Susceptibility to Dryocosmus kuriphilus Yasumatsu and molecular analyses of chestnut genotypes

Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae) is a serious pest of chestnut trees; it lays eggs into dormant buds and, in the following year, causes the development of galls on leaves, sprouts and inflorescences, due to the feeding activitity of larvae. The galls have a negative effect both on growth and yield of the tree. In 8 years of observations the susceptibility to the cynipid was evaluated under controlled conditions and assessed for some 100 cultivars and selections, including Castanea sativa and hybrid genotypes. Complete resistance to D. kuriphilus was firstly found in the hybrid ‘Bouche de Bétizac’ (C. sativa X C. crenata) and more recently in C. sativa cultivars and wild individuals. In the years 2008, 2009 and 2010, an F1 offspring was created by crossing between the euro-japanese hybrid ‘Bouche de Bétizac’ and the C. sativa cultivar ‘Madonna’, susceptible to the insect, in order to study the reaction of the chestnut tree to the cynipid infestation. The nucleic acids extracted from this material were used for different analyses: the costruction of a genetic map of chestnut, the identification of the molecular bases of the chestnut resistance to the cynipid and the isolation of genes involved in the response to the insect in susceptible genotypes.