INTRODUCTION Rice is one of the major food crops of the world especially that of the South Asian countries like India, Pakistan, Bangladesh, China, Vietnam and Korea. It is a staple food in India, and occupies a prime position in the country’s economy (Srinivasan and Gnanamanickam 2005). Bacterial leaf blight (BLB), caused by Xanthomonas oryzae pv. Oryzae (Xoo) is one of the most destructive diseases of rice occurring throughout the world (Swings et al., 1990; Ishiyama, 1922; Mew et al., 1993). The incidence of Xoo limits the production of this staple food of more than half the world’s population (Salim et al., 2003). BLB became serious due to the introduction of improved, high yielding varieties, with high nitrogen requirement, close spacing and inadequate resistance to Xoo (Eamchit and Mew 1982). The disease was first noticed in Fukuoka prefecture of Kyushu Island, Japan, in 1884-85 (Ezukaand Kaku, 2000). In India, BLB was first noticed from Koloba district of Maharashtra, during 1959 (Srivastava and Rao 1966). In general, the disease is reported to be responsible for a yield loss of 20-50 per cent, depending upon stage of the crop, severity of infection, weather conditions and cultivar response (Srivastava, 1967; Amna, 2008). The disease is known to occur in epidemic form in many parts of the world, causing losses to the extent of 6-60% or even upto 81% in some cultivars (Shehzad et al., 2012). BLB adversely affects grain filling and emergence of panicles, about 28-30% yield reduction was observed in susceptible cultivars by Shahjahan et al. (1991). The disease appears at all the growth stages of the crop, initiating two main symptoms i.e., leaf blight or wilt or Kresek and yellow leaf (Gnanamanickam et al., 1999). The main symptoms of the disease are water soaked stripes along the margin of leaf blades, which later on enlarge and turn yellow. These lesions may cover the entire blade, and may extend to the lower end of leaf sheath. Similar symptoms may occur on glumes of green grains. The causal organism (Xoo) survives in the rhizosphere of weed hosts, infected straw and root stubble and disseminate by wind and water (Shahjahan et al., 1991).Chemical control of BLB is not feasible due to non-availability of effective bactericide (Khush et al., 1989). Though biocontrol agents have been reported to manage the disease to some extent, but their field application is not widely adopted (Khush et al., 1989). Therefore, identification of resistant source against the disease is the most effective, eco-friendly and sustainable approach to manage the disease. The efficiency of breeding for resistant programme is mainly dependent on two important variables, availability of resistant genetic sources and variation within the pathogen population. Breeding for resistance is thus the best option to encounter the disease (Chen et al., 2002). The availability of several genes responsible for resistance may help the breeders to go for various breeding strategies like gene rotation, gene deployment and gene pyramiding. Therefore, the present study is aimed to evalualate rice germplasm for exploring the source of resistance against bacterial leaf blight. MATERIALS AND METHODS The present investigation was undertaken to find the resistant sources of rice against BLB, at Research Farm, SKUAST-J, Chatha, during Kharif 2019 and 2020 under epiphytotic conditions. Ninety one germplasm lines (US-317, HRI-201, ARRH-23664, IIRRH-130, PR-124, IRH-121, SHX-468, RRX-533, USD-339, JKRH-2789, IIRRH-131, MUTUHR-2104, Gontra Bindhan-3, RRX-445, RH-169257, PHI-19106, IIRRH-135, CRHR-122, RNE-0148, HRI-174, NDR-359, US-308, MTUHR-2107, CRHR-145, TNRH-294, JKRH-3333, 27P63, WGL-14, L9-19201, LP-18204, RRX-719, WGRH-18, MR-8222, RH-169269, CRHR-105, CRHR-106, SAVA-5065, MP-3020, NK-5251, RNC-0050, IRH-120, IIRRH-136, IRH-122, US-312, TMRH-5559, MEPH-153, RRX-426, US-368, PHI-19103, RH-169292, IIRRH-134, RNE-0122, IIRRH-137, CRHR-148, DLRH-6, PR-121, MEPH-155, NPH-X28, PHI-19101, MTUHR-2105, TNTRH-99, Improved Samba Mahsuri, RRX- 556, NPX-X4, RH-169035, US-314, CO-51, NPH-101, SAVA-5055, Indam-300-007, LP-19301, US-326, PHI-19107, RRX-633, PHI-19108, Basmati-370, RNC-0158, IIRRH-132, IIRRH-133, PR-113, NPH-X29, HRI-202, PHI-19104, PHI-19105, MP-3310, CP-800, IIRRH-138, HRI-203, CRHR-150, BPT-520 and MEPH-152) were collected All India Coordinated Rice Improvement Programme (AICRIP) Centre, Division of Genetics and Plant Breeding, Faculty of Agriculture, SKUAST-Jammu, Chatha during Kharif season of 2019-2020 for screening against BLB under epiphytic conditions. Whereas, one hundred four germplasm of rice (KAVERI-7299, UPLRH -179510, RRX-848, JGL-275, US-330, US-314, PR-124, Ranbir basmati, NPH-X628, JKRH-2709, PHI-20102, PHI-20104, US-348, MEPH-157, PR-113S-7004, VNR-225, RRX-890, DLRH-9, MEPH-158, MEPH-159, HRI-174 (NCH), SJR 5, KAVERI- 7623, RRX-708, US-310, JKRH-3333 (NCH-1), 27P63 (NCH-2), WGL-14 (NCV-1), IR-64, RP-BIO-226,IR-50, Swarnadhan, HRI-207, NPH-X73, YPH-4009, UPLRH-179524, TMRH-21210, MP-3110, Pusa RH-59, VNR-227, RALLIS-19303, PHI-20103, RRX-809, NS-1202, RNRH-12, Pusa RH-61, IIRRH-144, RNRH-18, US-357, IRH-126, TNRH-303, US-312 (NCV), Basmati-370, KAVERI-7425, PHI-20106, PHI-20109, US-375, IIRRH-145, NRH-30, NDR-359 (NCV), PR-121, Sava- 3701, HRI-206, GK-5003 Pro, NPH-X63, VNR-226, Improved Samba Mahsuri, HR-12, Nidhi, Benibhog, Ajaya, Tetep, PAN-2430, JKRH-1601, PHI-20101, Pusa RH-60, MEPH-156, CO-51 (NCV), HRI-208 NPH-X5, S-4003, YPH-4129, UPLRH-179520, UPLRH-162122, RRX-805, IRH-124, IIRRH-143, RNRH-78, Gontra Bidhan-3 (NCV), HRI-204, Marshal-135 Pro, HRI-205, PHI-20107, PHI-20108, IIRRH-146, TN1 RALLIS-19608, MEPH-161, BPT-5204 (NCV2), Vikramarya, CH-45, CO-39 and KAVERRI-7317) were also collected from All India Coordinated Rice Improvement Programme (AICRIP) Centre, Division of Genetics and Plant Breeding, Faculty of Agriculture, SKUAST-Jammu, Chatha during Kharif season of 2019-2020 for screening against BLB under epiphytic conditions. The seedlings of these germplasm were raised in nurseries on first week of July during 2019 and 2020, adopting all the normal agronomic practices. Transplanting was done on 7th August, 2019 and 10th August, 2020. Each germplasm was grown in two rows of 2 m length, with row to row spacing of 50 cm and plant to plant spacing of 15 cm. Ten plants of each germplasm/variety were randomly selected and tagged for recording observations on the severity of BLB. For creating/initiating disease, 30th days after transplanting, individual plants were inoculated with three-day old culture of Xoo, multiplied on nutrient broth (Kauffman et al., 1973). Irrigation was given immediately after the inoculation to create high humidity for build-up of infection. Disease severity was recorded on 1-9 scale at tillering stage. Percent average lesion area of leaves were measured for disease severity using the following scale: n= Number of leaves showing severity score of 1, 3, 5, 7, 9 tn = Total number of leaves scored Disease response Scale used for assessing disease severity of bacterial blight of rice (IRRI, 2004). RESULTS AND DISCUSSION Screening of rice genotypes against bacterial leaf blight of rice during kharif 2019. Based on disease reaction, 91 germplasm lines obtained from Indian Institute of Rice Research, Hyderabad, were grouped into five categories i.e. resistant, moderately resistance, moderately susceptible and susceptible (Table 1, 2). None of the germplasm lines expressed resistant reaction while, 28 lines (US-317, HRI-201, ARRH-23664, IIRRH-130, PR-124, IRH-121, SHX-468, RRX-533, USD-339, JKRH-2789, IIRRH-131, MUTUHR-2104, Gontra Bindhan-3, RRX-445, RH-169257, PHI-19106, IIRRH-135, CRHR-122, RNE-0148, HRI-174, NDR-359, US-308, MTUHR-2107, CRHR-145, TNRH-294, JKRH-3333, 27P63, WGL-14) showed moderately resistant reaction. The disease severity for moderately resistant varieties varies between 5.69- 11.91 per cent. Thirty four germplasm lines (L9-19201, LP-18204, RRX-719, WGRH-18, MR-8222, RH-169269, CRHR-105, CRHR-106, SAVA-5065, MP-3020, NK-5251, RNC-0050, IRH-120, IIRRH-136, IRH-122, US-312, TMRH-5559, MEPH-153, RRX-426, US-368, PHI-19103, RH-169292, IIRRH-134, RNE-0122, IIRRH-137, CRHR-148, DLRH-6, PR-121, MEPH-155, NPH-X28, PHI-19101, MTUHR-2105, TNTRH-99, Improved Samba Mahsuri) showed moderately susceptible reaction, having disease severity between 14.61- 24.67 per cent. Twenty eight germplasm lines (RRX- 556, NPX-X4, RH-169035, US-314, CO-51, NPH-101, SAVA-5055, Indam-300-007, LP-19301, US-326, PHI-19107, RRX-633, PHI-19108, Local Check Variety (LCV), RNC-0158, IIRRH-132, IIRRH-133, PR-113, NPH-X29, HRI-202, PHI-19104, PHI-19105, MP-3310, CP-800, IIRRH-138, HRI-203, CRHR-150, SJR5, Basmati 370, Ranbir Basmati BPT-520) showed susceptible reaction, with disease severity ranging between 25.21- 45.63 per cent. One germplasm line (MEPH-152) showed highly susceptible reaction, having disease severity of 69.47 per cent. Screening of rice genotypes against bacterial leaf blight during kharif 2020. During 2020 also, based on their reaction towards the disease, 104 germplasm lines were grouped into five categories i.e. resistant, moderately resistance, moderately susceptible and susceptible. Data presented in Table 3 and 4 indicate that none of the germplasm lines expressed resistant reaction, while, 33 lines (KAVERI-7299, UPLRH -179510, RRX-848, JGL-275, US-330, US-314, PR-124, Local Check Variety (LCV), NPH-X628, JKRH-2709, PHI-20102, PHI-20104, US-348, MEPH-157, PR-113S-7004, VNR-225, RRX-890, DLRH-9, MEPH-158, MEPH-159, HRI-174 (NCH), Local Check Variety (LCV), KAVERI- 7623, RRX-708, US-310, JKRH-3333 (NCH-1), 27P63 (NCH-2), WGL-14 (NCV-1 ) IR-64, RP-BIO-226, IR-50 and Swarnadhan) showed moderately resistant reaction, with disease severity varying between 7.43-11.98 per cent. Thirty nine lines (HRI-207, NPH-X73, YPH-4009, UPLRH-179524, TMRH-21210, MP-3110, Pusa RH-59, VNR-227, RALLIS-19303, PHI-20103, RRX-809, NS-1202, RNRH-12, Pusa RH-61, IIRRH-144, RNRH-18, US-357, IRH-126, TNRH-303, US-312 (NCV), Local Check Variety (LCV), KAVERI-7425, PHI-20106, PHI-20109, US-375, IIRRH-145, NRH-30, NDR-359 (NCV), PR-121, Sava- 3701, HRI-206, NPH-X63, VNR-226, Improved Samba Mahsuri, HR-12, Nidhi, Benibhog, Ajaya and Tetep) showed moderately susceptible reaction, with disease severity of14.62-23.65 per cent. Thirty one lines (PAN-2430, JKRH-1601, PHI-20101, Pusa RH-60, MEPH-156, CO-51 (NCV), HRI-208, GK-5003 Pro, NPH-X5, S-4003, YPH-4129, UPLRH-179520, UPLRH-162122, RRX-805, IRH-124, IIRRH-143, RNRH-78, Gontra Bidhan-3( NCV), HRI-204, Marshal-135 Pro, HRI-205, PHI-20107, PHI-20108, IIRRH-146, RALLIS-19608, MEPH-161, BPT-5204 (NCV2), Vikramarya, TN1, CH-45 and CO-39) showed susceptible reaction, with disease severity of 27.56-46.78 per cent. One germplasm line (KAVERRI-7317) showed highly susceptible reaction having disease severity of 78.41 per cent. DISCUSSION Identification of resistance source is the key factor in developing rice resistant cultivar against BLB. While screening the rice germplasm against Xoo, it was recorded that out of 104 germplasm lines screened during kharif 2019, none of the germplasm line expressed resistant reaction while, 28 lines showed moderately resistant reaction, 34 lines were moderately susceptible, 28 lines had susceptible reaction, and one germplasm line showed highly susceptible reaction. Similarly, during kharif 2020, none of the germplasm line expressed resistant reaction, while 31 lines showed moderately resistant reaction, 38 lines showed moderately susceptible reaction, 34lines showed susceptible reaction, and one germplasm line showed highly susceptible reaction. During 2019, out of total germplasm, 30.76 percent were moderately resistant, 37.36 percent moderately susceptible, 30.76 percent showed susceptible and 0.01098 percent highly susceptible reaction towards BLB. Similarly during 2020, out of total germplasm lines 31.73 percent were moderately resistant, 37.5 percent moderately susceptible, 29.80 percent susceptible and 0.009 percent highly susceptible. Variation in reaction of germplasm lines towards the disease may be explained by the fact that they had different genetic makeup. Varietal differences in susceptibility of rice plant to BLB have been well demonstrated by many workers (Ardel- hak et al., 1982; Prasad and Singh, 1985; Prasad et al., 1998; Chauhan et al., 2000; Mashraff et al., 2004 and Anita et al., 2005).Screening of 71 rice germplasm against Xoo exhibited that Siruguppa, 3 genotypes viz., Ajaya, TKM-6 and IR-8 were resistant IR-72, Tetep, PR-111, Zenith, CRMAS-2231-23 and Govind were moderately resistant, whereas, 23 were moderately susceptible, 24 were susceptible and 15 were highly susceptible (Thimmegowda et al.,2011). Screening of 522 rice lines against Xoo showed 16 lines as resistant, 70 as moderately resistant, while the remaining were either susceptible (95) or highly susceptible (341) (Pandey et al.,1999). Evaluation of 104 local rice varieties/lines for resistance to Xoo under field conditions, from 1996 to 1998, showed that IR64, IR8 and Shadab were moderately resistant, while 50, 44 and 7 genotypes showed moderately susceptible, susceptible and highly susceptible response against the Xoo, respectively (Tasleem-uz-zaman et al., 2000). Out of eleven rice genotypes evaluated for resistance against BLB, PARC-301 was the most resistant, having least disease score, followed by PARC-293, PARC-294, PARC-298, PARC-299 and PARC-300 which were statistically at par (Waheed et al., 2009). Screening of 55 varieties against Xoo, exhibited that, 26 varieties were resistant against the disease. IR-72102-3-107-1-1-2 and P-52-9-2 were found moderately resistant and DM-1-30-3-99 was found moderately resistant (Khan et al., 2009). Out of 40 rice genotypes screened against Xoo, none showed significantly resistant response against the pathogen, only six were moderately resistant, eight were graded as moderately susceptible, while 19 were susceptible and six highly susceptible (Naqvi et al., 2015). Screening of 11 rice genotypes against Xoo showed that 4 genotypes as resistant, 3 were moderately resistant and 4 were moderately susceptible (Nahiyan et al., 2016).Field screening of 150 rice genotypes for resistance against BLB was done under natural condition during 2018 and 2019. During 2018, 6 genotypes exhibited resistant (R), 81 moderately resistant (MR), 59 moderately susceptible (MS) and 4 susceptible (S) response. While, in 2019, among the tested 315 rice genotypes, none of the genotypes were resistant, 183 were moderately resistant, 131 moderately susceptible and 1 susceptible reaction to BLB (Acharya and Sujata 2021).