Cane productivity and fruit quality in highbush blueberry are affected by cane diameter and location within the canopy

摘要

Cane productivity in blueberries can be affected by their diameter, but the effect of cane spatial location (i.e., position within the canopy) on fruit yield and quality is unknown. This study aimed at assessing for two seasons the effect of cane diameter and location on yield and fruit quality of mature highbush blueberries cv. O'Neal and Brigitta (Vaccinium corymbosum L.). In a field in Romeral, Chile (34 degrees 58'00 '' S, 71 degrees 08'00 '' W), cane diameter was measured at 10 cm from the cane base. Canes were then grouped into three diameter classes: 0-0.9, 1-1.9 and 2-2.9 cm. In every bush, the spatial location of each cane was defined as external (located within 25 cm from the canopy periphery), or internal (those canes growing in the canopy center). Fruit with >80% blue color were harvested every five to seven days from each cane; fruit number and weight, yield, as well as fruit soluble solids, firmness and diameter were determined. Availability of radiation (% full sun: % FS) was measured for cane location and every 30 cm from top to the base of the canopy. The extension of the productive zone (cm) was established for each cane according to its location and diameter. Fruit firmness, weight loss, dehydration, soft fruit and decay were determined after 40 d storage (0 degrees C and 90% HR). For both years external canes had on average higher yield (67% for 'Brigitta'; 69% for 'O'Neal') and fruit number (54% for 'Brigitta'; 62% for 'O'Neal') than internal canes. Yield increased with greater cane diameter and this was due mainly to larger fruit number per cane. Fruit number and yield per cane were highly correlated for both varieties and seasons (r(2) >= 0.86). In the first season for cv. O'Neal, fruit weight was higher (34%) in 0-0.9 cm canes than in canes >1 cm diameter. In cv. Brigitta, no differences were found for fruit weight. For cv. O'Neal, soluble solids, firmness and fruit diameter were not affected by cane location or diameter. In cv. Brigitta, external canes had fruit with lower soluble solids (13.1 degrees Brix) than internal ones (14.4 degrees Brix). Fruit diameter in 'Brigitta' was significantly higher in canes with diameters >1 cm. Cane diameter and location did not affect fruit weight loss after 40 d storage in cv. O'Neal. In cv. Brigitta, fruit weight loss was higher in 0-0.9 cm canes than in 1-1.9 cm canes. The productive zone in external canes as compared to internal canes was 32% higher for cv. O'Neal and 38% for cv. Brigitta. The extent of the productive zone was greater (56-72%) in thicker canes. Availability of radiation was higher for external (42% FS) than internal canes (27% FS). Radiation decreased from the top to the base of the plant (from 51% to 18% FS). As in the canopy center the intensity of radiation was lower, this would have reduced the productive area of those canes, which would have induced lower fruit numbers ending up in decreased yield but with little effect on fruit quality. Orchard practices should aim at increasing light availability in the center of canopies to maintain high flower number and high yields.