Abstract
Root-knot nematode is a very destructive pathogen, to which most peanut cultivars are highly susceptible. Strong resistance is present in the wild diploid peanut relatives. Previously, QTLs controlling nematode resistance were identified on chromosomes A02, A04 and A09 of Arachis stenosperma. Here, to study the inheritance of these resistance alleles within the genetic background of tetraploid peanut, an F2 population was developed from a cross between peanut and an induced allotetraploid that incorporated A. stenosperma, [Arachis batizocoi x A. stenosperma]4×. This population was genotyped using a SNP array and phenotyped for nematode resistance. QTL analysis allowed us to verify the major-effect QTL on chromosome A02 and a secondary QTL on A09, each contributing to a percentage reduction in nematode multiplication up to 98.2%. These were validated in selected F2:3 lines. The genome location of the large-effect QTL on A02 is rich in genes encoding TIR-NBS-LRR protein domains that are involved in plant defenses. We conclude that the strong resistance to RKN, derived from the diploid A. stenosperma, is transferrable and expressed in tetraploid peanut. Currently it is being used in breeding programs for introgressing a new source of nematode resistance and to widen the genetic basis of agronomically adapted peanut lines.
Highlights
Root-knot nematode is a very destructive pathogen, to which most peanut cultivars are highly susceptible
Resistance to root-knot nematode (RKN) was evaluated over three years by measuring three traits: Eggs per gram of root (EGR)
EGR, RF and galling index (GI) values for the RBS-F2 were significantly different at P < 0.05 for 2014 and 2016 assays, but not for 2015
Summary
Root-knot nematode is a very destructive pathogen, to which most peanut cultivars are highly susceptible. To study the inheritance of these resistance alleles within the genetic background of tetraploid peanut, an F2 population was developed from a cross between peanut and an induced allotetraploid that incorporated A. stenosperma, [Arachis batizocoi x A. stenosperma]4×. This population was genotyped using a SNP array and phenotyped for nematode resistance. It is highly susceptible to several pests and diseases, including root-knot nematode (RKN) Meloidogyne arenaria (Neal) This is in part due to the absence of gene flow with diploid wild relatives with resistant alleles[7]. Several other cultivars have been released in the U.S using the same source of resistance: NemaTAM, Tifguard, Webb, Georgia-14N and TifNV-High O/L20–24
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