MINERAL NUTRITION OF PEAR AND APRICOT TREES CULTIVATED IN SOUTHERN ITALY AREA DAMAGED BY PHYTOPLASMA MICROORGANISMS

Abstract

The aim of this research was to investigate the relationship among leaf mineral nutrition, soil chemical fertility, presence of phytoplasma in fruit trees and susceptibility of the plant to become infected. In the experimental farm, pear and apricot orchards were cultivated, in separate areas far 30 metres each other and since 1997 they resulted respectively infected by 'Candidatus Phytoplasma pyri' and by 'Candidatus Phytoplasma prunorum'. In 1999 whole collections of these two species had been eradicated and substituted with new plants of the same species. Four pear plants had been selected in the old collection and had been covered by anti-aphid tissue. These pear plants (three infected by the phytoplasma and one healthy) and four healthy apricot plants were analysed for the presence of phytoplasma, for the nutritional status of leaves as well as for the soil chemical fertility. This study was carried out in two years, from May 2006 to September 2007. The results showed a Fe/Mn ratio unbalanced in the pear infected plants compared with the pear healthy ones. The pear leaves of the healthy plant didn't show any disequilibrium, while those of the infected plants showed the unbalanced ratio Fe/Mn either when the molecular test for phytoplasma detection was still negative. The apricot leaves, always resulted free from phytoplasmas, showed a K/Mg imbalance.