ADDITIONAL SOURCES OF REN1-LIKE POWDERY MILDEW RESISTANCE

Abstract

The discovery of the powdery mildew resistance locus, Ren1, in two Central Asian Vitis vinifera cultivars, ?Kishmish vatkana? and ?Dzhandzhal kara?, 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 resistance genes. This study screened 392 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 266 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 6 accessions with resistant alleles for both markers included ?Kishmish vatkana?, ?Karadzhandal? (DVIT2323), a synonym for ?Dzhandzhal kara?, ?Husseine? (DVIT0576), ?Late Vavilov? (UCD Viticulture and Enology), ?Sochal? (DVIT1126), and ?Baidh-ul-Haman? (DVIT0358). 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 four additional homologs of Ren1 have significant resistance to powdery mildew.