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Abstract
The response of fruit size and fruit size distribution was studied in four peach (Prunus persica L. Batsch.) cultivars (May Crest, June Lady, Elegant Lady, O’Henry) ranging in maturity date from late May to early August (75 to 150 days after bloom). Mature, open-vase trees were thinned to fruit levels ranging from 150 to 2200 fruit per tree. The slopes of the linear relationships between fruit weight and fruit number per tree were consistent among cultivars, but their y-intercepts increased proportionate to maturity date. The standard deviation of individual fruit weights tended to decrease with increasing fruit number per tree and increased with later-maturing cultivars. However, the coefficient of variation remained nearly constant among cultivars. Mean fruit weight generally dropped off with successive harvests, especially on trees with heavy fruit loads. Heavy fruit loads also delayed maturity in all four cultivars. This study measured the variation of fruit weight response to thinning, information that is needed for a detailed economic analysis of thinning to different fruit loads.
Early maturing peach trees [Prunus persica (L.) Batsch cv. Regina] growing on a deep sandy loam soil were subjected to three levels of postharvest irrigation over 4 years. The control treatment was irrigated with ≈ 10 to 15 cm of water at 2- to 3-week intervals, the medium treatment received a single irrigation (20 to 30 cm) in early August, and the dry treatment was not irrigated between early to mid-June and mid-October. All received a predormancy irrigation of 10 to 15 cm in mid- to late October. Flower and fruit density were greater in the dry treatment than the control. The occurrence of double fruit was also greatly increased in the dry treatment but not in the medium treatment, when compared with the control. After normal commercial hand thinning, yields and fruit size were no different among the three treatments over all 4 years. Vegetative growth as measured by dormant pruning weights, trunk radial growth, and canopy shaded area was reduced in the dry treatment, but there was no indication of progressively declining vigor. Soil moisture determinations indicate that water use by the control occurred mainly in the upper soil profile. In the dry treatment, as the upper profile dried, water was extracted progressively deeper, down to at least 300 cm. The main disadvantage of severe postharvest water stress was the substantial increase of double fruits.