EFFECT OF DEFOLIATION ON THE YIELD AND QUALITY OF ‘PRATA COMUM’ BANANA FRUITS

ABSTRACT With the advent of black sigatoka in commercial banana crops in the “Vale do Ribeira” region, state of São Paulo, the monitoring the severity and chemical control of the disease in susceptible varieties have become more frequent in order to avoid leaf loss. This study simulated the effect of defoliation caused by the disease on the yield and quality of ‘Prata Comum’ banana fruits, depending on the formation period and fruit position in the bunch. The experimental design was completely randomized in a 2 x11 factorial scheme (period of bunch formation x number of leaves at flowering), 6-16 leaves at flowering in two periods of bunch formation with six replicates. In Period 1, flowering occurred at 04/15/13 and in Period 2 at 01/07/14, although in Period 1, bunch mass was higher and in Period 2, higher average maximum and minimum daily temperatures, precipitation and radiation were observed. Regardless of formation period, the number of leaves at flowering affected bunch mass, which ranged from 18 to 23 kg plant-1. Defoliation affected the size of fruits of hand 1 and last hand of the bunch, but not the variability in fruit size due to the position the fruit occupies in the bunch and physicochemical characteristics.摘要 随着黑条叶斑病（black sigatoka）传入巴西圣保罗州里贝拉谷（Vale do Ribeira）地区的商业化香蕉种植园，为避免叶片脱落，针对易感品种的该病害严重度监测与化学防治工作已愈发频繁。本研究针对‘普拉塔普通（Prata Comum）’香蕉果实，模拟了该病害引发的落叶对其产量与品质的影响，分析因素包括果串（bunch）形成期以及果实在果串中的着生位置。本试验采用完全随机设计，设置2×11析因方案（factorial scheme，果串形成期×花期叶片数）：设置两个果串形成期，花期叶片数梯度覆盖6~16片（共11个水平），每组处理设置6次重复。试验组1的花期为2013年4月15日，试验组2的花期为2014年1月7日；尽管试验组1的果串重量更高，但试验组2的日均最高温、日均最低温、降水量与辐射量均更高。无论果串形成期如何，花期叶片数均会影响果串重量，其范围为18~23 kg/株。落叶会影响果串第一果梳（hand）与最后一果梳的果实大小，但不会因果实在果串中的着生位置以及果实理化特性导致果实大小出现变异。