Leaf samples from Crotalaria paulinea showing mosaic were collected in the city of São Luiz, MA and sent to the Plant Virus Laboratory at the UFC. The leaf samples were tested by indirect enzyme-linked immunosorbent assay (Elisa) against antisera specific to Cowpea aphid-borne mosaic virus (CABMV) and Cucumber mosaic virus (CMV) and by gel double-diffusion against antiserum to Cowpea severe mosaic virus (CPSMV). The samples reacted only with the antiserum to CPSMV indicating that C. paulinea is one more natural host of the virus. Leaf extracts from infected C. paulinea were mechanically inoculated in cowpea (Vigna unguiculata subsp. unguiculata) plants maintained in greenhouse. Ten days after inoculation, the plants started to exhibit mosaic and the presence of CPSMV was confirmed by serology. In a host range study involving eight plant species, the CPSMV isolate obtained from C. paulinea (CPSMV-Cp) infected only cowpea cultivars. The results of RT-PCR revealed a band in the agarose gel of 594 pb for CPSMV-Cp similar to those of other CPSMV isolates. The CPSMV-Cp was increased in cowpea cv. Pitiuba and purified by clarification using n-butanol, virus particle precipitation with polyethylene glycol (PEG) and ultra centrifugation. The purified virus preparation presented an ultraviolet light absorption spectrum typical of nucleoprotein, with a ratio A260/A280 equal to 1.7. A White New Zealand rabbit immunized with the purified virus preparation produced polyclonal antiserum reactive to CPSMV in agar double-diffusion. This is the first report about natural infection of C. paulinea by CPSMV.
Comovirus; CPSMV; cowpea; Vigna unguiculata
