QTL associated with horizontal resistance to soybean cyst nematode in Glycine soja PI464925B |
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Authors: | Shawn M J Winter Barry J Shelp Terry R Anderson Tom W Welacky Istvan Rajcan |
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Institution: | (1) Department of Plant Agriculture, University of Guelph, N1G 2W1 Guelph, ON, Canada;(2) Greenhouse and Processing Crop Research Center, Agriculture and Agri-Food Canada, N0R 1G0 Harrow, ON, Canada |
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Abstract: | Soybean cyst nematode (Heterodera glycines Ichinohe; SCN) is the primary disease responsible for yield loss of soybean Glycine max (L.) Merr.]. Resistant cultivars are an effective management tool; however, the sources currently available have common resistant
genes. Glycine soja Sieb. and Zucc., the wild ancestor of domesticated soybean, represents a diverse germplasm pool with known SCN resistance.
The objectives of this research were to: (1) determine the genetic variation and inheritance of SCN resistance in a G. max (‘S08-80’) × G. soja (PI464925B) F
4:5 recombinant inbred line (RIL) population; and (2) identify and evaluate quantitative trait loci (QTL) associated with SCN
resistance. Transgressive segregation for resistance was observed, although neither parent was resistant to the Chatham and
Ruthven SCN isolates. Broad sense heritability was 0.81 for the Ruthven and 0.91 for the Chatham isolate. Root dry weight
was a significant covariate that influenced cyst counts. One RIL female index (FI) = 5.2 ± 1.11] was identified as resistant
to the Chatham isolate (FI < 10). Seventeen and three RILs infected with Chatham and Ruthven isolates, respectively, had mean
adjusted cyst counts of zero. Unique and novel QTL, which derived resistance from G. soja, were identified on linkage groups I, K, and O, and individually explained 8, 7 and 5% (LOD = 2.1–2.7) of the total phenotypic
variation, respectively. Significant epistatic interactions were found between pairs of SSR markers that individually may
or may not have been associated with SCN resistance, which explained between 10 and 15% of the total phenotypic variation.
Best-fit regression models explained 21 and 31% of the total phenotypic variation in the RIL population to the Chatham and
Ruthven isolates, respectively. The results of this study help to improve the understanding of the genetic control of SCN
resistance in soybean caused by minor genes resulting in horizontal resistance. The incorporation of the novel resistance
QTL from G. soja could increase the durability of SCN-resistance in soybean cultivars, especially if major gene resistance breaks down. |
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