| Summary: | 碩士 === 國立中興大學 === 園藝學系所 === 98 === Lima beans (Phaseolus limensis Macf.) are self-pollinating crops, and there is at present no professional seed and nursery production system for certificated disease-free seeds. Bean farmers often keep their own planting stocks, and therefore viruses may be transmitted from seeds to plants. In this study, suspected infected leaf samples of lima beans were collected from Taichung and Tainan from June 2008 to November 2009, and indirect ELISA was performed with 10 antibodies for the detection and differentiation of different bean viruses. In the 76 specimens tested, 45 exhibited a positive reaction to potyvirus antibodies, including 40 to BCMV, 3 to BCMNV, 42 to BlCMV, 25 to BYMV, 11 to PSbMV, 36 to PStV and 3 to CMV. In addition, in 28 specimens suspicious symptoms were observed, but viruses were not detected by the antibodies. Further analysis revealed that viral infection of the lima beans was caused in the main by the bean common mosaic virus (BCMV) and the cucumber mosaic virus (CMV). Virus isolates (c8, c9 and c12) were obtained through single lesion isolation from BCMV-positive specimens, and the isolates were subjected to RT-PCR with a Pot I-HRP5 primer pair and then sequenced. The results demonstrated that isolate c9 had a maximum identify of 89.2% with the sequence of Accession U34972.1 (PStV). CMV isolates (CMV-lima) were also prepared and analyzed by RT-PCR using Cucumovirus-specific primers CPTALL-3 and CPTALL-5. The sequencing results indicated a identify of up to 95–96% between the CMV-lima isolates and subgroup IB (strains Nt9 and Tfn). The virus identification results confirmed that the BCMV identified in the beans was a strain of the peanut stripe virus (PStV), and the CMV was of the subgroup IB. Seed samples from the planting stocks of 8 bean farmers and 7 commercial seed nurseries were obtained from the Syuejia Township area in 2008 and were analyzed by indirect ELISA with BCMV and CMV antibodies. The analysis showed the virus-carrying rates of the 80 seeds from famers’ stocks to be 12.5% and 41.3% for BCMV and CMV, respectively, while the rates of the 105 seeds from seed nurseries were 3.8% and 4.8% for BCMV and CMV, respectively. Among 540 seedlings grown from seeds collected from four seed nurseries, one was infected with BCMV and one with CMV. When the seeds from single or multiple BCMV- or CMV-inoculated plants were analyzed, virus was detected in some of the seeds, while no disease symptoms were observed subsequently in their seedlings and plants. In BCMV- and CMV-infected plants, the virus was normally harbored in the seeds but only distributed in the seed coats. As seed coats were normally detached during germination, the virus did not stay with the seeds, and therefore the rate of transmission of BCMV or CMV to seedlings was far lower than the seed-born virus prevalence. Varied significant effects were observed in lima beans infected with different CMV strains, including reduction in plant height, lateral branch numbers, yield and pod malformation rates. Of the different CMV strains, CMV-Safflower was observed to have the worst effect. Comparing the use of virus-free lima seeds or the seeds from farms, the single pod weight and seed weight were significantly higher in the winter than the spring, the infection rate in winter was lower than that in the spring; and the yield was higher with the farmers’seeds than with the virus-free seeds.
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