Monitoring the occurrence of 'Candidatus Phytoplasma pyri' depending on the pear cultivars in the Czech Republic

In Europe, pear orchards are increasingly affected by the pathogen ‘Candidatus phytoplasma pyri’, the causal agent of pear decline. The situation in the Czech Republic is very similar, where the intensity of infection depends on the cultivar, the origin of the planting material, the growing system and the locality. In 2016 the pear growing area was 710 ha with the production of 6,643 t with the average yield 10.54 t ha^‑1. In the framework of the experiment, the largest pear producers in four main growing regions in the Czech Republic: Northern Bohemia, Eastern Bohemia, South and Western Bohemia and Moravia, were monitored. The area of pear orchards at monitored producers ranged from 66 to 5 ha. The most planted cultivars of the world assortment were: ‘Williams’ (‘Bartlett’), ‘Conference’, ‘Clapp’s Favourite’, ‘Beurré Bosc’, ‘Packham’s Triumph’, ‘Hortensia^®’, ‘Alexander Lucas’. The Czech cultivars were represented by: ‘Bohemica’, ‘Nitra’, ‘Nela’, ‘Erika’. Preliminarily tested samples showed high proportions of infected trees for cultivars ‘Hortenzia^®’ (38.5%), ‘Packham’s Triumph’ (50.0%) and ‘Williams’ (41.7%) grown on quince rootstocks, while less proportion of infected trees were shown in the case of ‘Alexander Lucas’ (42.5%), ‘Nela’ (60.0%), and ‘Nitra’ (44.0%). According to the results, a higher number of trees grafted on pear seedling (68.8%) were infected than on quince rootstocks (47.1%).