Location: Southern Horticultural ResearchTitle: Water Uptake Threshold of Rabbiteye (Vaccunium ashei) Blueberries and its Influence on Fruit Splitting Author
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/2009
Publication Date: 12/1/2009
Citation: Marshall, D.A., Spiers, J.M., Curry, K.J. 2009. Water Uptake Threshold of Rabbiteye (Vaccunium ashei) Blueberries and its Influence on Fruit Splitting. HortScience. 44(7):1-3 pgs 2035-2037. Interpretive Summary: Water uptake thresholds are cultivar-dependent, and the difference exists from early fruit development. The splitting susceptible ‘Tifblue’ had a smaller increase in weight from water absorption as it matured than did ‘Premier’ the splitting resistant rabbiteye counterpart. ‘Premier’ consistently increased in weight by approximately 4% of the fruit original weight. ‘Premier’ exhibited minimal splitting, even in early development. This split fruit should drop off and pose little problems to yields at the grading line. In contrast, ‘Tifblue’ exhibited no splitting during early development, yet when the fruit became commercially ripe the percentage of splitting dramatically increased. The commercially ripe stage is the time that the fruit yields are significantly affected by the splitting. Ripe, split fruit that are machine or hand harvested are rejected at the grading line, sometimes causing the entire batch to be rejected if the number of splits found is high enough. This would greatly reduce a growers profit and income. It is clear from this study and previous studies (Marshall, 2001; Marshall et al., 2006,2007) that rain induced splitting is a problem that especially effects growers and producers. It is also clear that the splitting phenomenon is a cultivar specific problem. This study further shows that both cultivars tested absorb water into the fruit at a linear rate. The difference occurs in how the fruit handles the water that is absorbed. Are the cells filling and expanded past controllable capacity, or are the cells remaining intact and the cell-to-cell adhesions giving way. This study provides a starting point for further studies already in progress looking at cell-to-cell adhesion and possible air space within the pulp of the fruit. These adhesion points and air spaces will be quantified and evaluated for possible causes of rain-related splitting in cultivated blueberries.
Technical Abstract: Splitting resistant and splitting susceptible Rabbiteye blueberry fruit were evaluated at all stages of development to determine water uptake thresholds by soaking in distilled water. Weight increase after soaking was measured, and percent weight gain was calculated to take into consideration the weight increase of the fruit from development. The ratio of percent increase in volume to weight increase due to water uptake was calculated. Ratios of percent water uptake to weight increase between splitting susceptible ‘Tifblue’ and splitting resistant ‘Premier’ blueberries were found to be similar. The splitting susceptible ‘Tifblue’ had a 1.6 g/50 fruit increase with a 1.7% water uptake. This would provide a ratio of 1.08 for ‘Tifblue.’ The splitting resistant ‘Premier’ had a higher weight increase with 3.3 g/50 fruit, but also a higher percentage of water uptake at 3.6% providing a ratio of 1.09. Even though both absorbed water at a constant rate shown by a linear increase of weight increase over time, ‘Premier’ absorbed a significantly greater amount of water than did ‘Tifblue’. This study provides a starting point for further studies that are in progress.