Measurements of chlorophyll fluorescence as an auxiliary method in estimating susceptibility of cultivated hazel (Corylus L.) for filbert aphid (Myzocallis coryli goetze)

Abstract

The influence of aphid feeding on chlorophyll a fluorescence in the leaves of four cultivated hazel cultivars, with different levels of resistance to filbert aphid (Myzocallis coryli Goetze), was studied. The maximum effect of photosystem reaction measured on dark-adapted hazel leaves (Fv/Fm parameter) and maximum efficiency of photon energy PAR conversion to chemical energy in light conditions (Y parameter) were estimated twice, in the leaves of four hazel cultivars with different levels of resistance to filbert aphid, using a fluorometer PAM- 2000 by Walz GmbH - Germany. The analysis of changes of these parameters showed that aphid feeding caused a reaction in all tested cultivars. The most visible reduction of the Fv/Fm and Y values as a result of aphid feeding was observed in the cultivars 'Cud z Bollwiller' and 'Olbrzymi z Halle', numerously colonized by aphids. A smaller number of aphids found on the leaves of more resistant cultivars - 'Kataloński' and 'Lamberta Biały', caused a weaker response of plants and a smaller decline in the value of this parameter. 'Cud z Bollwiller' cultivar showed higher tolerance than other tested cultivars to stress caused by the feeding of sucking insects. The Fv/Fm and Y parameters can be regarded as reliable indexes useful in diagnosing susceptibility of hazel cultivars to aphids, helpful in determining, for example, harmfulness thresholds.