Traceability of Tobacco C151 Resistance to Potato Virus Y

C151 is a PVY-resistant flue-cured tobacco line, but the resistance mechanism is not clear. According to previous research results, the Va gene (Ntab0942120) in tobacco determines tobacco susceptibility to PVY, and Va deletion in the tobacco line VAM results in PVY resistance. To explore the correlation between the resistance mechanism of C151 and the Va gene, genomic-level detection of the Va gene was performed, and the results showed that there was no Va gene in C151. Pathological test results showed obvious susceptible symptoms in the C151 transformants with Va overexpression, which indicated that the resistance mechanism of C151 was caused by the loss of the Va gene. By examining molecular markers on chromosome 21, in which the Va gene is located, deletion of three markers adjacent to the Va gene occurred in C151, indicating that the PVY resistance of C151 also originates from a large deletion on chromosome 21; however, the mechanism behind this deletion remains unclear.