Identification of leaf rust resistance genes i n selected Argentinean bread wheat cultivars by gene postulation and molecular markers

Abstract

Leaf rust, caused by Puccinia triticina Eriks. is a common and widespread disease of bread wheat (Triticum aestivum L.), in Argentina. Host resistance is the most economical, effective and ecologically sustainable method of controlling the disease. Gene postulation helps to determine leaf rust resistance genes (Lr genes) that may be present in a large group of wheat germplasm. Additionally presence of Lr genes can be determined using associated molecular markers. The objective of this study was to identify Lr genes that condition leaf rust resistance in 66 wheat cultivars from Argentina. Twenty four differential lines with individual known leaf rust resistance genes were tested with 17 different pathotypes of leaf rust collected from Argentina. Leaf rust infection types produced on seedling plants of the 66 local cultivars were compared with the infection types produced by the same pathotypes on Lr differentials to postulate which seedling leaf rust genes were present. Presence of Lr9, Presence of Lr21, Lr25, Lr29, and Lr47 could not be determined with the seventeen pathotypes used in the study because all were avirulent to these genes. Eleven cultivars (16.7%) were resistant to all pathotypes used in the study and the remaining 55 (83.3%) showed virulent reaction against one or more local pathotypes. Cultivars with seedling resistance gene combinations including Lr16 or single genes Lr47 (detected with molecular marker), Lr19 and Lr41, showed high levels of resistance against all pathotypes or most of them. On the opposite side, cultivars with seedling resistance genes Lr1, Lr3a, Lr3a + Lr24, Lr10, Lr3a + Lr10, Lr3a + Lr10 + Lr24 showed the highest number of virulent reactions against local pathotypes. Occurrence of adult plant resistance genes Lr34, Lr35 and Lr37 in local germplasm was evaluated using specific molecular markers confirming presence of Lr34 and Lr37. Our data suggest that combinations including seedling resistance genes like Lr16, Lr47, Lr19, Lr41, Lr21, Lr25 and Lr29, with adult plant resistance genes like Lr34, SV2, Lr46 will probably provide durable and effective resistance to leaf rust in the region.

Genetic analysis of rust resistance genes in global wheat cultivars: an overview

“…The combined effects of the adult resistance genes Lr11, Lr12, Lr13, Lr22b, Lr35, and Lr37 have been reported in 55% of European wheat cultivars [18]. The combined effects of seedling resistance genes, such as Lr16, Lr47, Lr19, Lr41, Lr21, Lr25 and Lr29, with APR genes, such as Lr34, SV2, Lr46, might explain the highly durable and effective leaf rust control that has been achieved in Argentinean wheat cultivars [45]. The combination of Lr35 with seedling and/or other adultplant leaf rust resistance genes should facilitate more efficient breeding for durable resistance [155].…”

“…The Lr20 gene is very rare in Australian germplasm, American soft red winter wheat, and Argentinian germplasm [41,122]. The Lr1 gene has been most frequently recorded in Australian wheat cultivars, American hard red spring wheat, Mexican bread wheat, Chinese cultivars, and Indian and Pakistani wheat cultivars [122,179,[180][181][182], while this gene is rare in Argentinean germplasm [45]. The Lr10 is very common in international winter wheat nurseries, Indian and Pakistani wheat cultivars, Mexican bread wheat, and Brazilian and Argentinean wheat cultivars [44,45,[181][182][183].…”

“…The Lr1 gene has been most frequently recorded in Australian wheat cultivars, American hard red spring wheat, Mexican bread wheat, Chinese cultivars, and Indian and Pakistani wheat cultivars [122,179,[180][181][182], while this gene is rare in Argentinean germplasm [45]. The Lr10 is very common in international winter wheat nurseries, Indian and Pakistani wheat cultivars, Mexican bread wheat, and Brazilian and Argentinean wheat cultivars [44,45,[181][182][183]. Soft red winter wheat cultivars from the southeastern USA bearing the leaf rust resistance genes Lr9, Lr11, Lr18, Lr24 and Lr26 can be infected by selected races with virulence against these genes [184].…”

“…The Lr3, Lr3ka, Lr3bg, and Lr26 genes are most frequently found in Western European wheat cultivars [190]. The Lr26 is most commonly found in Argentinean germplasm [45], British cultivars [178] and Chinese wheat germplasm. Due to its durable resistance ability, Lr13 is the most widely distributed Lr gene in world wheat cultivars [26].…”

Recent Advances on Integrated Foliar Disease Management with Special Emphasis in Argentina Wheat Production

“…Genes Lr20, Lr21, Lr25, Lr29, Lr35 (adult plant resistance gene) and Lr51 were not detected in tested cultivars [49]. Resistance in most Argentinean cultivar and around the world is conditioned by one or a few genes.…”