title: Association mapping for kernel phytosterol content in almond.
abstract: Almond kernels are a rich source of phytosterols, which are important compounds for human nutrition. The genetic control of phytosterol content has not yet been documented in almond. Association mapping (AM), also known as linkage disequilibrium (LD), was applied to an almond germplasm collection in order to provide new insight into the genetic control of total and individual sterol contents in kernels. Population structure analysis grouped the accessions into two principal groups, the Mediterranean and the non-Mediterranean. There was a strong subpopulation structure with LD decaying with increasing genetic distance, resulting in lower levels of LD between more distant markers. A significant impact of population structure on LD in the almond cultivar groups was observed. The mean r(2) -value for all intra-chromosomal loci pairs was 0.040, whereas, the r(2) for the inter-chromosomal loci pairs was 0.036. For analysis of association between the markers and phenotypic traits five models were tested. The mixed linear model (MLM) approach using co-ancestry values from population structure and kinship estimates (K model) as covariates identified a maximum of 13 significant associations. Most of the associations found appeared to map within the interval where many candidate genes involved in the sterol biosynthesis pathway are predicted in the peach genome. These findings provide a valuable foundation for quality gene identification and molecular marker assisted breeding in almond.
authors.affiliation: Genome Center, University of California, Davis Davis, CA, USA.
authors.forename: Carolina
authors.initials: C
authors.lastname: Font I Forcada
authors.affiliation: Instituto de Agricultura Sostenible, Consejo Superior Investigaciones Científicas Córdoba, Spain.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Velasco
authors.affiliation: Unidad de Hortofruticultura, Centro de Investigación y Tecnología Agroalimentaria de Aragón Zaragoza, Spain.
authors.forename: Rafel
authors.initials: R
authors.lastname: Socias I Company
authors.affiliation: Genome Center, University of California, Davis Davis, CA, USA ; Unidad de Hortofruticultura, Centro de Investigación y Tecnología Agroalimentaria de Aragón Zaragoza, Spain.
authors.forename: Ángel
authors.initials: Á
authors.lastname: Fernández I Martí
keywords: Prunus amygdalus; SSR markers; candidate genes; genetic variability; linkage disequilibrium; population structure; sterol content