Identifying Varieties and Clones by DNA Typing
DNA marker development is complete. Nineteen markers that were developed in this project, along with six developed in Australia, will provide more than enough for variety identification. These markers have now been characterized and the number of forms in which they exist has been determined. The theoretical maximum number of different DNA profiles that can be distinguished with these markers is over 1039, or more than a trillion times a trillion times a trillion. A set of just the six most informative markers can theoretically produce more than 1 trillion different profiles. The cultivar database, essential both to provide references for identification and also to provide the critical statistical foundation on which estimates of the probability of a particular DNA profile are based, was expanded from 47 to 72 cultivars, all of which have been typed with at least 19 markers. Vines from eight different Petite Sirah vineyards were analyzed and found to be a mixture of Durif, Peloursin and several other varieties, confirming that the name Petite Sirah is used for more than one variety in California. Efforts to promote the use of our grape DNA markers in other countries have been very successful. They are now being used in nine other countries and we hope to be able to exchange valuable information with researchers who have access to highly reliable European variety collections. The modified AFLP approach by which we tried to differentiate Chardonnay and Pinot Noir clones revealed some differences but they were neither sufficiently numerous or reproducible to be of use.