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Abstract
Three aphid species Aphis craccivora, Myzus persicae and Aphis gossypii were found on soybean plants grown at Giza region during seasons of 2001 and 2002 with a low average number in soybean field. Five wild plant species, Convolvulus arvensis, Euphorbia spp., Solanum nigrum, Amaranthus spp. and Portulaca oleraceae are considered to be reservoirs for the three different aphid species and soybean mosaic virus (SMV). Seasonal abundance of the different aphid species on wild plants associated with soybean in the field showed that, M. persicae gave the highest recorded number 71.42 individuals/plant on Convolvulus arvensis, while A. craccivora recorded 76.28 individuals/plant on Portulaca oleraceae and A. gossypii gave 26.77 individuals/plant on Portulaca oleraceae. Soybean mosaic virus was isolated from naturally infected soybean leaves in the field at Giza region, Egypt. The virus was sap, aphid and seed transmissible, showed inclusion bodies as a pinwheel form in the cytoplasm and success of grafting. Virus-vector relations showing high efficiency of A.craccivora (76.19%) and its nymphs (71.87%) in transmission of soybean mosaic virus (SMV). Acquisition access time (AAT) and inoculation access time (IAT) found to be 1 and 30 min. as a rate of soybean mosaic virus transmission, respectively while newly-borne progeny was virus free. The virus has different host range and shows development of symptoms started by mild, severe mosaic while ended by reduction in leaflet size and malformation of leaves. TIP is 60°C, DEP is and LIV is 60 hours for soybean mosaic virus. SMV/RNA was successfully detected in infected soybean plants and in Myzus persicae by RT-PCR. Dot blot immunoassay and dot blot hybridization detected the presence of viral infections in the collected tissues of soybean plants. PCR product of SMV/CP gene was ligated and cloned into a PGEM-T-Easy cloning vector.
The recombinant plasmids were validated by PCR where clones contained the right CP gene inserted with the correct size. Partial nucleotide sequencing showed relations, alignment and homology between the soybean mosaic virus (Egyptian isolate) and other isolates. Natural infection of soybean plant with soybean mosaic virus (SMV) in the field led to yield loss. This can be observed by the decreasing of yield parameters in infected soybean plants compared to the healthy ones.