RELATIONSHIP BETWEEN THE RESISTANCE OF HAZELNUT CULTIVARS TO THE HAZELNUT WEEVIL AND THE CONTENT OF SUGARS, AMINO ACIDS, AND PHENOIS IN THE ENDOCARP TISSUE OF GROWING NUTS

In the course of 10 year investigations /1981–1990/ considerable differences were found in the resistance of 24 hazelnut cultivars to hazelnut weevil. The resistance was determined on the basis of the percentage of nuts damaged by the weevil larvae, using a 6 class scale, from class 1 - resistant, to class 6 - very susceptible cultivars. A close positive correlation was found between the class of cultivar resistance and the content of sugars and free amino acids in the endocarp tissue of growing nuts, significant at 1% and 5% level, respectively. A negative correlation was found between the class of resistance and the content of total phenols in the same tissue, significant at 1% level. A close relationship was also found between the class of resistance and the frequency of beetles feeding on growing nuts during the oviposition period /1st half of July/. The results suggest that the chemical composition of the parenchymatous white endocarp tissue which is the main food for the pest beetles during the oviposition period, is one of the factors affecting the resistance of hazelnut cultivars to the hazelnut weevil.