Abstract
Barley stripe rust is caused by Puccinia striiformis f.sp. hordei, (Psh), occurs worldwide, and is a major disease in South Asia. The aim of this work was to identify and estimate effects of loci underlying quantitative resistance to rust at seedling and adult plant stages. HI-AM panel of 261 barley genotypes consisting of released cultivars from North and South America, Europe, Australia, advanced breeding lines, and local landraces from ICARDA barley program were screened at seedling and adult plant stages for resistance to Psh. Seedling resistance was evaluated with the five prevalent Psh races in India. Screening for the adult plant stage resistance was also performed in two different locations by inoculating with a mixture of the five races used for seedling screeing. The panel was genotyped using DaRT-Seq high-throughput genotyping platform. The genome-wide association mapping (GWAM) showed a total of 45 QTL located across the seven barley chromosomes for seedling resistance to the five races and 18 QTL for adult plant stage resistance. Common QTL for different races at seedling stage were found on all chromosomes except on chromosome 1H. Four common QTL associated with seedling and adult plant stage resistance were found on chromosomes 2, 5, and 6H. Moreover, one of the QTL located on the long arm of chromosome 5H showed stable effects across environments for adult plant stage resistance. Several QTL identified in this study were also reported before in bi-parental and association mapping populations studies validating current GWAM. However 15 new QTL were found at adult plant stage on all chromosomes except the 4H, explaining up to 36.79% of the variance. The promising QTL detected at both stages, once validated, can be used for MAS in Psh resistance breeding program globally.
Highlights
Barley (Hordeum vulgare L.) is one of the most important cereal crops in the word and especially in the dry areas where often is the only crop that can be grown under extreme drought conditions (Ceccarelli, 1994; Li et al, 2006)
Durgapura represents an optimal site for Psh due to climatic conditions that favors Psh development while Karnal is characterized by the occurrence of severe winters that may limit the development and sporulation of the rust for the secondary spread
We found that 13 out of 18 quantitative trait loci (QTL) detected at Adult-plant stage (APS) were not coincident with those detected at seedling resistance test (SRT), they can be considered QTL for Adult Plant Resistance (APR)
Summary
Barley (Hordeum vulgare L.) is one of the most important cereal crops in the word and especially in the dry areas where often is the only crop that can be grown under extreme drought conditions (Ceccarelli, 1994; Li et al, 2006). Rust pathogens have intrinsic characteristic like windaided migration, ability to increase population size and to mutate and acquire new virulence to resistance genes. Due to these characteristics quantitative resistance is preferable to qualitative resistance for long lasting cultivation of new resistant cultivars. With more than 70 Psh races identified (Hovmøller, 2002) a better understanding of the genetic control of quantitative resistance is of crucial importance and breeding would be more effective if based on extensive knowledge of the resistance genes/QTL (Gutiérrez et al, 2015). The current study was undertaken to identify QTL effective against Psh individual races at seedling stage and QTL for quantitative resistance in field globally and especially for South Asia where annual recurrence of stripe rust from the Himalayas is a big challenge
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