Phenotypic and Haplotype Diversity among Tetraploid and Hexaploid Wheat Accessions with Potentially Novel Insect Resistance Genes for Wheat Stem Sawfly

Abstract

Genetic diversity in breeding programs can be impaired by fixation of alleles derived from a limited number of founder lines. This is demonstrated with the use of a solid-stem trait derived from the Portuguese landrace 'S-615' over 70 yrs ago that is widely used to resist the wheat stem sawfly (Cephus cinctus Norton, WSS) in North America. The objective of this study was to evaluate haplotype diversity underlying the Qss.msub.3BL quantitative trait locus (QTL) that controls the majority of the S-615 derived solid-stem genetic variation using single-nucleotide polymorphism (SNP) assays in a diverse set of 228 solid-stem tetraploid and hexaploid wheat accessions originating from areas of the world infested with various species of WSS. Haplotype analysis showed all WSS-resistant hexaploid wheat varieties in North America, except 'Conan', evaluated in this study contain a haplotype associated with the S-615 solid-stem allele. In total, 26 haplotypes were identified among the hexaploid and tetraploid accessions at Qss.msub-3BL. Prevalence of most haplotypes were skewed toward either the hexaploid or tetraploid wheat accessions. The haplotype found in the S-615-hexaploid wheat landrace was not found in the solid-stem tetraploid landrace accessions evaluated in this study. Haplotype analysis revealed several new haplotypes that have potential to contain novel alleles for solid-stems at Qss.msub.3BL, which may form the basis for introducing genetic diversity into breeding programs aimed at WSS resistance.

Characterization of resistance to the wheat stem sawfly in spring wheat landrace accessions from targeted geographic regions of the world

“…Genomic DNA was isolated from young leaf tissue using a 96-well plate protocol (Chao and Somers, http://maswheat.ucdavis.edu/PDF/DNA0003.pdf, accessed February 2017) modified from Pallotta et al (2003). Five KASP markers, BS00022441, BS00079029, IWB72657, BS00073411, and BS00074345 were used to characterize the haplotype diversity for the solid stem QTL, Qss.msub.3BL, as identified by Cook et al (2017). KASP assays were performed following the protocol and conditions given in the KASP manual (http://www.lgcgroup.com/) as described by Cook et al (2017).…”

“…Five KASP markers, BS00022441, BS00079029, IWB72657, BS00073411, and BS00074345 were used to characterize the haplotype diversity for the solid stem QTL, Qss.msub.3BL, as identified by Cook et al (2017). KASP assays were performed following the protocol and conditions given in the KASP manual (http://www.lgcgroup.com/) as described by Cook et al (2017). Check entries included the hollow-stemmed variety, McNeal, semi-solid stemmed variety, Conan, and solid-stemmed variety, Choteau.…”

“…The resistance allele was also mapped to Qss.msub-3BL, and conferred high stem solidness early in plant development when WSS females are ovipositing and a low level of stem solidness at maturity. Cook et al (2017) showed that the allele for early stem solidness had a different haplotype based on SNP markers than either the S-615-derived solid stem allele or the common alleles for hollow stems.…”

Farming system and wheat cultivar affect infestation of, and parasitism on, Cephus cinctus in the Northern Great Plains

“…Because penetration of the stem and host location are more difficult for parasitoids; the efficacy of hollow‐stemmed wheat is also dependent on the availability of preferred alternative hosts . Further incorporation of genetic diversity of Triticeae is necessary to increase resistance to climate change, disease, and pests like C. cinctus while maintaining yields …”

“…38 Further incorporation of genetic diversity of Triticeae is necessary to increase resistance to climate change, disease, and pests like C. cinctus while maintaining yields. [39][40][41] Kamut wheat (Triticum turgidum ssp. turanicum McKey), commonly known as Khorasan wheat (hereafter 'Kamut'), is a tetraploid cultivar closely related to durum wheat (Triticum turgidum ssp.…”