The influence of horse-chestnut grafting on characteristics of resistance to chestnut leaf miner Cameraria ohridella Deschka & Dimić

Abstract

A number of forms of Aesculus hippocastanum L. are resistant to chestnut leaf miner (CLM) Cameraria ohridella Deschka and Dimić. Here, we studied the influence of grafting scions and rootstock of such forms on persistence of that resistance. Obtaining seedling material by grafting is effective in 60-70 % of cases. Grafted horse-chestnut scions resistant to CLM on two-year old rootstock of vulnerable forms were more susceptible to the pest. Leaves of grafted plants demonstrate signs of deformations and damage associated with CLM for the first two years of vegetation after grafting. CLM infection of plants is accompanied with the increasing concentrations of chlorophylls a and b, and carotenoids. The content of total phenols and catechins also increases in infected leaves. This indicates a restructuring of the secondary metabolism associated with the synthesis of phenolic compounds and terpenoids. Such partial damage together with the increased content of condensed tannins in leaves of CLM-resistant form of horse chestnut confirms the inability of tannins to protect the plant from CLM. It is shown that CLM caterpillars can hydrolyze phenols, in particular proanthocyanidins. Based on our experimental data, phenols are thought to be fermented by intestinal enterobacteria of CLM caterpillars.