ViLHair – genetic determinants of wild Vitis accessions for trichome density as physical barrier against Plasmopara viticola

Abstract

Grapevine downy mildew caused by Plasmopara viticola is a highly adapted, obligate biotrophic pathogen. It is able to infect all green tissues of a grapevine under suitable conditions, including flowers and unripe grape clusters. Next to elaborate plant protection regimes, natural genetic resistances are employed to cope with this highly infectious and devastating pathogen. However, resistances used in breeding programs so far are most likely based on dominant resistance-genes (R-genes) such as nucleotide-binding leucine-rich-repeat (NLRs) genes. Mutations in and sexual recombination of the pathogens’ genetic material can lead to resistance-breaking isolates, which are able to overcome these natural genetic resistances and thereby counteract decades of laborious breeding efforts to develop disease-resistant varieties.

Trichome density on the abaxial side of grapevine leaves has long been recognized as a first physical barrier that might help to prevent P.viticola zoospores to find their way to stomata. Studies on the genetics of leaf trichomes have so far identified two major QTLs correlating with absence (Leaf Hair 1, LH1, chr. 5, inherited from V. vinifera) and increased trichome density (Leaf Hair 2, LH2, chr. 17, inherited from V. pseudoreticulata). ViLHair focuses on understanding the genetics of trichome formation / density of wild Vitis accessions with diverse backgrounds. Mapping progenies of individuals with naturally very dense trichomes on the abaxial side of the leaf crossed with glabrous leaf V. vinifera accessions are being investigated. Dense genetic maps based on the established high-throughput rhAmpSeqmarker technology are generated and used to map recorded segregating traits.