Screening resistance to chestnut blight in young chestnut trees derived from Castanea sativa × C. crenata hybrids

Abstract

In 2010, 2011 and 2012 four trials were carried out to prove a reliability of the new screening method for resistance to chestnut blight caused by Cryphonectria parasitica. In the selected trees of hybrid origin (C. sativa × C. crenata)) 10 cm long cut-branch sections were inoculated with mycelia of three virulent isolates and one hypovirulent isolate (in two last trials) and cultivated for 7 days in the dark at 25 °C with 95% humidity. Then the bark of branch segments was peeled off and the size of necrotic lesions formed on the wood tissue around the inoculation place was measured. The size of necrotic areas varied by sampling date, type of fungus strains and tested trees. In all three summer trials necrotic lesions were larger than lesions in a spring trial of 2011, in which still dormant stem sections were used. Unlike the summer trials in the spring trial higher differences in the size of necrotic lesions among tested trees and among used virulent strains were observed. In the spring trial interactions between tested trees and fungal isolates were not so frequent like in summer trials where more trees exhibited different response to the same virulent strain. Majority of trees showed different susceptibility in particular trials. Observed high variation of reactions of tested trees to both virulent and hypovirulent isolates has pointed at the need to prove other screening methods, and to find such one, that would be highly effective to reveal an inherited resistance and/or a lower degree of susceptibility to chestnut blight.