world’s rice is grown and consumed. Rice accounts for a significant contribution to the total food grain production in India. Rice is a staple food crop for more than half of the world’s population. In the Indian subcontinent more than a quarter of the cultivated area is under rice cultivation. India has 43.78 million hectares of area under cultivation and 121.46 million tonnes of production with average productivity of 2.55 tonnes per hectare from 2019-20 (Ministry of Agriculture and Farmer welfare). In Odisha, about 69% of the cultivated area comes under rice cropping,and is the major crop, covering about 63% of the total area under food Grains. The total area covering rice in Odisha is 3.9 million hectares, production is 9.63 million tonnes and productivity is 2.45 tonnes/ha in 2019-20 (Odisha Agricultural statistics, 2020). Plant diseases play a role as one of the major limitations in rice cultivation. Among all the rice infesting diseases, bacterial leaf blight is an important disease. Depending upon the stage of the crop, cultivar susceptibility, and environmental conditions, bacterial leaf blight can cause severe yield losses of up to 50% (Mew, 1987). No effective chemical control measures have been found against bacterial blight (Devadath 1989), so the use of resistant varieties is the only way to protect the crop from bacterial blight. Marker-assisted selection (MAS) has come into sight as a new field in Plant Breeding i.e., gene pyramiding for the advancement of broad-spectrum resistance abilities. Maximum no. of the presently cultivated popular Indian rice cultivars are facing problems due to various biotic and abiotic stresses. Pratikshya is a ruling rice variety of Odisha, India. However, it is susceptible to bacterial leaf blight (BLB) infection. In this circumstance, for attaining durable resistance it is essential to pyramid multiple genes. The present study has been undertaken to determine the level of resistance to bacterial leaf blight of rice induced by Xanthomonas oryzae pv. oryzae (Xoo) inocula to identify plants resistant to bacterial leaf blight in BC2F2 segregating population obtained from gene pyramiding of Pratikshya × Swarna MAS. MATERIALS AND METHODS Experimental materials are composed of two varieties of rice viz., Pratikshya and Swarna MAS. These two varieties were used to develop the backcross population (BC2F2 population) consisting of 1598 plants. Previously identified resistant parent ‘Swarna MAS’ was used as donor parent to transfer bacterial leaf blight resistance carrying xa5, xa13, and Xa21 genes to susceptible parent Pratikshya. Twenty-one days old seedlings were transplanted with a spacing of 20 × 20 cm. The recommended packages of practices were followed to raise a healthy crop. Bacterial Culture and inoculation. The isolates of Xanthomonas oryzae pv. oryzae (Xoo) was procured from Crop Protection Division, National Rice Research Institute, Cuttack. From the stock culture, the isolate was sub-cultured and maintained at 4°C for further use. On slants of Wakimoto’s medium for 3 days at 30°C cultures were grown (Table 1). By suspending the bacterial mass in sterilized distilled water inoculum was prepared and diluted to a concentration of about 109 cells/ml. The freshly prepared inoculum was utilized for inoculation. The leaf clip inoculation method developed at the AllIndia Coordinated Rice Improvement Project (AICRIP) was implemented at the maximum tillering stage of the screening population (Kauffman et al., 1973). The top of the fresh leaves of each plant was cut with a sterilized scissor dipped in freshly prepared bacterial solution as presented in Fig. 1 (A) early in the morning. Observations were noted 14-21 days after inoculation by the percentage of diseased leaf area (DLA) followed by the standard evaluation system (SES, IRRI, 2013). Noor et al. (2021) utilized followed this method for the screening of black rice races of Manipur for blight resistance. Scoring of the disease was done as shown in Table 2. RESULT AND DISCUSSION The bacterial leaf blight of rice is the most destructive affliction of cultivated rice. It is also a destructive disease in South and Southeast Asia. Depending on the severity of the infection, the loss may be as high as 50-80% (Khus, 1989). To minimize the severe attack and yield loss, some management strategies are needed through the development of BLB-resistant cultivars. However, none of the modern cultivars are completely resistant to this disease. Host plant resistance offers the most effective, economical, and environmentally safe option for the management of bacterial leaf blight (Khush et al., 1989). To date, 46 bacterial leaf blight resistance genes have been identified and some of them have been incorporated into the modern popular high yielding varieties of rice (Pradhan et al., 2015; Chen et al., 2020; Chukwu et al., 2019; Hsu et al., 2020). In the present study, the segregating backcross population has been evaluated for the presence of resistance genes in the plants. Out of 1598 plants, 1412 plants were found resistant 186 were susceptible. Bacterial leaf blight scores 1, 3, and 5 were considered as a resistant class while those having scores 7 and 9 with disease severity very much nearer to recurrent parent were considered as a susceptible class. These values indicated goodness of fit with an expected ratio of 55:9. The chi-square value for the expected value was obtained as non-significant at a 1% level of significance of probability (Table 3). This ratio indicated the presence of three resistance genes in the plant of the BC2F2 population. This can be explained by considering that bacterial blight resistance is governed by three genes xa5, xa13, and Xa21. So, the genotype and phenotype of a parent, F1, and BC2F2 would be as follows: Phenotypic data based on the leaf clip inoculation method separates the whole population into resistance and susceptible classes. Based on disease severity and similarity of agronomic characters with recipient parent Pratikshya, thirty-five superior plants were randomly selected from the BC2F2 population.