Investigation Of Virus Disease Of Faba Bean And Pea In Qinghai And Complete Sequence Analysis Of Bean Yellow Mosaic Virus(BYMV)

Qinghai Province is the major faba bean and pea producing region in China.Viral diseases is one of the major limiting factors for faba bean and production there. Though 3 viral diseases were found in 2005 and 2006, Bean yellow mosaic virus (BYMV) was the most serious based on the detection of faba bean and samples by Tissue Blot Immunoassay (TBIA).According to the sequences of the coat protein gene of BYMV, a pair of primers were designed and used to amplify BYMV coat protein(CP) gene in seven faba bean and one pea isolates, Seven from faba bean and 1 from pea by reverse transcription PCR (RT-PCR). The sizes of cloned fragment were 1071 nucleotides, containing CP of 822 nucleotides, deduced 273 amino acids. The homology of nucleotides and deduced amino acid sequences of eight isolates were 99.0% to 99.9% and 99.3% to 100.0%, respectively. The homology of CP and deduced amino acid sequences between eight isolates and eighteen isolates was 83.6% to 99.9% and 90.1 % to 100%, respectively. The homology of CP of the BYMV-Chinese isolates is close to the BYMV-Yunnan isolates. The NAG motif, a basic structure for aphid transmission motif of CP in BYMV, was present in all eight isolates.The genomic sequence of 9-16 was determined by sequencing 6 overlapping viral cDNA clones generated by RT-PCR, which first represented the complete sequence for the virus in China. The sequence is 9547 nucleotides in length excluding the 3′terminal poly (A) tail and contains a single open reading frame of 9168 nucleotides encoding a large polyprotein of 3056 amino acids with predicted Mr of 352.6kD. The genome of 9-16 has a 205 nt 5′-non coding and a 174 nt 3′-non coding region. The size of the genome and the encoded polyprotein are in agreement with other potyviruses and contain nine putative proteolytic cleavage sites and motifs conserved in homologous proteins of other potyviruses. The P1 and P3 were the most variable proteins while CI, NIb and CP were relatively conserved.The resistence of 51 faba bean and pea seedlings to BYMV was investigated by grinding inoculation. Results indicated that only H2508,G0861,G4774 and G4835 were resistant to BYMV, H2063,H2412,FE3 and 12 pea cultivars were moderately resistant, and others were susceptible or highly susceptible.