Wednesday, November 15, 2006 - 9:30 AM
246-5
Reaction of Current Soybean Cultivars in Arkansas to Soybean Mosaic Virus and Tobacco Ringspot Virus.
Soybean mosaic virus (SMV) and Tobacco ringspot virus (TRSV) are two important viral pathogens in soybean. Seven SMV strains (G1 to G7) have been reported in the U.S. and three resistance loci (Rsv1, Rsv3, and Rsv4) have been identified. There are various TRSV isolates observed, but no host resistance reported so far. The objective of this study was to screen modern soybean cultivars for resistance or tolerance to SMV or TRSV. A total of 303 cultivars currently grown in Arkansas were screened in the greenhouse for their reactions to SMV and TRSV. Each cultivar was inoculated with two SMV strains (G1 and G7) and two TRSV isolates (mild and severe). The results of G1 inoculation showed that 221 cultivars were susceptible(S), 31 resistant(R), 9 necrotic (N), and 42 mixed in reactions. The G7 screening revealed that 273 cultivars were S, 21 R, 5 N, and 4 mixed in reactions. The 28 cultivars resistant to G1 but susceptible or necrotic to G7 carry Rsv1 alleles for SMV resistance, whereas the 16 cultivars susceptible to G1 but resistant to G7 contain Rsv3 alleles. The 9 cultivars necrotic to G1 may carry Rsv1-n, while 2 cultivars resistant to both G1 and G7 may contain Rsv4 or two resistance genes. There was no resistance to TRSV, all cultivars showed bud blight 10 days after inoculation. However, 52 cultivars recovered 5 weeks after inoculation (more than 80% of the plants grew out of the bud blight and formed new leaves). The recovered plants, although systemically infected, clearly showed tolerance to TRSV at a later stage.
Recorded presentation