15 YEARS OF OBSERVATIONS ON THE AGRONOMIC BEHAVIOR OF 7 HEAT-TREATED PEAR TREE CULTIVARS

Performance of heat-treated clones of seven pear cultivars in a contam inated orchard were observed over 15 years and compared with non-treat ed clones (virus infected) of the same cultivars. The heat-treated clo nes were more successful in budding, had a 10% increase in vigour, 15- 50% better cropping depending on the cultivar. The yield per tree size varied between the heat-treated and non-treated from 3 to 16 kg per t ree per centimetre trunk girth. Only ''General Leclerc'' proved an exc eption: the treatment seemed to have brought about the appearance of a ''variant'' which flowered later and had a smaller yield. Throughout the 15 year study period we did not observe any natural viral contamin ation in the orchard.