Influence of Winter and Summer Pruning on Bush Growth, Yield and Fruit Qualities in the Southern Highbush Blueberry 'Misty'

This study was conducted to determine the effects of winter and summer pruning on bush growth, yield, and fruit quality in the six-year-old southern highbush blueberry (Vaccinium corymbosum L. hybrid) 'Misty'. We compared the effects of winter pruning alone and winter + summer pruning after harvest treatments to unpruned plant controls. The fruits were harvested at eight times during the experiment and the fruit yield, unmarketable fruit yield [decayed berries and small size fruit (width less than 10 mm)], and berry weight were recorded at each harvest. Further, fruit quality parameters for harvested fruits such as soluble solids content (SSC), titratable acidity (TA), firmness, total sugar, total phenolic content, and total anthocyanin content were measured four times after harvest. Moreover, the SPAD value was measured along the plant height; the fresh weight and the ratio of shoot to root volume (T/R) were measured to verify the effects of pruning on vegetative growth. The SPAD values of the lower bush leaves on unpruned blueberry bushes were significantly lower than those recorded from pruned blushes. The highest T/R ratio was observed in the bushes subjected to winter + summer pruning compared to the unpruned bushes. The fruit weight from six-year-old southern highbush blueberry 'Misty' bushes decreased throughout the harvest period in both pruned and unpruned plants. The fruit yield of unpruned blueberry bushes rapidly increased after the 5th harvest; however, the average fruit weight of unpruned blueberry bushes was significantly lower compared to that of pruned blueberry bushes. The considerably higher amount of unmarketable fruit yields was recorded from unpruned blueberry bushes compared to the pruned bushes. The significant differences in measured fruit quality parameters were not observed in harvested fruits from blueberry bushes subjected to winter pruning or winter + summer pruning. The total sugar, phenolic, and anthocyanin content substantially decreased throughout the harvest period in both pruned and unpruned plants.