Determination of seed-born percentages of bean common mosaic necrosis virus (BCMNV) in three genotypes of Phaseolus vulgaris.

Bean common mosaic necrosis virus (BCMNV) is one of the most damaging viruses of bean that naturally transmitted by aphid in non persistent manner and through the seeds. BCMNV belongs to the genus Potyvirus and the family Potyviridae. During the growing season of 2004, bean leaf samples with viral symptoms were collected from Tehran province, Karaj region. DAS-ELISA by using BCMNV polyclonal antiserum (AS-0239, prepared in DSMZ, Germany) was conducted and samples with viral infection were distinguished. IC-RT-PCR was done to amplify the cp gene of isolates. The nucleotide sequence of one isolate was determined and analysis of this and other published sequences confirmed this isolate as BCMNV. The confirmed isolate was inoculated on three bean genotypes (butter bean ks-21478, kidney bean ks-31170, navy bean ks-41235) using 0.01 M Potassium phosphate buffer (pH = 7). After appearance of symptoms, the inoculated plants were tested by DAS-ELISA and IC-RT-PCR. In DAS-ELISA test, 68% infection of butter bean and kidney bean genotypes and only 7% infection of navy bean genotype were confirmed. In IC-RT-PCR by using specific primers (NL3), a 922 bp fragment was amplified in all genotypes, even symptomless plants and the ones which were negative in ELISA test. To determine the percentages of infected seed, harvested seeds were planted. Most of the seedlings in two-leaf stage died with black root symptoms. All seedlings were tested by DAS-ELISA and IC-RT-PCR. The results of these assays showed that the percentage of seed infected was 78%.