Assessing the susceptibility levels of chestnut cultivars/genotypes to Asian chestnut gall wasp (Dryocosmus kuriphilus Yasumatsu)

Abstract

The Asian chestnut gall wasp Dryocosmus kuriphilus is a major insect pest affecting chestnut trees worldwide. Due to the galls that it creates on shoots and leaves, this pest prevents shoot development and blooming and decreases the fruit yield. In Türkiye, this pest was first seen in Gacık village of Yalova province in the year 2014. Today, it is seen in orchards and forests in different provinces of Marmara, Aegean, and Black Sea regions. The medium- and long-term control of this pest can be improved by making use of resistant or less-susceptible cultivars and hybrid clones. The susceptibility levels of our cultivars to this pest are not known. For this purpose, by using three infestation indicators, the susceptibility to Asian chestnut gall wasp (ACGW) of 3 hybrids (Castanea sativa x Castanea crenate) and 20 cultivars/genotypes (C. sativa), which came to the forefront via selection studies, were assessed for five years (2017-2021). The susceptibility to ACGW varied between the tested genotypes/cultivars and, since no gall development was observed in ‘YD-1’, ‘Tülü’, and ‘Ertan’ cultivars of C. sativa species, they were determined to be completely resistant to ACGW. Furthermore, the numbers of ACGW eggs on the buds of cultivars were recorded and it was found that ACGW laid eggs on the buds of all the cultivars. In microscopic analyses, it was revealed that the resistance originated from the prevention of larva development within the bud. The finding that resistant cultivars belong to C. sativa species is thought to be important for future genetic breeding programs.