Resistance to Bean pod mottle virus in transgenic soybean lines expressingthe capsid polyprotein

Transgenic fertile soybean plants were generated from somatic embryos of so ybean (Glycine max) cv. Jack transformed via particle bombardment with the capsid polyprotein (pCP) gene of Bean pod mottle virus (BPMV). The plant tr ansformation vector (pHIG/BPMV-pCP) utilized in these experiments contained the BPM-V-pCP coding sequence, an intron-containing GUS gene, and the hygr omycin phosphotransferase gene. Southern blot hybridization analysis showed that 19 transgenic soybean plants selected for resistance to hygromycin co ntained the genes for GUS and BPMV-pCP. The progeny of five of these transg enic soybean plants (plants 137, 139, 157, 183, and 186) were characterized in detail. An additional transgenic plant (plant 200) contained the intron GUS and hygromycin resistance genes, but lacked the BPMV-pCP gene and was u sed as a negative control. Southern blot hybridization analysis of the five transgenic plants showed the presence of three copies of the T-DNA in a si milar banding pattern suggesting that they were derived from a single trans formation event. Western and northern blot analyses showed that the express ion levels of BPMV-pCP and pCP transcript were high in these five pCP plant s. Infectivity assays with detached leaves demonstrated that all five pCP p lants exhibited resistance to virus infection because they accumulated lowe r levels of BPMV compared with plant 200 and nontransformed controls. Unlik e the T-2 progeny of line 183-1 that segregated with respect to the pCP gen e and, consequently, to BPMV resistance, the T-2 progeny of the homozygous line 183-2 showed little or no symptoms in response to rub-inoculation with virions of a severe strain of BPMV. Although BPMV accumulation was evident in leaves on which viruliferous beetles were allowed a 72-h inoculation ac cess period, the upper noninoculated leaves of the T-2 progeny of line 183- 2 plants were symptomless and accumulated little or no virus. Because the p rogeny of this homozygous transgenic line exhibited systemic resistance, th ey could potentially be useful in generating commercial cultivars resistant to BPMV.