Experimental transmission trials by <i>Cacopsylla pyri</i>, collected from Pear Decline infected orchards in Turkey

Abstract

A study was carried out on the experimental transmission efficiency of the Pear Decline (PD) phytoplasma by Cacopsylla pyri (L.) C. pyri were collected from naturally infected orchards in Bursa province (Plots B1 and B2) and a non-infected orchard in the Hatay-Antakya province (Plot A) of Turkey. C. pyri adults captured from infected orchards were placed directly onto healthy periwinkle plants (Catharanthus roseus), whereas the C. pyri from plot A were allowed to feed first on infected pear for two weeks, then transferred to healthy periwinkle plants. Groups of five psyllids per plant were used for transmissison tests and the study was replicated three times. The presence of ‘Candidatus Phytoplasma pyri’ in psyllids and C. roseus plants was checked by nested PCR using P1/P7 and U3/U5 primer pairs. Although C. pyri have a limited host range they were able to survive up to 20 days on periwinkle plants. Insects collected from Bursa province survived 16-20 days whereas insects from Antakya survived 7-12 days on periwinkle plants. Symptoms consisted of yellowing or clearing of the veins in newly infected leaves, and shortening of the internodes of the main stem. The infected plants remained stunted and with small flowers. Results based on the RFLP analysis of infected plants exposed to psyllids from plot B1and B2 indicated that the experimental infection rate of periwinkle plants and psyllids was 33.3% and 16.6%, respectively. No infected periwinkle was found in plants exposed to psyllids from plot A, but the psyllids used for experimental transmission experiments were 33.3 % infected. Transmission trials under controlled conditions showed the capability of C. pyri to transmit PD from infected pears to healthy periwinkles and confirmed their potential as vectors of Ca. P. pyri in Turkey.

Keywords: Candidatus Phytoplasma pyri, pear psyllid, transmission efficiency