Epidemiology of soybean bud proliferation and seed pod abortion disease in Iran

Symptoms of bud proliferation and aborted seed pods were observed in Iranian soybean fields in Golestan and Mazandaran provinces. Symptomatic soybean plants, possible insect vectors, and alternative plant host species were collected to verify the presence of possible pathogens. Symptomatic and asymptomatic soybean and herbaceous plant samples were subjected to ELISA for virus detection and all samples were subjected to nested PCR amplification of phytoplasma 16 S ribosomal RNA gene followed by sequence and phylogenetic analysis. A 'Candidatus Phytoplasma trifolii' strain was detected in the symptomatic soybean samples and in samples of willow and pampas grass. Some viruses were also detected in some the tested soybean samples. Biological assays such as insect and graft transmission were performed. Experimental infection of healthy soybean plants with symptomatic soybean shoots resulted in bud proliferation and seed pods abortion symptoms 8 weeks after grafting. The Hemiptera Creontiades pallidus known also as cotton shredder bug, transmitted 'Ca. P. trifolii' to healthy soybean plants under insect proof conditions. The reported identification of the phytoplasmas associated with this soybean disease, of their reservoir or alternative host plants and of an insect vector will help in the development of more effective strategies to manage this disease under the Iranian field conditions.