Variation in fruit traits and infestation ratios in natural sweet chestnut (Castanea sativa) populations under chestnut weevil (Curculio elephas) damage

Abstract

Sweet chestnut (Castanea sativa Mill.) is one of the most important species in agro-forestry and horticulture. Turkey is an important C. sativa gene centre and fruit production region. The present study aimed to measure the variations in fruit width, length, thickness and weight in four different natural C. sativa populations in Turkey and determine the loss of fruit traits due to damage by chestnut weevil (Curculio elephas (Gyllenhal, 1836)) (Coleoptera: Curculionidae). Fruits were collected from four populations (Istanbul-Bahcekoy, canakkale-Bayramic, Balikesir- Erdek and Bursa-Uludag) of phenotypically healthy sweet chestnut trees, measurements were taken, and the fruits were classified into those damaged by C. elephas and those not. Analysis revealed significant differences among and within the populations in all fruit traits, and between the sound and damaged fruits, with the average fruit width, length, thickness and weight being 24.8 mm, 23.1 mm, 15.3 mm and 3.4 g, respectively. Bursa-Uludag population had the highest healthy fruit ratio (70%), with some individuals in the population yielding healthy fruits at ratios > 90%. In the Balikesir-Erdek population, however, where the percentage of damaged fruits was the highest (54%), it was determined that some trees suffered more than 90% damage in contrast to the Bursa-Uludag population. In the fruits infested by C. elephas, the approximate percentages of loss in fruit width, length, thickness and weight were 6, 4, 7 and 30%, respectively. The fruit weight loss percentages varied between 25% and 32% among the populations.