Iso-lines and inbred-lines confirmed loci that underlie resistance from cultivar ‘Hartwig’ to three soybean cyst nematode populations

Abstract

Soybean [Glycine max (L.) Merr.] cultivars varied in their resistance to different populations of the soybean cyst nematode (SCN), Heterodera glycines, called HG Types. The rhg1 locus on linkage group G was necessary for resistance to all HG types. However, the loci for resistance to H. glycines HG Type 1.3- (race 14) and HG Type 1.2.5- (race 2) of the soybean cyst nematode have varied in their reported locations. The aims were to compare the inheritance of resistance to three nematode HG Types in a population segregating for resistance to SCN and to identify the underlying quantitative trait loci (QTL). 'Hartwig', a soybean cultivar resistant to most SCN HG Types, was crossed with the susceptible cultivar 'Flyer'. A total of 92 F5-derived recombinant inbred lines (RILs; or inbred lines) and 144 molecular markers were used for map development. The rhg1 associated QTL found in earlier studies were confirmed and shown to underlie resistance to all three HG Types in RILs (Satt309; HG Type 0, P = 0.0001 R (2) = 22%; Satt275; HG Type 1.3, P = 0.001, R (2) = 14%) and near isogeneic lines (NILs; or iso-lines; Satt309; HG Type 1.2.5-, P = 0.001 R (2) = 24%). A new QTL underlying resistance to HG Type 1.2.5- was detected on LG D2 (Satt574; P = 0.001, R (2) = 11%) among 14 RILs resistant to the other HG types. The locus was confirmed in a small NIL population consisting of 60 plants of ten genotypes (P = 0.04). This QTL (cqSCN-005) is located in an interval previously associated with resistance to both SDS leaf scorch from 'Pyramid' and 'Ripley' (cqSDS-001) and SCN HG Type 1.3- from Hartwig and Pyramid. The QTL detected will allow marker assisted selection for multigenic resistance to complex nematode populations in combination with sudden death syndrome resistance (SDS) and other agronomic traits.

The receptor like kinase at Rhg1-a/Rfs2 caused pleiotropic resistance to sudden death syndrome and soybean cyst nematode as a transgene by altering signaling responses

“…Interestingly most of these PIs were also partially resistant to SDS [14]. One locus, the Rfs2/Rhg1 locus on chromosome 18, was shown to underlie coinheritance of resistance to SDS in the roots and also reduce root infestation by SCN [10,11,14-17]. Fine map development did not resolve Rfs2 from Rhg1 suggesting the underlying gene(s) were either very closely linked or pleiotropic [11,16].…”

“…However, the Rhg1 locus was constant, being required for partial resistance to all Hg Types in most PIs and cultivars. Full resistance to SCN required 1–4 loci in addition to Rhg1 , the number depending on the nature of the cyst population parasitizing the roots [17,21-25]. Genetic diversity was found among SCN isolates, even inbred cyst populations like PA3, Hg type 0 [13,26].…”

“…In crosses based on Forrest and with SCN isolate PA3 the rhg1-a was shown to be codominant with the susceptibility allele of ‘Essex’ ( rhg1 -e) and alone capable of providing partial resistance. Consequently, the Forrest, ‘Hartwig’, Peking and ‘PI 437654’ allele was renamed to Rhg1-a ([17] and hereafter) by the Soybean Genetics Committee.…”

Identification of Loci Underlying Seed Yield in Recombinant Inbred and Near Isogeneic Soybean Lines Derived from Flyer by Hartwig

“…Linkage was reported as significant if the two statistics for a marker were significant. The use of lower LOD values has been justified previously (Hnetkovsky et al, 1996;Prabhu et al, 1999;Kazi et al, 2007Kazi et al, , 2008Kazi et al, , 2010.…”

“…Hartwig was lower yielding but consistently resistant to SDS in most locations (Njiti et al, 1997(Njiti et al, , 2001Mueller et al, 2003) and strongly resistant to most HG Types of SCN (Anand 1992). Flyer was higher yielding but susceptible to most SCN HG Types and to SDS (Yuan et al, 2002;Kazi et al, 2007Kazi et al, , 2008Kazi et al, , 2010.…”