Issue link: http://read.dmtmag.com/i/108963
T o obtain a poster developed to help growers identify different berry shrivels, contact Bondada at bbondada@tricity.wsu.edu. For more information about grape shrivels, visit his Web site at: http://wine.wsu.edu/ faculty/bhaskar-bondada/. IDENTIFYING grape shrivels I Photo courtesy of Wsu n the past, grape growers have mistaken any shrivel in their fruit for grape berry shrivel, also known as sour shrivel, says Washington State University���s Dr. Bhaskar Bondada. In a panic, some were needlessly thinning clusters to remove what they thought were berries afflicted with sour shrivel. It���s important to know the difference between shrivels because fruit from some types can still be made into wine, but grapes with sour shrivel can���t. To help growers identify grape shrivels, Bondada and his colleagues have developed diagnostic keys for various ripening disorders in the form of a poster with photos to provide characteristics and distinguishable features of the different shrivels. Several theories about the cause of sour shrivel have been disproven in past WSU research. Bondada���s current focus is on the mechanics of sour shrivel, comparing the structure and functionality of vascular pathways (the xylem and phloem) of the whole bunch stem of healthy and sour shrivel afflicted vines. The research involves simulating sour shrivel symptoms under greenhouse conditions and examining vascular pathways, especially phloem that translocates sugar, in different organs for some kind of occlusion that may be impeding sugar flow into the berries. ���M. Hansen Berry or sour shrivel grapes look like a deflated soccer ball, with the flesh collapsed. ���The clusters are not suitable for making wine,��� he said. Fruit from the other disorders (sunburn, dehydration, or bunch stem necrosis) still have some desirable fruit characteristics and can be used to make some types of wine. ���But not sour shrivel. It���s one that you don���t want in your vineyard.��� Berries exhibiting dehydration take on a dimpled, golf ball look. GrAPe Photos courtesy of BhAskAr BondAdA Good, bad, and ugly Not all the fruit on afflicted clusters show the symptoms of sour shrivel. Rarely is the whole cluster affected, he said, adding that symptoms are typically found at the bottom of the cluster. ���If the whole cluster is affected, then it means you���re losing a lot of crop.��� Bondada found three types of berries in cluster showing sour shrivel���relatively healthy berries (the good) that were only two or three degrees lower in Brix than normal berries from a healthy cluster. No significant differences were observed between healthy and healthy shrivel berries in tartaric acid or pH levels. ���But then you have the bad, which are berries lighter in color. And then there���s the ugly���flaccid, sour-tasting berries,��� he said. Red and white varieties are both affected by the disorder. Bondada has seen sour shrivel in the white varieties of Sauvignon Blanc, Chardonnay, Semillon, and Riesling. In reds, it���s been found in Washington in Cabernet Sauvignon, Merlot, and Petite Syrah. ���Among the red varieties, Cabernet is the poster child,��� he said. ���Every year, we see it in Cabernet blocks somewhere in the state.��� Bondada said that the latest victim is Grenache, adding that he���d never seen sour shrivel in Grenache until this past year. Scientists believe that because the sour shrivel fruit are not getting water and sugar���but the seeds are normal���that the disorder is initiated after veraison. Bondada adds that by using fluorescent dyes and high-powered microscopes, scientists can examine cell structures within the flesh and other vegetative and reproductive parts of the grapevine. The fluorescent dyes have shown that sour shrivel berries lose membrane integrity of their juice cells, the tiny bags that accumulate sugars and acids. Bondada shared his findings during the annual meeting of the Washington State Grape Society. ��� A normal, healthy grape berry. GOOD FRUIT GROWER FEBRUARY 15, 2013 25