Genotyping of the Valencia Peanut Core Collection with a Molecular Marker Associated with Sclerotinia blight Resistance

Abstract

Cultivated peanut, the second most economically important legume crop throughout the United States and the third most important oilseed in the world, is consistently threatened by various diseases and pests. Sclerotinia blight, (causal agents Sclerotinia sclerotiorum (S. sclerotiorum) and Sclerotinia minor Jagger (S. minor))is a major threat to peanut production in the Southwestern U.S., Virginia, and North Carolina and can reduce yield by up to 50% in severely infested fields. S. sclerotiorum has now been reported in areas of eastern New Mexico and west Texas where all U.S. grown Valencia peanuts are produced, commonly in organic cropping environments. Host plant resistance provides the most effective solution to managing Sclerotinia blight, especially in organic systems where pesticide use is not an option for disease control. To date, no Valencia cultivars with Sclerotinia blight resistance have been released. In this study, the Valencia peanut core germplasm collection was genotyped with a Simple Sequence Repeat (SSR) marker associated with Sclerotinia blight resistance in order to identify potential germplasm for use in breeding to develop Valencia peanut cultivars resistant to the disease. Thirty accessions from the Valencia peanut core collection have profiles consistent with other genotypes that exhibit less that 5% incidence of Sclerotinia blight under heavy disease pressure. The identified accessions, after field evaluation, may serve as potential sources of Sclerotinia blight resistance in Valencia peanut breeding programs.

Screening of the Argentinean INTA peanut core collection with a molecular marker associated with resistance to Sclerotinia minor Jaggar

“…Stronger correlations exist for the extremes of susceptibility or resistance (Figure 2A and 2B), whereas the marker is less likely to accurately predict phenotypic reactions in the moderate range (denoted by red ovals, Figure 2). These results are similar to those reported previously by others using this marker to screen other germplasm collections Chamberlin, 2014;Bennett et al, 2018;Chamberlin and Puppala, 2018).…”

“…The interaction between growth habit and Sclerotinia blight resistance on disease incidence may account for the exceptions in the marker analysis. Given that the template DNA has been quantified and normalized across all reactions, band intensity or peak height of the identified resistance and susceptible bands has previously been correlated with level of resistance seen among genotypes tested with this marker system (Chamberlin, 2014;Chamberlin and Puppala, 2018), allowing the prediction of field reaction to S. minor infection for genotypes not yet tested in phenotyping trials. Table 2 lists the botanical variety and genotypic profiles (peak heights) for each entry along with the respective predicted field reaction to S. minor.…”

“…Previously, the marker used in this study was shown to be significantly associated with resistance to Sclerotinia blight in peanut cultivars and PIs that had been thoroughly evaluated in field trials (Chenault et al, 2009). The marker has been used previously to screen numerous germplasm collections Chamberlin, 2014;Chamberlin and Puppala, 2018) and the results obtained have been shown to closely agree with phenotypic reaction to S. minor in field trials (Chenault et al, 2009;Chamberlin et al, 2010;Damicone et al, 2010;Bennett et al, 2018). The results of the current study are similar to those reported when the marker was used to screen other collections, with the marker for resistance being prominent in the fastigiata, vulgaris, and hirsuta botanical types.…”

“…These core collections, along with the development and use of molecular markers associated with key traits, greatly increase the efficiency of mining these vast collections for sources of breeding material to enhance cultivated peanut. A molecular marker associated with Sclerotinia blight resistance in peanut has been identified (Chenault et al, 2009), and has been used to screen multiple core collections Chamberlin, 2014;Chamberlin and Puppala, 2018).…”

Use of wild and exotic germplasm for resistance in peanut

“…In addition, Clevenger, Chu, et al (2018) used QTLseq to identify multiple QTLs for LLS resistance in peanuts; they applied QTL mapping, backward selection, blind selection, and 4 yr of field data to validate the significant QTLs. Simple sequence repeat markers ampli-fying 115-bp bands screened for sclerotinia blight resistance in the valencia peanut core collection, and 30 accessions were reported to be highly resistant to sclerotinia blight in the valencia market type (Chamberlin & Puppala, 2018). In association mapping studies to detect QTL controlling TSWV resistance in cultivated peanuts, five markers (pPGPseq5D5, GM1135, GM1991, TC23C08, and TC24C06) have been reported to be significantly associated with TSWV resistance.…”