Isolation of Cryphonechia parasitica from Cankers on Chestnut Trees in ]Korea

Abstract

A total of 672 Cryphonectria parasitica was isolated from 2,536 blight lesions on chestnut twigs, which were collected from major chestnut plantations all over Korea. Isolation rates of each province ranged from 13.5% in Jeonbuk-ds to 37.4% in Gyeongnam-do, with an average rate of 25.6%. The isolates were classified into six groups according to color and shape of colony on PDA: smooth margin (S), irregular margin (I), yellow to brown (Y), white (W), and white with yellow center (C). Among these groups, IY was the most abundant with an isolation rate of 65%. On the other hand, SW, SC, IW, and SY were quite rare, with isolation rates ranging from 1.5% to 5.8%. When the 672 isolates were inoculated on the chestnut twigs,380 isolates (56.5%) caused lesions larger than the standard virulent isolate EPISS-2, while 158 isolates (23.4%) caused smaller lesions than the standard hypovirulent isolate UEP-1. However, 87.4% of the isolates belonged to the virulent group and only 12.6% belonged to the hypovirulent group based on Bavendamm test. In the provinces of Jeonnam-do, Jeonbuk-do, and Gyeongnamdo, which have high density of chestnut trees, the rates of hypovirulent-like isolates were over 20%.