Microsatellite markers associated with a secondary stem solidness locus in wheat

Wheat, Triticum aestivum L., genotypes with pith-filled, or solid, stems impede the development of the wheat stem sawfly (WSS), Cephus cinctus N., and thus provide a measure of control. A high degree of solidness confers the greatest level of resistance to the sawfly. A previous study allowed identification of a major gene on chromosome 3B of wheat that controlled 75% of the variation for solidness in a hollow-stemmed by solid-stemmed cross. Stems of lines containing the allele for solidness often were of an intermediate solidness that would not confer sufficient resistance to the sawfly. To identify secondary genes, we conducted a cross between a solid-stemmed line and a tine with intermediate solidness. A set of 94 recombinant inbred lines were analyzed for stem solidness and agronomic traits in four environments. Bulk segregant analysis was used to screen 149 polymorphic microsatellite markers. A locus on chromosome 3D, designated Qss.msub-3DL, was identified that controlled 31% of the variation for solidness in this cross. No negative correlation was observed with yield in any environment. Selection for the solid stem alleles on chromosomes 3B and 3D using marker-assisted selection will be useful for rapid development of new solid-stemmed genotypes.