Mapping Quantitative Trait Loci for Partial Resistance to Phytophthora sojae in a Soybean Interspecific Cross

Abstract

Phytophthora root and stem rot of soybean, caused by Phytophthora sojae Kaufmann & Gerdemann, is a serious limitation to soybean [Glycine max (L.) Merr.] production in the USA. Partial resistance or field resistance to P. sojae in soybean is effective against multiple races of the pathogen and is a form of incomplete resistance. An interspecific recombinant inbred line (RIL) population consisting of 298 individuals derived from the cross of V71–370 by PI407162 was inoculated with the P. sojae isolate C2S1 using the slant board technique in three separate experiments (designated as 2005, 2006a, and 2006b). In each replication, seven day old seedlings from each RIL were inoculated and lesion lengths were recorded 7 d later to assess partial resistance with three replications for the 2005 and 2006a experiments and one replication for the 2006b screening. Interval mapping located a lesion length QTL on each of the molecular linkage groups (MLGs)–J (chrom. 16),‐I (chrom. 20) and–G (chrom. 18) in all three experiments. The lesion length QTL on MLG‐J accounted for 32, 42, and 22% of the phenotypic variation in the 2005, 2006a and 2006b experiments, respectively. Mapped QTL locations in the current study provide breeders with new sources of P. sojae resistance and suggest that new sources may be identified in soybean germplasm.

Genetic variants in root architecture-related genes in a Glycine soja accession, a potential resource to improve cultivated soybean

“…The population was first developed to map resistance genes for Phytophthora sojae in soybean [68,69] . However, in the seedling stage the parental lines also differ for various components of the root system architecture, which enabled us to map QTLs for various root traits in the present study.…”

Identification and validation of quantitative trait loci for seed yield, oil and protein contents in two recombinant inbred line populations of soybean

“…Single marker analysis (SMA), interval mapping (IM), and composite interval mapping (CIM) were performed. Based on permutation tests performed 1,000 times at α = 0.05 for experiment-wise Type I error and referring to the empirical threshold values widely used for QTL mapping (Bachlava et al 2009;Panthee et al 2006;Tucker et al 2010), a LOD value of 2.5 was set as the threshold for significance of a QTL. In a few cases, the QTLs with a LOD value above 2.0 (equivalently P = 0.002 and significant at P < 0.01 for ANOVA) were also declared significant to avoid missing of QTLs due to slightly lower significance (Cornelious et al 2005;Wang et al 2014;Yesudas et al 2013).…”

Pathogenic diversity of Phytophthora sojae and breeding strategies to develop Phytophthora-resistant soybeans

“…Several QTLs for partial resistance to P. sojae have been reported, and the molecular markers linked to the QTLs could be used for developing cultivars with partial resistance (Burnham et al 2003, Han et al 2008, Tucker et al 2010, Weng et al 2007). However, it is still difficult to integrate multiple QTLs at independent loci into a cultivar without some adverse effects.…”