Meeting discusses winegrape rootstock, winery sanitation
and photosynthesis during drought. Maintaining a greater root volume in- creased water uptake fromdry soil. But in vineyard conditions, rootstocks develop deep, variable rooting environ- ments, she said. Viticultural drought tol- erance reflects better connectivity with wet soil, and drought-tolerant rootstocks lose more turgor in dry roots. Anita Oberholster, UC Cooperative extension specialist in enology at UC Davis, looked at cleaning and sanitation inwineries. She descibed it as “a preven- tive process, not a corrective one.” Oberholster said it is important tohave written protocols to “ensure product quality and worker safety.” Benefits include improved product quality, reduced operating costs, lon- ger equipment life and a safe working environment. Costs and consequences of poor cleaning and sanitation include spoiled or unsaleable product, a dam- aged reputation, damaged equipment and hazardous conditions. Oberholster said cleaning involves removal of organic and inorganic soils. Sanitizing involves disinfection, sanita- tion and sterilization: Disinfection re- sults in 99.9% reduction in harmful or pathogenic cells; sanitation is effective elimination of potential spoilage mi- crobes; sterilization is elimination of all viable cells. Common cleaning chemistries in- clude caustic and non-caustic prod-
ucts as well as acid cleaners, she said. Sanitizing chemistries include peracetic acid, use of ozone, heat and steam, and othermeans such as ultraviolet light and ultrasonic applications. Oberholster said there should be writ- ten protocols and employee checklists, along with a monitoring strategy to val- idate protocol. She saidwinery tank surfaces and bot- tling lines are often the areasmost free of microbial contamination, whereas drains and the areas around the bung of barrels may have high levels. Pumps, hoses and winery process water often can cause re- contamination. “It’s important to pay attention to crit- ical areas such as valves, gaskets and ports, and to take care in cleaning floors, especially with hose water,” Oberholster said. “Develop a strategy for monitoring the success of a protocol. Visual clean is not good enough.” She said there is “no right or wrong choice for cleaning and sanitizing chemi- cals. Choices should depend on the bud- get, the application surface, regulations or personal preference, but should be validated by a monitoring program.” “Even when visually clean, a clean- ing step cannot be omitted or the risk of contamination frombiofilms will occur,” Oberholster said. (Denni s Pol lock i s a repor t er in F r e s no . He ma y b e c on t a c t e d a t agcompollock@yahoo.com.)
ByDennis Pollock Girding grape rootstock with drought tolerance and cleaning and sanitation in winerieswere among topics taking center stage at a virtual meeting conducted by University of California researchers. Megan Bartlett, assistant professor with the Department of Viticulture and Enology atUCDavis, opened theVirtually on the Road in Stanislaus County meet- ing by talking of evaluating traits to im- prove drought tolerance in rootstocks. She said her research aims to evaluate candidate rootstock traits for ability to maintainphotosynthesis and growthun- der water-stressed conditions. Bartlett said the lack of geneticmarkers forwater-related traits has impededprog- ress in breeding efforts. She said many traits have been linked with drought tol- erance in crop and wild plant species, though it remains difficult to identify a set of genes to target in breeding efforts. It has been learned that root cellular traits impact root sensitivity to drought. Roots are a major bottleneck for plant water transport, especially under water stress, she said, because most resistance to water movement comes from living cells in the roots. Cell collapse in grapevine roots lim-
its water uptake during drought, Bartlett said. X-ray imaging of drought-starved roots showedcell collapse anddeath start early inwater stress, which reduceswater uptake from the soil. Root cells shrink as they lose water and turgor declines, meaning they lose the water pressure that holds up the cell walls as they lose water. The shrinking of root cells results in loss of pathways for water movement. Bartlett’s research looked at the de- gree to which rootstocks vary in the sensitivity to water stress and whether those traits can be changed to improve drought tolerance. Researchers looked at eight grafted rootstocks that vary indrought tolerance. They grew potted vines in a greenhouse that standardized drought treatment by eliminating the effect of differences in rooting depth. Pots were watered and weighed three times per week to main- tain soil content at 100% (well-watered) and 40% (drought). Plant measurements included stomatal conductance, photo- synthesis, midday leaf water potential and evapotranspiration. Bartlett said the study found that root- stocks with less root shrinkage main- tained greater stomatal conductance
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September 9, 2020 Ag Alert 11
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