Jean Dodson Peterson
The majority of winegrape cultivars (Vitis vinifera L.) are susceptible to damage and eventual decline by the root aphid, phylloxera, as well as various species of nematodes. Therefore, commercial winegrapes are typically grafted to hybrid crosses of North American Vitis species, which have evolved tolerance to these pest pressures. Rootstock parentage is carefully considered when making a commercial rootstock selection, as well as, the specific type of grafted plant purchased for use in vineyard establishment (green-growing, dormant). Dormant bare-rooted benchgrafts are grafted, callused, and then field grown in a nursery block row for one season before being dug up in the late fall or winter to be sold and planted. Green-growing benchgrafts are first grafted when dormant, callused, potted or put into sleeves, transferred to the greenhouse and eventually moved to a shade house where they acclimate to outdoor conditions for planting in the same year in which they were grafted. Traditionally, dormant bare-rooted bench grafts are considered superior to green-growing benchgrafts based on the assumption that they have higher capacity and potential vigor. Vine vigor is a measure of growth over time while vine capacity is a measure of total yearly biomass (vegetation and fruit) produced. Prior studies have shown a relationship between vine vigor and capacity indices as a function of root and trunk non-structural total carbohydrate reserves. The purpose of this study was to evaluate first-year growth of grapevines and determine the influence of rootstock selection on vineyard establishment and performance of green-growing benchgrafts. This study used five commercially available rootstock selections, of various parentage, grafted onto Vitis vinifera L. cv. Sauvignon blanc. The research vineyard was designed as a randomized block design with North- South rows on 1.8 x 2.5 meter (vine x row) spacing. Vine development was tracked on a weekly basis beginning at budbreak and was followed until vines reached full dormancy. Total shoot length, cane internode length and cane diameter were measured on a weekly basis during the growing season. Stomatal conductance, density and size are currently in the process of being analyzed. In addition, photosynthetic activity were determined using the LI-6400XT (LICOR Biosynthesis, Lincoln NE). Once vines reached dormancy non-structural carbohydrates were determined by collecting root and trunk wood samples. Pruning weights and trunk diameter were also determined at the time of dormant wood collection.
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