台灣地區Xiphinema hunaniense之鑑定與變異

Abstract

Eight geographical populations of Xiphinema hunaniense were isolated successively from the rhizosphere of litchi, sweet orange, pear, longan, buntan, and loquat using modified Baermann funnel method in central and south parts of Taiwan during 1998 to 2003. Based on the matchable length of replacement odontostyle and functional odontostyle, and also the evident gap of replacement odontostyle and total stylet length between the four successive juvenile stages and adult, it assured that examined specimens of each population were not mixed with other morphologically similar Xiphinema species. The female morphometric results indicated that only the Xhun8 showed differences in mean length of total stylet (functional odontostyle plus odontophore) and tail compared with the other populations, but the ranges of the above two items were overlapped obviously. As to the juveniles, only the fourth juvenile stage of Xhun8 showed differences to the other populations. The ITS-1 sequence size of rDNA fragments from Xhun2, 3, 6, 8 were ranged from 1128 to 1131 bp, its pairwise percentage dissimilarity were 0.18~2.40. Concluded from the above comparisons of morphometrics of females and juveniles, and the sequence data of rDNA, it indicated that the differences existed in Xhun8 should be ascribed to the intraspecific variation of X. hunaniense. The identification of X. hunaniense males was the first report in the world and its morphometrics and the shape of lip region and tail pegs were almost identical with that of the females, and the numbers of supplements were 7 to 8. Until now, only the southeast Mainland China and Taiwan have reported the X. hunaniense, but some of the morphometrics have showed variance to each other. However, to decide that whether these differences were intraspecific or interspecific variation, or to clarify the relationships with X. brasiliense or X. radicicola, both were morphologically close to X. hunaniense, collecting more morphometric data of the juveniles, males and the sequences of rDNA of different geographical populations of X. hunaniense, especially from the Mainland China, would be the only feasible method.