Detection of a hypersensitive reaction in the chestnut hybrid ‘Bouche de Bétizac’ infested by Dryocosmus kuriphilus Yasumatsu

The purpose of the study was the identification of the mechanisms of resistance to Dryocosmus kuriphilus Yasumatsu in the hybrid-resistant cultivar ‘Bouche de Bétizac’ (Castanea sativa × Castanea crenata). Larvae and eggs of the insect are found in the buds of this cultivar at the end of winter, but there is no gall development after budburst. The hypothesis of the presence of a hypersensitive reaction (HR) in the buds was tested using diaminobenzidine (DAB) to detect H2O2 and by Real Time PCR (RT-PCR) to evaluate the expression of a germin-like protein gene. HR in plants is elicited by the production of reactive oxygen compounds, such as H2O2, and results in the programmed cell death. The DAB test was applied to buds of ‘Bouche de Bétizac’ and of the susceptible cultivar ‘Madonna‘ (C. sativa) at different stages of budburst. The DAB staining produced brown areas in the swelling buds of ‘Bouche de Bétizac’, indicating the presence of H2O2. On the contrary, all uninfested buds, as well as the infested buds of ‘Madonna‘, appeared whitish. Papers report that germin and germin-like proteins (GLP) with oxalate oxidase activity are discrete markers of stress-responsive gene products. A strong expression of the chestnut GLP gene was detected by RT-PCR at bud swelling in infested ‘Bouche de Bétizac’ buds but not in ‘Madonna’ ones. The results support the hypothesis of the occurrence of an HR in ‘Bouche de Bétizac‘ as response to the cynipid infestation, resulting in cell and larvae death.

► The response to Dryocosmus kuriphilus was studied in a resistant chestnut cultivar. ► DAB test was used to detect H2O2 in infested buds of the resistant cultivar. ► RT-PCR of a germin-like protein (GLP) was used to confirm the synthesis of H2O2. ► H2O2 presence and enhanced GLP gene expression were related to resistance response. ► Resistance in cultivar ‘Bouche de Bétizac’ is due to a hypersensitive reaction.