Abstract
Peanut is an important crop, economically and nutritiously, but high production cost is a serious challenge to peanut farmers as exemplified by chemical spray to control foliar diseases such as leaf spots and thrips, the vectors of tomato spotted wilt virus (TSWV). The objective of this research was to map the quantitative trait loci (QTLs) for resistance to leaf spots and TSWV in one recombinant inbred line (RIL) mapping population of “Tifrunner × GT-C20” for identification of linked markers for marker-assisted breeding. Here, we report the improved genetic linkage map with 418 marker loci with a marker density of 5.3 cM/loci and QTLs associated with multi-year (2010–2013) field phenotypes of foliar disease traits, including early leaf spot (ELS), late leaf spot (LLS), and TSWV. A total of 42 QTLs were identified with phenotypic variation explained (PVE) from 6.36 to 15.6%. There were nine QTLs for resistance to ELS, 22 QTLs for LLS, and 11 QTLs for TSWV, including six, five, and one major QTLs with PVE higher than 10% for resistance to each disease, respectively. Of the total 42 QTLs, 34 were mapped on the A sub-genome and eight mapped on the B sub-genome suggesting that the A sub-genome harbors more resistance genes than the B sub-genome. This genetic linkage map was also compared with two diploid peanut physical maps, and the overall co-linearity was 48.4% with an average co-linearity of 51.7% for the A sub-genome and 46.4% for the B sub-genome. The identified QTLs associated markers and potential candidate genes will be studied further for possible application in molecular breeding in peanut genetic improvement for disease resistance.
Highlights
Peanut (Arachis hypogaea L.) is an economically-important legume, and a major source of protein (25–28%) and vegetable oil (43–55%) for human nutrition
45 polymorphic markers were identified and 40 marker loci were successfully integrated into the existing genetic map (Qin et al, 2012; Pandey et al, 2014), along with the extensive phenotypic data in the field for disease resistances, this study reports the improved genetic map and the identification of QTLs linked to the resistance to early leaf spot (ELS), late leaf spot (LLS), and tomato spotted wilt virus (TSWV)
The early planted trials of April were mainly used for the spotted wilt rating in order to increase TSWV pressure, and the late planting was to reduce the TSWV interference with leaf spot rating but both plantings were used for leaf spots (ELS and LLS) evaluation in order to have optimized disease ratings (Li et al, 2012)
Summary
Peanut (Arachis hypogaea L.) is an economically-important legume, and a major source of protein (25–28%) and vegetable oil (43–55%) for human nutrition. Two thirds of peanut production is crushed for oil, and one third is consumed. QTLs for Peanut Leaf Spots and TSWV as food. High production cost is a challenge to peanut growers because of chemical spray to control diseases. Epidemics of leaf spot diseases can cause complete defoliation, resulting in significant yield losses. Control of leaf spot in the U.S depends on scheduled applications of fungicide (Culbreath et al, 2002). In the U.S, tomato spotted wilt virus (TSWV) has been an important factor of concern for breeders and farmers, and the control methods are limited (Culbreath et al, 2003; Culbreath and Srinivasan, 2011). TSWV is primarily transmitted by thrips, Frankliniella fusca (tobacco thrips), and F. occidentalis (western flower thrips) in the U.S From 1996 to 2006, TSWV disease alone caused the annual losses of $12.3 million (Riley et al, 2011)
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