| Summary: | 碩士 === 國立中興大學 === 植物病理學系所 === 100 === In August 2011, the cactus nematode Cactodera cacti were first observed on roots of dragon fruit (Holycereus spp.) in central and southern Taiwan. The brown lemon-shaped cysts show circumfenestrate on the vulva cone top with eggs inside, the egg shell was punctuate when observed under SEM. The Second-stage juvenile is vermiform, four incisures were observed in the lateral field. A total of 6 gerographical populations were established from the survey, and the nematodes were inoculated and maintained on dragon fruits for the following experiments. Using the modified primer set to amplify the rDNA from the 7 populations, all resulted a 981 bp fragment. After sequencing, 28 clones from the 7 population resulted in 16 haplotypes. The neighbor-joining phylogeny tree showed the haplotypes 9 to 16 from the middle Taiwan were in the same branch with the Germany and Iran isolates (accession number:AF498393 ; HQ260422). These haplotypes were found from the first breeding location of dragon fruit in central Taiwan, indicating the ancestor of current populations of C. cacti might come from central Taiwan. The reported hosts of C. cacti containing 3 families: Cactaceae, Euphorbiaceae, and Umbelliferae. Seventeen plant species from 5 families were included this study for the host range test. Among them, Hylocereus triagularis, Mammillaria spinosiassima, Notocactus ottonis, Mammillaria sempervivi, Cereus peruvianus, Coryphantha elephantidens, Echinopsis eyriesii, Discocactus heptacanthus, Opuntia stricta var. dillenii of the familiy Cactaceae proved to be the host of C. cacti. Cactaceae Echinocactus grusonii, Rhipsalis cereuscula, Umbelliferae Apium graveolens, and the economically important plants Beta vulgaris, Solanum tuberosum, and Glycine max were not the host of C. cacti. In the hatching rate test, the cysts were put in water and incubate at 4, 16, 20, 24, 28, 32℃ for five days, respectively, the egg hatching rate under different temperature showed no significant difference between these treatments, however, J2 were more active under the 32℃ treatment. C. cacti was inoculated on dragon fruits, and incubated under 32℃ for the life cycle experiment. The nematode completed their life cycle at the 40th day in the first experiment and 35th in the second experiment. C. cacti caused no symptoms on the above-ground parts, and its damage to the dragon fruit yield should be investigated in the future.
|
|---|
