Selecting a set of wild barley introgression lines and verification of QTL effects for resistance to powdery mildew and leaf rust

Abstract

A set of 59 spring barley introgression lines (ILs) was developed from the advanced backcross population S42. The ILs were generated by three rounds of backcrossing, two to four subsequent selfings, and, in parallel, marker-assisted selection. Each line includes a single marker-defined chromosomal segment of the wild barley accession ISR42-8 (Hordeum vulgare ssp. spontaneum), whereas the remaining part of the genome is derived from the elite barley cultivar Scarlett (H. vulgare ssp. vulgare). Based on a map containing 98 SSR markers, the IL set covers so far 86.6% (1041.5 cM) of the donor genome. Each single line contains an average exotic introgression of 39.2 cM, representing 3.2% of the exotic genome. The utility of the developed IL set is illustrated by verification of QTLs controlling resistance to powdery mildew (Blumeria graminis f. sp. hordei L.) and leaf rust (Puccinia hordei L.) which were previously identified in the advanced backcross population S42. Altogether 57.1 and 75.0% of QTLs conferring resistance to powdery mildew and leaf rust, respectively, were verified by ILs. The strongest favorable effects were mapped to regions 1H, 0-85 cM and 4H, 125-170 cM, where susceptibility to powdery mildew and leaf rust was decreased by 66.1 and 34.7%, respectively, compared to the recurrent parent. In addition, three and one new QTLs were localized, respectively. A co-localization of two favorable QTLs was identified for line S42IL-138, which holds an introgressed segment in region 7H, 166-181. Here, a reduction effect was revealed for powdery mildew as well as for leaf rust severity. This line might be a valuable resource for transferring new resistance alleles into elite cultivars. In future, we aim to cover the complete exotic genome by selecting additional ILs. We intend to conduct further phenotype studies with the IL set in regard to the trait complexes agronomic performance, malting quality, biotic stress, and abiotic stress.

An Extended Genetic Linkage Map for Watermelon Based on a Testcross and a BC<sub>2</sub>F<sub>2</sub> Population

“…The other 40 linkage groups were relatively small (each contains 2 -6 markers, covering a genetic distance of 0 -59 cM). The prevalence of small linkage groups here may reflect the possible introgression of chromosomal segments from PI 494817 into the genomic background of Crimson Sweet, as was shown in other studies using BC 2 F 2 or BC 3 F 2 populations fo the development of introgression lines [25,31,38]. r (Figure 2).…”

“…r (Figure 2). On the other hand, linkage groups 5,8,11,13,14,15,16,18,19,27,29,30,32,36,38,39,42,43,47, and 48 contain markers that represent the recurrent parent (Crimson Sweet) only (Figure 2). Linkage groups 1, 6, and 44 contain markers from both the donor and recurrent parent.…”

“…This BC 2 F 2 population should also prove useful for identifying and incorporating resistance genes that exist in wild watermelon [15,16] into cultivated watermelon. Plant breeding programs for different crop plants have been using introgression lines for incorporating resistance genes from wild progenitors into cultivated types [38].…”

QTL analysis in Barley Across Environments in Egypt

“…The cultivar Scarlett was used as the recurrent parent whereas ISR42-8 was utilized as the donor. More details about development of this population and proportion of donor genome are given in von Korff et al (2004) and Schmalenbach et al (2008). For comparison with barley local cultivars, four commercial cultivars of barley, i.e.…”

Power and false-positive rate in QTL detection with near-isogenic line libraries

“…These segments cover the entire genome of a donor line, and were introgressed into the genetic background of a recipient line by marker-assisted backcrossing. NIL libraries were suggested to detect quantitative trait loci (QTLs) in tomato (Lycopersicum esculentum, Eshed and Zamir, 1995) and were subsequently developed in Arabidopsis (Keurentjes et al, 2007;Törjek et al, 2008) and in a wide range of crops such as rice (Oryza sativa L., Lin et al, 1998), barley (Hordeum vulgare L., Matus et al, 2003;Schmalenbach et al, 2008), wheat (Triticum aestivum L., Liu et al, 2006), maize (Zea mays L., Ribaut and Ragot, 2007;Szalma et al, 2007) and rye (Secale cereale L., Falke et al, 2009b).…”