Virus diseases of Queensland strawberries and the epidemiological effects of the strawberry runner approval scheme

Abstract

Four viruses infecting strawberry cvs. in Qd, were identified. Tobacco streak virus was isolated mechanically and reinoculated to strawberry plants. It was identified serologically, morphologically and by host range. Strawberry mild yellow edge, strawberry mottle and strawberry latent A viruses were identified by indicator reactions. SMV was readily transmitted by both Chaetosiphon fragaefolii and Aphis gossypii but no experimental aphid transmission of SMYEV was obtained. No virus particles were seen by electron microscope examination of thin sections of material infected by SMV, SMYEV or SLAV. The reactions of Duchesnea indica to inoculation with SMV, SMYEV and TSV were investigated. This naturalised sp. is a poor host of these viruses and would have little epidemiological importance. Examination of symptoms on 7 indicators showed that the Fragaria vesca clones were better indicators than F. virginiana clones for these viruses. Severe symptoms were produced on plants of the main commercial cv. (Redlands Crimson) by artificial virus complexes of SMYEV + SMV and TSV + SMV, but the latter was not severe in the chronic phase. The virtual eradication of strawberry viruses from commercial plantings in Qd, is attributed to distribution of uninfected material and a reduction in vector populations.<new para>ADDITIONAL ABSTRACT:<new para>Four viruses infecting strawberries were identified, namely tobacco streak virus (TSV), strawberry mild yellow edge (MYEV), strawberry mottle virus (SMV) and strawberry latent A virus (SLAV). SMV was readily transmitted by Chaetosiphon fragaefolii and Aphis gossypii but MYEV could not be transmitted experimentally. Fragaria vesca clones were better indicators than F. virginiana clones for these 4 viruses. It was concluded that the virtual eradication of strawberry viruses from commercial plantings could be attributed to distribution of healthy planting material and a reduction in vector populations.<new para>ADDITIONAL ABSTRACT:<new para>Of 4 viruses identified in strawberry in Queensland, strawberry mottle virus (SMV) was readily transmitted by Chaetosiphon fragaefolii (Ckll.) and Aphis gossypii Glov.; both aphids were present on strawberry in the field. The ornamental Duchesnea indica, which is widely grown and occurs as a naturalised weed, was a poor acquisition source for SMV by the aphids. C. fragaefolii has almost disappeared from commercial strawberry crops in Queensland in the past 15 years, and it is suggested that transmission of SMV within field plantings of the first release of the Redlands Crimson cultivar was probably by A. gossypii. The virtual eradication of strawberry viruses from commercial plantings in Queensland is attributed to the distribution of uninfected material and a reduction in aphid vector populations.