Originally published as Genetics Published Articles Ahead of Print on January 12, 2009.

Genetics, Vol. 181, 1115-1127, March 2009, Copyright © 2009
doi:10.1534/genetics.108.094268

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

Karolina Pajerowska-Mukhtar^*,1,2, Benjamin Stich^,1,3, Ute Achenbach^*,1,4, Agim Ballvora^*, Jens Lübeck, Josef Strahwald, Eckhard Tacke, Hans-Reinhard Hofferbert^**, Evgeniya Ilarionova^*,5, Diana Bellin^*,6, Birgit Walkemeier^*, Rico Basekow^,7, Birgit Kersten^,7 and Christiane Gebhardt^*,8

^* Max Planck Institute for Plant Breeding Research, Department for Plant Breeding and Genetics, 50829 Cologne, Germany, Institute for Plant Breeding, Seed Science, and Population Genetics, University of Hohenheim, 70593 Stuttgart, Germany, Saka Pflanzenzucht GbR, Zuchtstation Windeby, 24340 Windeby/Eckernförde, Germany, Bioplant GmbH, 29574 Ebstorf, Germany, ^** Böhm-Nordkartoffel Agrarproduktion GbR, 29574 Ebstorf, Germany and Former RZPD German Resource Center for Genome Research GmbH, 14059 Berlin, Germany

⁸ Corresponding author: Max Planck Institute for Plant Breeding Research, Department for Plant Breeding and Genetics, Carl von Linné Weg 10, 50829 Cologne, Germany.
E-mail: gebhardt{at}mpiz-koeln.mpg.de

The oomycete Phytophthora infestans causes late blight, the most relevant disease of potato (Solanum tuberosum) worldwide. Field resistance to late blight is a complex trait. When potatoes are cultivated under long day conditions in temperate climates, this resistance is correlated with late plant maturity, an undesirable characteristic. Identification of natural gene variation underlying late blight resistance not compromised by late maturity will facilitate the selection of resistant cultivars and give new insight in the mechanisms controlling quantitative pathogen resistance. We tested 24 candidate loci for association with field resistance to late blight and plant maturity in a population of 184 tetraploid potato individuals. The individuals were genotyped for 230 single nucleotide polymorphisms (SNPs) and 166 microsatellite alleles. For association analysis we used a mixed model, 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. A major association was found at the StAOS2 locus encoding allene oxide synthase 2, a key enzyme in the biosynthesis of jasmonates, plant hormones that function in defense signaling. This finding supports StAOS2 as being one of the factors controlling natural variation of pathogen resistance.

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