Linking Candidate Genes to Biochemical Phenotypes in Avocado

This 3-year project, funded jointly by the UC Discovery Program and the CAC, is approaching the end of its final year. It was designed to identify genetic markers that track the nutritional composition of avocado fruit (“nutritional phenotypes”) for implementation via marker-assisted selection. The discovery of candidate genes and development of SNP (Single Nucleotide Polymorphism) markers is complete, though additional markers are expected from
transcription factors involved in the regulation of gene expression. Determination of nutritional composition, phenotypic heritability, and associations between nutritional phenotypes and SNP markers has progressed well. Heritability analyses suggest that proanthocyanidin (the precursor compound of anthocyanins), carotenoid and especially sitosterol contents have a genetic component, and selection for genes from their biosynthetic pathways is expected to produce rapid breeding advance. SNPs of genes from the anthocyanin, carotenoid and sitosterol pathways were found to be associated with elevated nutritional contents of the fruit; the association was very highly significant for a gene from the sitosterol pathway.