title: Genetic mapping and legume synteny of aphid resistance in African cowpea (Vigna unguiculataL. Walp.) grown in California.
abstract: The cowpea aphidAphis craccivoraKoch (CPA) is a destructive insect pest of cowpea, a staple legume crop in Sub-Saharan Africa and other semiarid warm tropics and subtropics. In California, CPA causes damage on all local cultivars from early vegetative to pod development growth stages. Sources of CPA resistance are available in African cowpea germplasm. However, their utilization in breeding is limited by the lack of information on inheritance, genomic location and marker linkage associations of the resistance determinants. In the research reported here, a recombinant inbred line (RIL) population derived from a cross between a susceptible California blackeye cultivar (CB27) and a resistant African breeding line (IT97K-556-6) was genotyped with 1,536 SNP markers. The RILs and parents were phenotyped for CPA resistance using field-based screenings during two main crop seasons in a 'hotspot' location for this pest within the primary growing region of the Central Valley of California. One minor and one major quantitative trait locus (QTL) were consistently mapped on linkage groups 1 and 7, respectively, both with favorable alleles contributed from IT97K-556-6. The major QTL appeared dominant based on a validation test in a related F2 population. SNP markers flanking each QTL were positioned in physical contigs carrying genes involved in plant defense based on synteny with related legumes. These markers could be used to introgress resistance alleles from IT97K-556-6 into susceptible local blackeye varieties by backcrossing.
authors.affiliation: Department of Nematology, University of California, Riverside, CA 92521 USA.
authors.forename: Bao-Lam
authors.initials: BL
authors.lastname: Huynh
authors.affiliation: Bill and Melinda Gates Foundation, Seattle, WA 98102 USA.
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Ehlers
authors.affiliation: Department of Nematology, University of California, Riverside, CA 92521 USA.
authors.forename: Arsenio
authors.initials: A
authors.lastname: Ndeve
authors.affiliation: Department of Botany and Plant Sciences, University of California, Riverside, CA 92521 USA.
authors.forename: Steve
authors.initials: S
authors.lastname: Wanamaker
authors.affiliation: Department of Botany and Plant Sciences, University of California, Riverside, CA 92521 USA.
authors.forename: Mitchell R
authors.initials: MR
authors.lastname: Lucas
authors.affiliation: Department of Botany and Plant Sciences, University of California, Riverside, CA 92521 USA.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Close
authors.affiliation: Department of Nematology, University of California, Riverside, CA 92521 USA.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Roberts
keywords: Biotic stress; Cowpea aphid; Legume; Physical mapping; Vigna unguiculata