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

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.

Molecular genetic analysis of potato genotypes for late blight resistance

Increasing crop yields and enhancing their adaptation to changing growing conditions are among the key strategies for ensuring food security. Potato is one of the most important food crops worldwide and is cultivated on all continents. Plant breeders play a crucial role in ensuring sustainable potato production by developing new resistant varieties with increased yield per hectare. Since the 1990s, genetics has played an increasingly important role in plant breeding through the introduction of DNA markers as indirect selection tools and for the assessment of genetic diversity. Today, genomics-based plant breeding approaches, such as marker-assisted selection (MAS) and genomic selection (GS), accelerate the breeding process for many major crops. The aim of this study was to identify genes conferring late blight resistance in 30 promising potato hybrids using DNA markers. Laboratory analyses for late blight resistance were conducted at the Laboratory of Molecular Genetic Research of Agricultural Plants at the Vladikavkaz Scientific Center of the Russian Academy of Sciences. The breeding material was preliminarily evaluated under field conditions in accordance with the recommendations for potato breeding programs. Genomic DNA was extracted from potato leaves during the flowering period using the CTAB method. For molecular genetic analysis of late blight resistance, the following R-gene molecular markers were used: R1–1250, R3a-1380, and R3b-378. The molecular genetic analysis revealed the presence of all three markers R1–1250, R3a-1380, and R3b-378. They were identified in five different potato hybrids. These hybrids included: 3375–1 (Tiras × Breeze), 3403–2 (Arizona × Fritella), 3341–2 (Innovator × Mirage), 3352–1 (Kolette × Mirage), and 3352–4 (Kolette × Mirage). The presence of all three genes indicates a high degree of late blight resistance. Thus, the identification of potato genotypes using molecular markers facilitates the acceleration of the breeding process for developming new resistant potato varieties.

Construction and evaluation of 9311 resistance gene pyramiding lines with combined resistance to brown planthopper and rice blast

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.

Genetics and Resistance / Génétique et Résistance High-confidence genomic regions associated with leaf stripe and spot blotch resistance in barley

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.