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O-2
Additional homologs of the Ren1 locus exist in Middle Eastern Vitis vinifera
S. Riaz*, A. Tenscher, M.A. Walker
Department of Viticulture & Enology, University of California, Davis, California, USA
*Corresponding author: snriaz@ucdavis.edu
The discovery of the powdery mildew resistance locus, Ren1, in two Central Asian Vitis vinifera
cultivars, ‘Kishmish vatkana’ and ‘Dzhandzhal’, was an important contribution to powdery
mildew resistance breeding. Allelic information on the SSR markers flanking this locus enabled
the screening of additional germplasm in search of other homologs carrying powdery mildew
resistant genes. This study screened 368 accessions of table and wine grape varieties that
originated from the Middle East, Afghanistan, Turkmenistan, Pakistan and Central Asia, as well
as Chinese Vitis species and hybrid direct producers of Native American Vitis species origin. In
the first round of tests, six international standard SSR markers were used on the complete set of
accessions to identify synonyms and homonyms. In the second round, ten additional markers
sourced primarily from chromosome 12, 13 and 18 were utilized on a set of 263 unique
accessions. The allelic diversity of marker VMCNg4e10.1 and UDV124 that flank the Ren1
locus was investigated. Thirty-one accessions were identified that had the 216 bp allele for
marker UDV124 and 30 accessions had the 260 bp allele of marker VMCNg4e10.1, both of
which have been associated with Ren1. The six accessions with resistant alleles for both markers
included two cultivars with known resistance to powdery mildew, ‘Kishmish vatkana’ and
‘Karadzhandal’ (a synonym for ‘Dzhandzhal’), and four other cultivars ‘Husseine’, ‘Late
Vavilov’, ‘Sochal’, and ‘Black Kishmish’. All of the accessions with one or both alleles linked to
resistance were screened under field conditions conducive to powdery mildew infection.
Preliminary results indicate that the four additional homologs of Ren1 have significant resistance
to powdery mildew.
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