Abstract
The psyllid Cacopsylla melanoneura is considered one of the vectors of ‘Candidatus Phytoplasma mali’, the causal agent of apple proliferation disease. In Northern Italy, overwintered C. melanoneura adults reach apple and hawthorn around the end of January. Nymph development takes place between March and the end of April. The new generation adults migrate onto conifers around mid-June and come back to the host plant species after overwintering. In this study we investigated behavioural differences, genetic differentiation and gene flow between samples of C. melanoneura collected from the two different host plants. Further analyses were performed on some samples collected from conifers. To assess the ecological differences, host-switching experiments were conducted on C. melanoneura samples collected from apple and hawthorn. Furthermore, the genetic structure of the samples was studied by genotyping microsatellite markers. The examined C. melanoneura samples performed better on their native host plant species. This was verified in terms of oviposition and development of the offspring. Data resulting from microsatellite analysis indicated a low, but statistically significant difference between collected-from-apple and hawthorn samples. In conclusion, both ecological and genetic results indicate a differentiation between C. melanoneura samples associated with the two host plants.
Highlights
The agronomic importance of the Hemiptera genus Cacopsylla is due to the role that several of its species play in the transmission of phytoplasma diseases belonging to the apple proliferation cluster, including ‘Candidatus Phytoplasma mali’, ‘Ca. P. pyri’ and ‘Ca. P. prunorum’ [1]
By definition, ‘‘host races’’ are genetically differentiated, sympatric populations of parasites associated with different hosts plant species, on which they feed and reproduce, and between which there is appreciable gene flow [42]
A differentiation between the two groups, which are linked to different host plants for their development and reproduction, was suggested by the genetic analyses performed on the different samples
Summary
The agronomic importance of the Hemiptera genus Cacopsylla is due to the role that several of its species play in the transmission of phytoplasma diseases belonging to the apple proliferation cluster, including ‘Candidatus Phytoplasma mali’, ‘Ca. P. pyri’ and ‘Ca. P. prunorum’ [1]. Cacopsylla melanoneura (Forster), one of the most common psyllids in Italian apple orchards, is known as a vector of AP in Northwestern Italy [3], while it was shown not to transmit this disease in Germany and neighbouring countries [4]. This univoltine species is linked to some Rosaceae Maloideae, such as Crataegus, Malus and Pyrus spp. The adults of the generation (emigrants) leave the orchard around mid-June and move to the overwintering host plants. Conifers have been reported to be shelter plants for the aestivation and overwintering of the new generation [7,8,9]
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