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

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.

Evaluation of Local Rice Genotypes from Southwest Aceh for Resistance to Bacterial Leaf Blight (Xoo Strain VIII)

Local rice germplasm is a valuable genetic resource for developing bacterial leaf blight (BLB)-resistant and high-yielding rice cultivars. However, information on the resistance of Southwest Aceh local rice to Xanthomonas oryzae pv. oryzae (Xoo), particularly during the generative stage, remains limited. Previous studies have mainly focused on commercial cultivars or vegetative-stage screening, leaving the resistance potential of local germplasm at the reproductive stage largely unexplored. This study aimed to evaluate the resistance of local rice to BLB at the generative stage of plant growth. The research was conducted at Experimental Field, Teuku Umar University. West Aceh (4°08′33″ N; 96°11′54″ E). Fifteen local rice genotypes, together with resistant and susceptible control varieties, were evaluated following artificial inoculation with Xoo strain VIII. Disease resistance was assessed based on incubation period and lesion length, while agronomic performance was evaluated using key yield-related traits. Seven local genotypes Itam Tangke Lango, Jantong, Jempa Puteh, Manyam U, Pade Manggeng-1, Pade Manggeng-2, and Rangan Lango were classified as resistant based on lesion length. Among the evaluated genotypes, Sikleng exhibited superior agronomic performance, producing the highest number of productive tillers (27.50) and grains per panicle (317.73). The novelty of this study lies in evaluating Southwest Aceh local rice germplasm for bacterial leaf blight resistance at the generative stage using Xoo strain VIII while integrating disease resistance with yield-related agronomic traits. The identified resistant genotypes provide valuable donor parents for breeding BLB-resistant, high-yielding rice cultivars and contribute to sustainable rice production and regional food security.

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.

Identification of stripe rust resistance loci in Gansu wheat landraces using genome-wide association analysis

Evaluation of Disease Resistance in Wheat Genotypes for Organic Farming Under Kazakhstan Conditions

Kazakhstan possesses considerable potential for the development of organic agriculture. In organic production systems, the use of chemical plant protection products is restricted or completely excluded, making the cultivation of genetically resistant wheat lines to major fungal diseases one of the most effective approaches for maintaining stable grain production. The current study aimed to evaluate disease resistance in wheat genotypes by integrating phenotypic screening and marker-assisted selection and their validation under organic farming conditions. A total of 50 facultative and introgressive wheat lines were evaluated under an artificial infection background for resistance to yellow rust, leaf rust, stem rust, and common bunt. Molecular marker analysis was performed to identify resistance-associated alleles. Integrated phenotypic and molecular analyses enabled the identification of three promising genotypes, namely 1675-52, 1723-32, and 1716-24. They combined a high level of resistance to yellow rust and common bunt with the presence of resistance-associated alleles. These selected genotypes were subsequently validated under organic field conditions. The results demonstrated that these lines maintained stable resistance to yellow rust and common bunt and produced seed yield ranging from 5.45 to 5.94 t/ha, exceeding that of the standard cv. Almaly (4.88 t/ha). The obtained results confirm the effectiveness of integrating phenotypic screening with marker-assisted selection for identifying wheat genotypes with complex disease resistance. These genotypes represent promising prebreeding resources for organic agriculture, subject to validation across a wider range of environments.

Deciphering bacterial wilt resistance in eggplant: identification of elite lines, DNA marker validation and transcriptome profiling