Postulation of resistance genes and assessment of adult plant response variation for stripe rust in three international wheat nurseries

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is an important disease of wheat in cooler and humid geographic regions. It can cause significant yield losses. Three international nurseries, namely, 1^st Australian Special Nursery (ASN), 22^nd Semi-Arid Wheat Screening Nursery (SAWSN) and 12^th High Temperature Wheat Yield Trial (HTWYT), were evaluated for seedling and adult plant response variation for stripe rust. A low proportion of these nurseries displayed stripe rust resistance in the seedling stage.Fifty one percent of 1^st ASN, 54% 22^nd SAWSN and 17% 12^th HTWYT entries did not carry any seedling resistance genes. High level of APR to stripe rust was expressed in the field in all three nurseries. Stripe rust resistance genes Yr6,Yr7,Yr9, Yr17 and Yr27 were postulated either singly or in combinations across the three nurseries. Some entries carried these genes in combination with uncharacterised resistance. Based on Lr34 and Sr2 linked markers, Yr18 and Yr30 are inferred to be present in a high proportion of entries in all three nurseries. Due to the lack of robust marker, we were unable to postulate Yr29, this gene is however expected to be present in Pavon 76 derivatives. Results of this study can be used for strategic deployment of stripe rust resistance in new wheat cultivars.