Occurrence of <i>Little cherry virus</i>-1 on <i>Prunus</i> species in the State of Baden- Württemberg, Germany

Abstract

A survey on Little cherry virus-1 (LChV-1) on several Prunus species has been performed at four different sites in the
State of Baden-Württemberg (BW) between 2003 to 2006. These included a state-run growing site for prebasic and
basic material, two commercial nurseries for certified scion or rootstock production and an orchard for cultivar verification testing. A total of 63 varieties of sweet, sour and ornamental cherries belonging to four Prunus species (P. avium L., P. cerasus L., P. serrulata Lindl., P. subhirtella Miq.) as well as six types of Prunus-rootstocks were tested. Ten of the 44 P. avium and one of the two P. serrulata varieties were partly or totally infected, whereas the P. cerasus and P. subhirtella varieties and the Prunus-rootstocks gave negative results. None of the infected plants showed distinctive disease symptoms.

Dispersal of LChV-1 from the infested P. avium trees was not detected in the orchard for cultivar verification testing after a period of five years. A natural dispersal from varieties infected for about 10 years in a nursery for scion production to adjacent healthy varieties was observed only in single cases. There was no indication of any involvement of animal vectors.

Testing of randomly sampled material from some trees of P. avium and P. serrulata for scion production proved a homogenous distribution of the virus in shoots in autumn.

At the moment studies are conducted to verify the responses of young trees of the sweet cherry variety ‘Regina’ to experimental inoculation with either LChV-1 or LChV-2 or a mixture of both viruses. First year results indicate that - in complete contrast to LChV-2 - no adverse effects of LChV-1 on the fruit yield, single fruit weight, fruit size and trunk circumference were observed. In mixed infections, LChV-1 seems to attenuate the adverse effects of LChV-2 on fruit yield and trunk circumference.

Keywords: Little cherry virus-1, Little cherry virus-2, Baden-Württemberg, Prunus species, varieties, rootstocks, certification, dispersal, distribution, effects