Development and Evaluation of Glycine max Germplasm Lines with Quantitative Resistance to Sclerotinia sclerotiorum

Abstract

Sclerotinia sclerotiorum, the causal agent of Sclerotinia stem rot, is a devastating fungal pathogen of soybean that can cause significant yield losses to growers when environmental conditions are favorable for the disease. The development of resistant varieties has proven difficult. However, poor resistance in commercial cultivars can be improved through additional breeding efforts and understanding the genetic basis of resistance. The objective of this project was to develop soybean germplasm lines that have a high level of Sclerotinia stem rot resistance to be used directly as cultivars or in breeding programs as a source of improved Sclerotinia stem rot resistance. Sclerotinia stem rot-resistant soybean germplasm was developed by crossing two sources of resistance, W04-1002 and AxN-1-55, with lines exhibiting resistance to Heterodera glycines and Cadophora gregata in addition to favorable agronomic traits. Following greenhouse evaluations of 1,076 inbred lines derived from these crosses, 31 lines were evaluated for resistance in field tests during the 2014 field season. Subsequently, 11 Sclerotinia stem rot resistant breeding lines were moved forward for field evaluation in 2015, and seven elite breeding lines were selected and evaluated in the 2016 field season. To better understand resistance mechanisms, a marker analysis was conducted to identify quantitative trait loci linked to resistance. Thirteen markers associated with Sclerotinia stem rot resistance were identified on chromosomes 15, 16, 17, 18, and 19. Our markers confirm previously reported chromosomal regions associated with Sclerotinia stem rot resistance as well as a novel region of chromosome 16. The seven elite germplasm lines were also re-evaluated within a greenhouse setting using a cut petiole technique with multiple S. sclerotiorum isolates to test the durability of physiological resistance of the lines in a controlled environment. This work presents a novel and comprehensive classical breeding method for selecting lines with physiological resistance to Sclerotinia stem rot and a range of agronomic traits. In these studies, we identify four germplasm lines; 91–38, 51–23, SSR51–70, and 52–82B exhibiting a high level of Sclerotinia stem rot resistance combined with desirable agronomic traits, including high protein and oil contents. The germplasm identified in this study will serve as a valuable source of physiological resistance to Sclerotinia stem rot that could be improved through further breeding to generate high-yielding commercial soybean cultivars.

Resistance against Sclerotinia sclerotiorum in soybean involves a reprogramming of the phenylpropanoid pathway and up‐regulation of antifungal activity targeting ergosterol biosynthesis

“…Disease development in the resistant (91-145) and susceptible (91-44) soybean lines Two recombinant inbred lines (RIL) of soybean showing a differential response to S. sclerotiorum were chosen for this study. The resistant and susceptible selections were classified based on our previous germplasm selection study (McCaghey et al, 2017). Both the resistant 91-145 (R) and the susceptible 91-44 (S) lines were developed utilizing the SSR resistant parental line W04-1002 (P1) and LN89-5717 (PI 5745542), an SSRsusceptible parental line having other desirable pathogen resistance traits (McCaghey et al, 2017).…”

“…The resistant and susceptible selections were classified based on our previous germplasm selection study (McCaghey et al, 2017). Both the resistant 91-145 (R) and the susceptible 91-44 (S) lines were developed utilizing the SSR resistant parental line W04-1002 (P1) and LN89-5717 (PI 5745542), an SSRsusceptible parental line having other desirable pathogen resistance traits (McCaghey et al, 2017). Plants were inoculated using the cut petiole inoculation method (Ranjan et al, 2018) and infection progression was monitored in R and S soybean lines over 7 days.…”

“…Our recent breeding efforts led to the identification of several recombinant inbred lines (RILs) highly resistant to S. sclerotiorum (McCaghey et al ., ), using the soybean line W04‐1002 as the main source of resistance (Peltier et al ., ). After multiple generations of greenhouse selection, we have chosen two RILs originating from the same cross: one resistant (91‐145) and one susceptible (91‐44) to SSR to complete this study.…”

“…In soybean, bi-parental linkage mapping led to the discovery of many quantitative trait loci (QTL) for resistance to this pathogen. Remarkably, a total of 103 QTL on 18 of the 20 soybean chromosomes have been recorded in SoyBase (Grant et al, 2009) with minimal overlap between QTL reported by different studies (Arahana et al, 2001;Huynh et al, 2010;Kim and Diers, 2000;McCaghey et al, 2017;Moellers et al, 2017;Wei et al, 2017). Despite these efforts, gene level and mechanistic details of soybean resistance mechanisms against S. sclerotiorum remain unknown.…”

Exploring the genetics of lesion and nodal resistance in pea (Pisum sativum L.) to Sclerotinia sclerotiorum using genome‐wide association studies and RNA‐Seq

“…Fine‐tuned redox homoeostasis from the initial reducing status to the later oxidative status in plant tissues is important for S. sclerotiorum to switch from the initial biotrophic lifestyle to the later necrotrophic lifestyle (Kabbage, Yarden, & Dickman, ). Studies searching for plant resistance to S. sclerotiorum have found quantitative interactions (McCaghey et al., ), and potential resistance genes included those with functions to maintain ROS and redox stresses during S. sclerotiorum infection (Girard et al., ; Ranjan et al., ; Zhou, Sun, & Xing, ).…”