Evaluation of pomological traits of pear decline-resistant rootstocks

Twenty pear rootstock genotypes were examined for their pear decline resistance and their pomological traits in a six years field trial. All rootstock selections were grafted with the susceptible cultivar Williams followed by graft-inoculation with a severe strain of ‘Candidatus Phytoplasma pyri’ prior plantation. Seven years post inoculation all surviving trees were positive in PCR analyses. The concentration of the phytoplasmas was determined by quantitative real-time PCR and ranged from 3x10⁶ to 6x10⁷ phytoplasma cells per gram of phloem tissue. Among the grafted rootstock genotypes clear differences in mortality, symptom expression and pomological performance were observed. Pear decline-tolerant rootstocks with promising pomological traits were selected for further evaluation.