Location of prunus necrotic ringspot ilarvirus within pollen grains of infected nectarine trees: evidence from RT-PCR, dot-blot and in situ hybridisation

Prunus necrotic ringspot Ilarvirus (PNRSV) is a pollen and seed-borne ilarv irus affecting most Prunus spp. The location of the virus in infected necta rine pollen grains was investigated by molecular hybridisation, RT-PCR and in situ hybridisation. The first two approaches revealed an internal locati on of the virus. In situ hybridisation demonstrated the virus in the bicell ular pollen grain, where it was present in the cytoplasm of the vegetative cell but not in the generative cell. This result seems to indicate that the sperm cells, formed by the mitosis of the generative cell, are not involve d in virus transmission to seed. Other possible mechanisms are discussed.