AN INOCULATION METHOD FOR EARLY ASSESSMEN T OF LARCH RESISTANCE TO LACHNELLULA WILLKOMMII

Efficiency of inoculation with mycelium and ascospores was compared on 4-13-year-old Larix decidua. Only mycelium induced high infection rat es. Mycelial inoculum was contained in colonized sorghum-straw pieces and was introduced in 1 mm diameter holes drilled through the bark in April/May. The main infection was detectable as early as 18 months aft er inoculation and infection rate increased only until the 28th month after inoculation. The susceptibility of the branches did not depend o n their age, their position in the trees, the age of inoculated shoots or the management of the trees. Susceptibility was even for the 1-2-y r-old parts of the stems and branches but the oldest parts of the stem s were less susceptible. The inoculation method was effective for dete cting differences in susceptibility among trees. One seedling from the Alps, and clone 3001-00035, which is the mother of resistant hybrids, were the least susceptible.