2023 Volume 22 Issue 2 Pages 125-132
Selection of suitable rootstock species which can improve the freezing tolerance of Japanese chestnut (Castanea crenata Sieb. et Zucc.) cultivars has been required in recent years, because the incidence of freezing injuries has been marked in newly established orchards. The three objectives of the present study were as follows: 1, selection of freezing-tolerant rootstock strain that grafts compatibly with Japanese chestnut cultivars, 2, establishment of layering propagation, 3, explanation of mechanisms of freezing-tolerant rootstocks. Among the 12 rootstock strains, graft compatibility of the ‘Ginyose’ seedling with the ‘Tsukuba’ scion was high (95%), whereas that of the Chinese chestnut seedlings was low (4–37%). However, ‘Tsukuba’ with the Chinese chestnut strain “Jiangxi” showed a high survival rate under severe environmental conditions where the mortality rate of trees grafted with other rootstock species reached 50–100%. Moreover, layering propagation could be applied to the “Jiangxi” No. 345 strain because the rooting rate reached 64.7%. The “Jiangxi” No. 345 strain showed graft compatibility with the ‘Tsukuba’ scion, and 41.2% of the nursery plants could be used for planting. The ‘Tsukuba’ with “Jiangxi” No. 345 rootstock showed a low shoot water content and high freezing tolerance of buds during winter compared with the plant plus conventional rootstocks. Consequently, the incidence of freezing injury in the field was decreased using “Jiangxi” No. 345, rootstock. These results indicate that “Jiangxi” No. 345 which can be propagated by layering, has a high potential to become a new rootstock strain for Japanese chestnut, because it can improve freezing tolerance by reducing the branch water content during winter.
