Molecular Characterization of Diverse Wheat Genetic Resources for Resistance to Yellow Rust Pathogen (Puccinia striiformis)

Abstract

Yellow rust (YR) epidemics have affected wheat productivity worldwide. YR resistance (Yr) is eminent in wheat; however, it is continuously invaded by evolving YR pathogen Puccinia striiformis (Pst.). Understanding the Yr genes’ diversity among the available germplasm is paramount to developing YR-resistant cultivars. In this study, 14 wheat genotypes were screened for their relative resistance index (RRI) and Yr genes/QTL via linked microsatellite markers. RRI screening categorized the studied genotypes into susceptible (<5; 4.44 ± 0.75), moderate (5–7; 6.11 ± 0.64), and resistant (>7; 8.45 ± 0.25) bulks (p < 0.001). Genetic analysis using 19 polymorphic microsatellite markers revealed 256 alleles, which were divergent among the three resistance bulks. Markers Xbarc7 and Xgwm429 showed the highest allelic diversity in comparison to Xbarc181, Xwmc419, SCAR1400, and Xgwm130. Resistant bulk showed associated alleles at Yr18 gene-linked markers Xgwm295, cssfr6, and csLV34. Other RRI-associated alleles at markers Xbarc7 and Xbarc101 showed weak and moderate linkages, respectively, with the Yr5 gene; whereas, a moderate association was noted for the Yr15 gene-linked marker Xgwm11. Marker Xwe173 linked with the Yr26 gene showed associated alleles among the susceptible bulk. Cross combinations of the parental lines forming recombinant inbred lines (RILs) demonstrated net higher RRI implying favorable allelic recombination. These results support reports and field observations on novel Pst. races that triggered Yr26, Yr5, and Yr15 busts in recent past. This study further implies that pyramiding all stage resistance genes (Yr5, Yr10, Yr15, and Yr26) with adult plant resistance genes (Yr18 and Yr62) should provide sustained YR resistance. The associated alleles at Yr genes-linked markers provide a basis for marker-assisted YR resistance breeding in wheat.

Mechanism of Wheat's Drought Tolerance: A Review

“…Wheat production has to double by 2027. In 2013/14, Pakistan's wheat harvest contributed 4.44 percent to the country's gross domestic product (Saeed et al, 2022). Triticum wheat species are crucial to developing high-yielding cultivars and significantly contribute to human nourishment, even in water-limited settings (Tester & Langridge, 2010).…”

Application of Molecular Markers in Crop Improvement and Beyond

“…The pyramiding of the resistance allele is easier to achieve with the use of molecular markers, as shown in yellow rust resistance in wheat [9]. These authors grouped 14 genotypes of wheat into three groups, including susceptible, moderate, and resistant, based on the relative resistance index, screening these genotypes using 19 polymorphic SSR markers.…”

“…These authors grouped 14 genotypes of wheat into three groups, including susceptible, moderate, and resistant, based on the relative resistance index, screening these genotypes using 19 polymorphic SSR markers. They were able to identify resistant genes, including Yr5, Yr10, Yr15, and Yr26 (all-stage resistance genes); Yr18 and Yr62 (adult plant) resistance genes; and pyramids using molecular markers [9]. In a sexually propagated pathogen such as Puccinia stritiformis, the causal agent of leaf rust, it is essential to pyramid the available resistant alleles and explore new alleles to combat new types of pathogens.…”