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Open access Aug 2026

A successful stacking of multiple biotic stress resistance in rice facilitated by genes and precision breeding tools

Genetic improvement of rice for biotic stress is a major and continuous breeding objective owing to changing pest and disease scenarios. In response to climate change, an outbreak of new pathotypes and biotypes results in huge yield loss which directly impacts the economic stability and food security. The development of varieties with multiple resistance genes for a particular disease is the most effective approach to the combating mechanism against evolving pathogens and insects. Multiple resistance genes against blast (Pi54), bacterial leaf blight (xa5, xa13, Xa21), and brown plant hopper (Bph17, Bph3, bph2) were pyramided through marker-assisted forward breeding by attempting multiple crosses involving six parental lines. The F4 lines were screened and the resistant lines were further reconfirmed at the F5 stage through precise phenotyping and also by genotyping with trait-specific markers. Finally, the selected lines were evaluated for the agronomic performance. Four lines were selected from the population which carrying seven resistance genes against BL, BB, BPH with superior agronomic performance. Another line, x21302-239, harboring all the resistant genes and showing a resistant response in screening experiments for all three stresses, with marginal agronomic performance (single-plant yield: 33 g), can be utilized as a desirable donor to develop elite rice cultivars with multiple biotic stress resistance. Homozygous genetic background is more favorable for epidemic outbreak in a short period of time in comparison with the population of multiple genetic background. Since this complex genetic background disturbs the infectious cycle of the pathogen. So that a variety or a hybrid which developed from multiple parental lines are notable for their durable resistance than the monogenic resistance variety.

M. Sriram, K. Amudha, Swaminathan Manonmani et al. · 0 citations
Open access Sep 2026

Agronomic Performance of Aromatic Rice (BC4F1) Derived from Inpari 33 × Merah Wangi Crosses

Background: Aromatic rice quality is primarily determined by loss-of-function mutations in the BADH2 gene, which lead to the accumulation of 2-acetyl-1-pyrroline (2AP). This study aimed to introgress the BADH2 aromatic allele from Merah Wangi into the high-yielding variety Inpari 33 and to evaluate the agronomic performance of the resulting BC4F1 population. Methods: A breeding program consisting of four backcross cycles was conducted using Inpari 33 as the recurrent parent and Merah Wangi as the donor parent. Marker Marker-assisted breeding using Bradbury markers was applied to identify plants carrying the BADH2 mutation. Agronomic traits, including heading date, plant height, panicle length, tillering capacity, yield components and grain quality were assessed to characterize phenotypic performance. Result: Twenty heterozygous aromatic plants were identified, confirming successful introgression of the BADH2 mutant allele. The BC4F1 population showed uniform heading date, intermediate plant height and increased panicle length relative to Inpari 33. The productive tillers, filled grains per panicle and grain yield per plant demonstrated improved performance, even though variability persisted in grain filling and 1000-grain weight. These findings indicate that the integration of the BADH2 allele and the overall agronomic response validate the effectiveness of Marker Assisted Breeding combined with repeated backcrossing for developing improved aromatic rice lines, while further selection is still required to stabilize key traits.

Unknown authors · 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 Aug 2026

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.

A. Prihaningsih, S. Yuriyah, Joko Prasetyo et al. · 0 citations
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 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, Zhi-Yin Zhou, Jiayang Li et al. · 0 citations

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