Association mapping for kernel phytosterol content in almond.

Carolina Font I Forcada,Ángel Fernández I Martí,Leonardo Velasco,Rafel Socias I Company

doi:10.3389/fpls.2015.00530

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 r2-value for all intra-chromosomal loci pairs was 0.040, whereas, the r2 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.

Highlights

Almond is the most important source of nut tree oils worldwide and is well ranked among the oil crops
Phenotypic Variation in the Almond Germplasm The phenotypic variability of the phytosterol content and profile was large, reflecting the wide coverage of the almond gene pool reached by the 71 cultivars studied
We identified seven markers associated with phytosterol content in almond

Summary

Introduction

Almond is the most important source of nut tree oils worldwide and is well ranked among the oil crops (http://faostat.fao.org). Almond breeding has been until recently focused on selecting self-compatible and late-blooming cultivars with fruits of a high physical quality (Socias i Company et al, 2012). Very little information on the chemical evaluation of the almond kernel has been reported and the studies on the chemical components of the almond kernel and their variability are scarce (Socias i Company et al, 2008). Incorporation of such parameters in the evaluation of new crosses would be of special relevance in determining the possible commercial and industrial uses of the kernels, since their specific use depends primarily on its chemical composition (Socias i Company et al, 2008). Among the chemical parameters evaluated in recent years, the most important have been fatty acid

Methods

Results

Discussion

Conclusion