Seasonal detection of pear decline phytoplasma by nested-PCR in different pear cultivars

Abstract

Seasonal detection of pear decline phytoplasma was studied in three pear cultivars: Bartlett, Limonera and Blanquilla. Samples from 43 infected trees were collected monthly over 2 years and analysed by nested PCR. The three cultivars each showed a different pattern of phytoplasma detection. The maximum detection rate of pear decline phytoplasma occurred in December in the three orchards, and it remained high throughout the winter months. In spring, when new buds appeared and sap was produced, the detection rate decreased. Leaf midribs, buds and stems were compared to determine which sample was more reliable for phytoplasma detection. The best indicators were stems. The presence of phytoplasma in sieve tubes during the dormant season was determined by grafting. The results suggest that phytoplasmas could over-winter in shoots, with the implication that vegetative propagation during this period could also disseminate the disease.