The occurrence of <i>Ilarviruses</i> in Latvian fruit orchards

Abstract

In order to study the occurrence of ilarviruses in fruit orchards in Latvia the samples from apple, pear and Prunus trees from commercial orchards and varietal collections were collected during spring 2007 and 2008. Polyclonal antibodies were used for DAS ELISA test for large-scale screening. In Total 890 samples from apple, 252 samples from pear and 655 samples from Prunus spp. were tested for the occurrence of fruit tree ilarviruses – ApMV, PDV and PNRSV. The screening results showed that all tested ilarviruses were present in the fruit orchards. ApMV was detected in 2.1% of the tested apple samples and in 1.8% of the plum samples, but it was not detected in pears. In Prunus spp. PNRSV was detected in 13.6% and PDV in 11.6% of samples. Mixed infections of ilarviruses were detected in 4% of the tested Prunus spp. samples of which 2% was PNRSV in combination with PDV. The plant samples from apple and pear trees were tested for ApMV infection also by RT-PCR and compared with data obtained by DAS ELISA. The RT-PCR results showed that 22% and 20.2% of tested apple and pear trees are infected with ApMV, respectively. The occurrence of ilarviruses in the tested plants varied greatly among the cultivars. The commonly grown cultivars such as ‘Ausma’, ‘Rubin’, ‘Kursa’, ‘Bere Kievskaya’, ‘Perdrigon’, ‘Mirabelle de Nancy’ and ‘Skoroplodnaya’ were highly infected. Since a certification system for planting material is not established in the country, there is very high risk for continuous spread of these viruses in the orchards. Similarly, as showed for ApMV, also PNRSV and PDV possibly are more widely spread than detected with preliminary screening by DAS ELISA. The study should be continued and other test methods, such as RT-PCR, used. The obtained data indicate a great need for the establishment of a certification system for fruit tree propagation.

Keywords: ApMV, apple, ELISA, PDV, pear, PNRSV, Prunus, RT-PCR