SEED TRANSMISSION OF TURNIP MOSAIC VIRUS STRAIN I2 IN BRASSICA PLANTS
Viruses are widespread in nature and many of them cause plant diseases. Turnip mosaic virus (TuMV) is a member of genus Potyvirus in family Potyviridae and is the only potyvirus known to infect brassicas. When virus transmitted through seeds, the disease symptoms develop more slowly comparing to a vector-related infection. However, transmission of viruses through seeds of crop plants can cause very important economic consequences. Virus-infected seeds usually do not differ in appearance from healthy ones and the pathogen can be easily transported from one country to another, and provide sources of primary infection in field. Seeds of plants from several Brassica species were collected from TuMV-susceptible and tolerant infected Brassica plants to determine the fact of virus transmission through the seeds. TuMV presence in the seeds and obtained plantlets was identified by ELISA, RT-PCR and indicator plants reaction (by the Holmes' method). All diagnostic methods showed rate of TuMV infection in seeds from 0 to 40% depending on plant variety. Individual embryos contained virus infection as well that shows the possibility of transmission through inner seed contamination. For the first time, we found plant-genotype depended transmission of TuMV strain I2 with the seeds of brassicas. Sequencing of viral cDNA fragments of genes P1, NIb and CP for the virus detected in the seeds showed the nucleotide sequence identical to original strain I2. Search of the DNA sequences against the GeneBank showed their 99% identity to TuMV isolate UK1.