AUTHOR=Randhawa Mandeep S. , Singh Ravi P. , Dreisigacker Susanne , Bhavani Sridhar , Huerta-Espino Julio , Rouse Matthew N. , Nirmala Jayaveeramuthu , Sandoval-Sanchez Maricarmen 

TITLE=Identification and Validation of a Common Stem Rust Resistance Locus in Two Bi-parental Populations

JOURNAL=Frontiers in Plant Science

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.01788

DOI=10.3389/fpls.2018.01788

ISSN=1664-462X

ABSTRACT=<p>Races belonging to Ug99 lineage of stem rust fungus <italic>Puccinia</italic><italic>graminis</italic> f. sp. <italic>tritici</italic> (<italic>Pgt</italic>) continue to pose a threat to wheat (<italic>Triticum</italic><italic>aestivum</italic> L.) production in various African countries. Growing resistant varieties is the most economical and environmentally friendly control measure. Recombinant inbred line (RIL) populations from the crosses of susceptible parent ‘Cacuke’ with the resistant parents ‘Huhwa’ and ‘Yaye’ were phenotyped for resistance at the seedling stage to <italic>Pgt</italic> race TTKSK (Ug99) and in adult plants in field trials at Njoro, Kenya for two seasons in 2016. Using the Affymetrix Axiom breeders SNP array, two stem rust resistance genes, temporarily designated as <italic>SrH</italic> and <italic>SrY</italic>, were identified and mapped on chromosome arm 2BL through selective genotyping and bulked segregant analysis (BSA), respectively. Kompetitive allele specific polymorphism (KASP) markers and simple sequence repeat (SSR) markers were used to saturate chromosome arm 2BL in both RIL populations. <italic>SrH</italic> mapped between markers <italic>cim109</italic> and <italic>cim114</italic> at a distance of 0.9 cM proximal, and <italic>cim117</italic> at 2.9 cM distal. <italic>SrY</italic> was flanked by markers <italic>cim109</italic> and <italic>cim116</italic> at 0.8 cM proximal, and <italic>IWB45932</italic> at 1.9 cM distal. Two Ug99-effective stem rust resistance genes derived from bread wheat, <italic>Sr9h</italic> and <italic>Sr28</italic>, have been reported on chromosome arm 2BL. Infection types and map position in Huhwa and Yaye indicated that <italic>Sr28</italic> was absent in both the parents. However, susceptible reactions produced by resistant lines from both populations against <italic>Sr9h</italic>-virulent race TTKSF+ confirmed the presence of a common resistance locus <italic>Sr9h</italic> in both lines. Test of allelism is required to establish genetic relationships between genes identified in present study and <italic>Sr9h</italic>. Marker <italic>cim117</italic> linked to <italic>SrH</italic> was genotyped on set of wheat lines with Huhwa in the pedigree and is advised to be used for marker assisted selection for this gene, however, a combination of phenotypic and genotypic assays is desirable for both genes especially for selection of <italic>Sr9h</italic> in breeding programs.</p>