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Open access Aug 2026

Morphological and Molecular Screening for Bacterial Leaf Blight Resistance in Land Races of Rice (Oryza sativa L.)

Bacterial leaf blight (BLB) of rice, caused by Xanthomonas oryzae pv. oryzae, is a major constraint on rice production, and the use of resistant genotypes is an important approach to disease management. The present study screened 40 rice genotypes for BLB resistance using morphological evaluation and molecular markers linked to seven resistance genes: xa5, Xa7, xa8, Xa10, xa13, Xa21 and Xa33. Field screening was conducted at RARS, Maruteru, during kharif 2023 using artificial inoculation by the leaf-clipping method, and disease reactions were assessed according to the Standard Evaluation System. Morphological screening categorised entries as highly resistant, resistant, moderately resistant, susceptible or highly susceptible according to diseased leaf area. Molecular screening was performed using gene-linked markers to determine the presence of the target resistance genes. Nineteen genotypes were identified as carrying two or three BLB resistance genes. Phenotypic evaluation based on diseased leaf area showed variation in resistance among the 40 genotypes and supported the molecular screening results. Jaavepula-2, Basmati, Tulasi baso and Kundadam-2 carried three resistance genes, while Kalamuch and Loyamalli carried the Xa7 and Xa21 combination and exhibited phenotypic resistance. The combined morphological and molecular screening therefore identified rice genotypes with multiple BLB resistance genes that may serve as donor parents in marker-assisted breeding programmes aimed at improving BLB resistance in rice.

J. Mounika, B. Veni, Rani Chapara et al. · 0 citations
Open access Jun 2026

Identification of Elite Rice (Oryza sativa L.) Lines with Durable Bacterial Blight Resistance through Phenotypic and Molecular Approaches

Bacterial leaf blight, caused by Xanthomonas oryzae pv. oryzae, is an important disease of rice that can substantially reduce crop performance under favourable disease conditions. The present study was conducted to identify elite rice lines resistant to bacterial leaf blight using phenotypic evaluation supported by molecular marker analysis. Thirty elite rice lines, together with the resistant check Improved Samba Mahsuri and the susceptible check TN-1, were evaluated under field conditions at the Regional Agricultural Research Station, Warangal, during Kharif, 2025. Artificial inoculation was performed using the leaf-clipping method, and disease reaction was recorded 15 days after inoculation according to the IRRI Standard Evaluation System. Molecular screening was performed using the pTa248 marker linked to the Xa21 resistance gene and the xa13 promoter marker linked to the xa13 resistance gene. Phenotypic screening showed that three lines, WG-GP-375, WG-GP-377 and WG-GP-378, exhibited a highly resistant reaction, while WG-GP-376 showed a resistant reaction. Eight lines were moderately susceptible, fifteen were susceptible and three were highly susceptible. Molecular analysis detected the Xa21 resistance allele in all four phenotypically resistant lines, whereas the xa13 resistance allele was detected in WG-GP-375, WG-GP-377 and WG-GP-378. The combined phenotypic and molecular assessment identified WG-GP-375, WG-GP-376, WG-GP-377 and WG-GP-378 as useful sources of bacterial leaf blight resistance. These lines may be considered for further validation and use in rice breeding programmes aimed at improving resistance to bacterial leaf blight.

A. Mahveen, A. Srijan, G. Seshu et al. · 0 citations
Open access Aug 2026

Marker-assisted Pyramiding of Bacterial Blight Resistance Genes into ‘Uma’, an Elite Red Rice Variety of Kerala

Background: Uma is a high-yielding, popular red-kernelled rice variety of Kerala; however, the occurrence of BB disease often causes severe yield reductions in this cultivar. Host plant resistance based on multiple genes is the most effective measure to impart durable resistance. Hence, efforts were undertaken to introgress the resistance genes, xa 5, xa13 and Xa21, from a BB-resistant variety, ISM, into Uma, using the MABB approach. Methods: Foreground selection was carried out using markers RG 556 and xa5 SR for xa5, RG136 and xa13 promoter for xa13 and pTA248 for Xa21 genes, respectively. The identified R-gene-pyramided plant was subjected to background selection using rice microsatellite markers for recurrent parent genome recovery. The phenotypic evaluation for BB resistance was carried out using the leaf-clipping method following the IRRI standard evaluation system, SES. Result: Molecular analysis of the recurrent parent Uma revealed the endogenous presence of R gene xa 5. The evaluation of BC2F1 lines identified a single plant pyramided with three resistance genes, with xa13 and Xa21 in the heterozygous condition, exhibiting a recurrent parent genome recovery of 70.45% and kernel characteristics similar to those of the Uma. Concurrently, BC1F2 lines generated from the cross were phenotypically screened for BB resistance, also identifying resistance to moderate resistance lines to the BB pathogen. Further advancement of these backcross generations was proposed to isolate gene pyramids homozygous for the resistance genes, with near-complete recurrent parent genome recovery.

Bhartiya Krishi, Anusandhan Patrika, L. Megha et al. · 0 citations
Open access Aug 2026

Characterisation of advanced breeding lines for bacterial leaf blight resistance by morpho-molecular screening in rice (Oryza sativa L.)

Sixty advanced breeding lines of rice were evaluated for resistance to bacterial leaf blight (BLB) both phenotypically and genotypically at Regional Agricultural Research Station (RARS), Maruteru, Andhra Pradesh, India during kharif, 2023. Phenotypic screening was performed following the International Rice Research Institute (IRRI), standard evaluation system (SES) scale. Among the sixty entries, seven genotypes, 251-3-3-2, MS-1, NLR-163, NLR-164, NLR-945, CM-469 and BM-587, exhibited a highly resistant (HR) reaction with a score of 1, comparable to the resistant check RP Bio-226. Twenty-two lines expressed BLB severity of 13–25 % (score 5) and were categorised as moderately resistant (MR). Molecular profiling using gene-specific simple sequence repeats (SSR) markers revealed significant variation in resistance genedistribution. The presence of xa5, xa13, Xa21, Xa4 and Xa10 was detected in 9, 4, 23, 44 and 20 lines respectively. Two-gene combinations were identified in 20 genotypes, whereas 11 genotypes possessed three-gene combinations, highlighting the effectiveness of gene stacking for broad-spectrum BLB resistance. Notably, lines 251-3-3-2, MS-1, NLR-164, NLR-945 and BM-587 exhibited congruence between phenotypic resistance (score 1) and the presence of multiple resistance genes, indicating their potential as elite donors for BLB resistance introgression. Yield performance coupled with gene pyramiding further strengthened the value of several genotypes. The genotypes VP-R-157 (Xa4+xa13) recorded 22.3 g/plant, BM-588 (xa5+Xa21) yielded 21.2 g/plant, while CM-467 (Xa4+xa5+Xa10+Xa21) produced 25.1 g/plant. The genotypes CM-470, CM-446 and CM-449 yielded 26.3 g, 21.0 g and 21.5 g/plant respectively, each carrying the Xa4+xa5 gene combination. These genotypes hold substantial promise for direct varietal release or utilisation in hybridisation programs aimed at developing high-yielding, BLB-resistant rice cultivars.

M. Jahnavi, Y. Satish, R. M. Ramabhadra et al. · 0 citations
Open access Jul 2026

QTL mapping for leaf rust resistance in bread wheat using PBW343/W8627 RIL population

Introduction Leaf rust, caused by Puccinia triticina, inflicts 10-50% yield losses in bread wheat, with newly emerging virulent pathotypes overcoming major Lr genes and rendering the cultivars susceptible. The identification of genetic loci conferring resistance to wheat leaf rust, coupled with the development of molecular markers and the incorporation of resistant alleles into breeding programs, represents the most sustainable and cost-effective strategy for disease management. Methods The present study, employed a recombinant inbred line population derived from (PBW343/W8627) was utilized to map QTLs for leaf rust resistance at seedling and adult plant stages. The RIL population along with its parents was evaluated at seedling and adult plant stages against most prevalent and virulent pathotypes at seedling and adult plant stages for the two crop seasons (2021-22 and 2022-23). Result Analysis of variance revealed significant differences among the RILs across years. For QTL mapping, genotyping was conducted using 3.9K DArT SNPs leading to the identification of two QTLs: QLr.iiwbr.2B.1 (2B) explaining phenotypic variance of 13.26% with a LOD score 8 and QLr.iiwbr.5B.1 (5B) explaining 14.91% with LOD score 3.91 for all stage resistance (ASR) as well as one QTL for adult plant resistance (APR), QLr.iiwbr.6B.1 (PVE 14.21%). Further, in silico analysis revealed a putative candidate gene encoding for Annexin (TraesCS5B02G201700) which plays an important role in disease resistance in wheat. Discussion The study identified new QTLs associated with leaf rust resistance, providing valuable sources to accelerate the development of durable rust resistant sources. Further, characterization of these QTLs will strengthen their utility in rust resistance breeding.

K. Vindhya, Renu Sharma, Satish Kumar et al. · 0 citations
Open access Aug 2026

Marker-Assisted Development of Rice Line G163 Combining Pi2-Mediated Blast Resistance, Xa7-Mediated Bacterial Blight Resistance, and Favorable Grain Quality

Rice blast and bacterial blight are two major diseases that threaten rice production worldwide. Developing rice cultivars with both disease resistance and desirable grain quality is an important objective in modern rice breeding. In this study, R1179 carrying Pi2, Wxb and Alkb was crossed with IRBB7 carrying Xa7, Wxb and Alkb. Marker-assisted selection (MAS) was applied to an F2 population of 1123 plants, and a line, G163, combining Pi2, Xa7, Wxb and Alkb, was developed. Disease resistance evaluation showed that G163 retained the blast resistance conferred by Pi2 and the bacterial blight resistance conferred by Xa7, exhibiting resistance to the tested isolates of both pathogens. Grain quality assessment indicated that G163 possessed favorable milling, appearance and eating quality traits. Rapid Visco Analyzer (RVA) profiling further indicated desirable starch pasting properties. In conclusion, the rice line G163 carrying Pi2, Xa7, Wxb and Alkb was successfully developed through MAS. The results provide a useful germplasm resource for breeding rice cultivars with combined disease resistance and desirable grain quality.

Ruomin Wu, Zhiyin Zhou, Jiayang Li et al. · 0 citations