Quantitative Trait Loci for Partial Resistance to Phytophthora sojae in Soybean

Abstract

Partial resistance to Phytophthora sojae Kauffmann and Gerdemann in soybean [Glycine max (L.) Merr.] is expressed as a reduced level of root rot and is effective against all populations of the pathogen. The objective of this study was to identify simple sequence repeat (SSR) markers associated with putative quantitative trait loci (QTLs) for partial resistance to P. sojae in the soybean ‘Conrad’. Three recombinant inbred soybean populations, Conrad × ‘Sloan’, Conrad × ‘Harosoy’, and Conrad × ‘Williams’, were evaluated for root lesion growth rate in growth chamber experiments following inoculation with P. sojae and with SSR markers to identify putative QTLs. The three populations segregated for root lesion growth rate after root inoculations. Two putative QTLs donated by Conrad were identified in all three populations and were positioned on soybean molecular linkage groups (MLGs) F and D1b+W. The QTL on MLG F explained 32.4, 35.0, and 21.4% of the genotypic variation for Conrad × Sloan, Conrad × Harosoy, and Conrad × Williams populations, respectively. The QTL on MLG D1b+W explained 10.6, 15.9, and 20.7% of the genotypic variation for the same three populations, respectively. The QTL on MLG F appears to be of more value based on the percentage of genotypic variation explained. Because the results indicate that QTLs for partial resistance to P. sojae map to different regions in soybean compared with the known Rps genes poses a challenge to soybean breeders. Marker‐assisted selection may expedite the process of combining both Rps genes with partial resistance into high‐yielding cultivars.

High‐Density Mapping of Resistance QTL Toward Phytophthora sojae, Pythium irregulare, and Fusarium graminearum in the Same Soybean Population

“…A population of 316 F 9:11 RILs was phenotyped for resistance to P. sojae by means of the tray assay as described previously (Burnham et al, 2003;Lee et al, 2013a,b;Wang et al, 2010Wang et al, , 2012a. In brief, plants were grown in vermiculite (Perlite Vermiculite Packing Industries, Inc.) in the greenhouse for 7 d, and the roots were washed in tap water to remove vermiculite.…”

“…The soybean cultivar 'Conrad' (Fehr et al, 1989) has been identified as a source of resistance to P. sojae and F. graminearum (Burnham et al, 2003;Li et al, 2010;Ellis et al, 2012;Wang et al, 2010Wang et al, , 2012a, while the cultivar 'Sloan' (Bahrenfus and Fehr, 1980) is moderately to highly susceptible to these same pathogens (Ellis et al, 2012;Wang et al, 2010Wang et al, , 2012a. Both cultivars have similar levels of moderate susceptibility to Py.…”

“…(Acharya et al, 2015;Burnham et al, 2003;Ellis et al, 2012;Stroup, 1989;Wang et al, 2010Wang et al, , 2012aWang et al, , 2012b. Class was treated as fixed, all other effects were treated as random.…”

Resistance to Pythium Seedling Disease in Soybean

“…glycinea) and two viral resistance alleles, Rsv1 (resistance to Soybean mosaic virus) and Rpv1 (resistance to Peanut mottle virus) (Ashfield et al, 1998;Ashfield et al, 2004;Gore, 2000;Hayes et al, 2004;Koning et al, 2002;Schmittehener, 1999). A QTL for partial resistance to P. sojae was reported on MLG F between marker Satt252 and Satt423 (Burnham et al, 2003b) and QTL's conferring resistance to Meloidogyne javanica, M. arenaria, Heterodera glycines, and soybean sudden death syndrome (SDS) have been mapped on the MLG F (Concibido et al, 1994;Hnetkovsky et al, 1996;Tamulonis, et al, 1997a;Tamulonis et al, 1997b;Webb et al, 1995). Nutrient availability is a limiting factor for microbial growth and activity in agricultural soils, as a result plant pathogenic fungi and oomycetes propagules survive in soils in a state of exogenous dormancy or fungistasis (Lockwood, 1977).…”

Genetic Improvement: Molecular-Based Strategies

“…Crosses between more diverse parents resulted in derived lines with greater values for grain yield (Table 1) and grain quality ( The SSR markers linked to the major QTL will be useful for marker-assisted selection in soybean-breeding programs (Funatsuki et al, 2005;Panthee et al, 2006). A set of SSR markers have been subjected to continuous development and utilization for high throughput molecular mapping in soybean (Akkaya et al, 1992(Akkaya et al, , 1995Narvel et al, 2000;Burnham et al, 2003;Shultz et al, 2007).…”