Occurrence of the strawberry mottle virus in São Paulo

The ocurrence of virus strains similar to those of the strawberry mottle virus has been recorded in several strawberry plantings in the state of São Paulo. Old, standard varieties are symptomless carriers and are usually 100 per cent infected. Some new clones, representing various crosses, were partly infected after a Few plantings in the field. The symptoms induced by die virus on Fragaria uesca seedlings were vein clearing, crinkling, and stunting. Most of the virus isolates seemed to resemble curly dwarf. Studies on host range carried out by means of the vector gave mostly negative results, but symptoms were obtained on Cassia occidentalis, Chenopodium quinoa, Leonotis nepaetifolia, and Leonorus sibiricus Although this happened when inoculations were made with different sources of the strawberry mottle virus, it cannot be stated with certainty that the symptoms obtained on these four species were really caused by the mottle virus, since it was possible that the original sources contained another virus. The strawberry mottle virus was transmitted efficiently by Pentatrichopus fragaefolii and only occasionally by Aphis gossypii. Seed transmission was negative. Tests on mechanical inoculation were also negative. However, the virus obtained on Chenopodium quinoa plants by means of the vector could be transmitted mechanically to seedlings of the same species, but not to Fragaria vesca. A local species of Cuscuta did not transmit the mottle virus and transmission with leaf scions grafted on leaves was generally low because of poor take. Pentatrichopus fragaefolii became infective after feeding 30 minutes on the virus source. Its efficiency apparently increased as the feeding time on the virus source increased. Viruliferous vectors were able to infect healthy plants in 15 minutes. Virus was retained by viruliferous vectors after feeding on a healthy plant for one hour. After a 6-hour feeding period the insects lost infectivity.