Integrating genotypic and phenotypic approaches for blast resistance selection in rice (Oryza sativa L.) segregating populations through marker-assisted selection

Exploring the Diversity of Blast Resistance Genes in Rice Lines Using PCR-Based Functional STS Markers

Rice blast, caused by Pyricularia oryzae (syn. Magnaporthe oryzae), remains one of the most destructive diseases of rice worldwide. Developing resistant varieties is a sustainable strategy for disease management, and information on the diversity of blast resistance genes is important for selecting breeding parents. This study evaluated the effectiveness of functional sequence-tagged site (STS) markers for resolving genetic diversity among advanced rice lines derived from multiple-cross populations. A total of 104 genotypes, comprising 100 advanced lines and four parental varieties (Ciherang, Inpari 13, Inpari 10, and Situ Bagendit), were analyzed using eight gene-specific STS markers associated with four blast resistance genes (Pii, Pia, Pikp, and Pita). Polymorphism information content (PIC) values ranged from 0.80 to 0.96, with a mean of 0.89. UPGMA cluster analysis separated the genotypes into two major groups at a similarity coefficient of 0.90, although most lines occurred in one group and lines with the same parental background were distributed among different subgroups. Observed heterozygosity was low (Ho = 0.09), indicating limited resolution for distinguishing closely related lines despite the high PIC values. Functional STS markers were informative for detecting allelic variation but were insufficient for resolving fine-scale relationships within this genetically narrow breeding population. Combining marker analysis with phenotypic evaluation and higher-resolution markers is therefore recommended to improve selection for blast resistance.

Linkage Mapping Study Reveals Conservative QTL and Candidate Genes for Fusarium Ear Rot Resistance in Maize

A recombinant inbred line (RIL) population consisting of 257 progenies was developed by crossing the resistant line BT with the susceptible line Xi502, suggesting their potential association with FER resistance.

Genetics and Resistance / Génétique et Résistance Genetic mapping and marker development for the leaf rust resistance gene Lr30 in wheat ( Triticum aestivum L.)

This study generated the first linkage map of Lr30, a gene that confers resistance against leaf rust caused by Puccinia triticina Eriks, and developed Kompetitive allele-specific PCR (KASP) markers linked to Lr30 for marker-assisted breeding.

Integrated Analysis of Genetic Diversity, Trait Association and Fertility Restorer Genes (Rf3 and Rf4) in Rice

Marker-assisted backcross breeding to develop wheat lines with stable yellow rust resistance without yield penalties

Wheat production faces severe yield threats globally and regionally in India from rust diseases caused by Puccinia species. Genetic resistance breeding is the most sustainable approach to mitigate these losses, but traditional phenotypic selection is often constrained by environmental fluctuations and rapid pathogen evolution. Here we utilized marker-assisted backcross breeding (MABB) to introgress broad-spectrum yellow rust resistance genes, Yr10 and Yr15 , from the donor genetic stock PBW703 into the elite, high-yielding wheat cultivar DBW88 to develop two high-yielding rust-resistant genotypes DBW476 and DBW477. Foreground selection was executed using gene-linked molecular markers PSP3000 ( Yr10 ) and Xbarc8 ( Yr15 ). Background selection with 107 polymorphic simple sequence repeat (SSR) markers accelerated recurrent parent genome recovery up to 95% within just two backcross generations, significantly outperforming conventional breeding timelines. Seedling resistance tests and adult plant resistance evaluations confirmed that the introgressed lines exhibited a high degree of immune response and comprehensive resistance against virulent Puccinia striiformis pathotypes, including 238S119 and 110S119. Multi-year agronomic testing across multiple environments demonstrated that the improved near-isogenic lines achieved equal or superior grain yield performance compared to their recurrent parents and commercial checks. These findings indicate successful gene introgression without any associated linkage drag or yield penalties. These advanced, stable lines were nominated for multi-location varietal trials, presenting a strategically superior asset for sustainable rust management and food security in the rust-prone environments of India.

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.