| Summary: | 碩士 === 國立中興大學 === 植物病理學系所 === 94 === The root knot nematode caused galling, and the root lesion nematode caused dry rot and decay symptoms on yam tubers. The damage on tubers by these nematodes would increase with time and to deepen from surface to the inner tissue. Root knot nematode that caused galling was identified as Meloidogyne incognita by perineal pattern and body dimension. Root lesion nematode that caused dry rot was identified as Pratylenchus coffeae by morphomatrics and body dimension. Re-inoculation of Meloidogyne incognita and Pratylenchus coffeae onto yam tuber could result the same symptom 60 days after inoculation, and the same nematodes could be isolated again from yam tubers . At the beginning, Meloidogyne incognita and Pratylenchus coffeae penetrated into roots, to feed, and reproduce, and the developed tubers were infected by the offspring. The life cycle of Meloidogyne incognita in yam roots was 25 days, and Pratylenchus coffeae 24 days. The susceptibility test of 18 yam cultivars to Meloidogyne incognita and Pratylenchus coffeae indicated that the primate species from Zuojhen Tainan County was the most susceptible cultivar to both Meloidogyne incognita and Pratylenchus coffeae. In April, yams planted in fields that had Meloidogyne incognita and Pratylenchus coffeae, the maximum population of Meloidogyne incognita in soil was in September and Pratylenchus coffeae in October. Five nematicides and methyl bromide fumigant treatments could not kill all the nematodes inside the yam tubers. However, hot water treatments in 30 minutes over 51℃ or in 90 minutes over 50℃ could kill all Meloidogyne incognita within yam tubers, and 30 minutes over 49℃ or in 90 minutes over 48℃ could kill all Pratylenchus coffeae within yam tubers.
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