Genetic mapping and QTL analysis for peanut smut resistance

AbstractBackgroundPeanut smut is a disease caused by the fungusThecaphora freziiCarranza & Lindquist to which most commercial cultivars in South America are highly susceptible. It is responsible for severely decreased yield and no effective chemical treatment is available to date. However, smut resistance has been identified in wildArachisspecies and further transferred to peanut elite cultivars. To identify the genome regions conferring smut resistance within a tetraploid genetic background, this study evaluated a RIL population {susceptibleArachis hypogaea subsp. hypogaea(JS17304-7-B) × resistant synthetic amphidiploid (JS1806) [A. correntina(K 11905) × A. cardenasii(KSSc 36015)] × A. batizocoi(K 9484)4×} segregating for the trait.ResultsA SNP based genetic map arranged into 21 linkage groups belonging to the 20 peanut chromosomes was constructed with 1819 markers, spanning a genetic distance of 2531.81 cM. Two consistent quantitative trait loci (QTLs) were identifiedqSmIA08andqSmIA02/B02, located on chromosome A08 and A02/B02, respectively. The QTLqSmIA08at 15.20 cM/5.03 Mbp explained 17.53% of the phenotypic variance, whileqSmIA02/B02at 4.0 cM/3.56 Mbp explained 9.06% of the phenotypic variance. The combined genotypic effects of both QTLs reduced smut incidence by 57% and were stable over the 3 years of evaluation. The genome regions containing the QTLs are rich in genes encoding proteins involved in plant defense, providing new insights into the genetic architecture of peanut smut resistance.ConclusionsA major QTL and a minor QTL identified in this study provide new insights into the genetic architecture of peanut smut resistance that may aid in breeding new varieties resistant to peanut smut.