Single Nucleotide Polymorphisms in the Allene Oxide Synthase 2 Gene are Associated with Field Resistance to Late Blight in Populations of Tetraploid Potato Cultivars

The oomycete Phytophthora infestans causes late blight disease on potato (Solanum tuberosum). Field resistance to late blight is a complex trait controlled by genetic and environmental factors. When cultivated under long day conditions in temperate climates, potato field resistance to late blight is correlated with late plant maturity, an undesirable characteristic. We aim at the identification of genes and their natural variants, which control field resistance to late blight not compromised by late maturity. An association study was conducted in a population of tetraploid potato individuals that were phenotyped in replicated field trials for resistance to late blight and plant maturity. The individuals were genotyped for single nucleotide polymorphisms (SNPs) at candidate loci and for microsatellites to analyze population structure. For association analysis a mixed model was used, taking into account population structure, kinship, allele substitution and interaction effects of the marker alleles at a locus with four allele doses. Nine SNPs were associated with maturity corrected resistance (P < 0.001), which collectively explained 50% of the genetic variance of this trait. The major association with resistance to late blight was found at the StAOS2 locus encoding allene oxide synthase 2. StAOS2 is a key enzyme in the biosynthesis of jasmonates, plant hormones that function in defense signaling.

Key Words: Population genetics, allene oxide synthase 2 (StAOS2), complex traits, late blight, potato (Solanum tuberosum)

Online ISSN: 1943-2361  Print ISSN: 0016-6731
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