Abstract
Nine isolates of Aphelenchoides besseyi from two different hosts were studied. The isolates were identified at the species level according to morphometrics and fine structures observed under a scanning electron microscope. Two fern-originated isolates, Fu, and Fm, one rice-originated isolate, Rl, were not able to reproduce from a single juvenile, based on at least 50 replicates. The other six isolates were able to develop into a small population when inoculated with a single juvenile, demonstrating parthenogenesis. Crosses between isolates were conducted. In a compatibility cross experiment, three fern-originated isolates were selfed and crossed reciprocally, and all nine crossings had viable offspring. When fern isolates were used as paternal lines, the only two successful crosses were with the Rd line, and as maternal lines, only the Ff x Re and Fu x Rn crosses had viable offspring. Rl was used as the maternal line and Fm as the paternal line to study the inheritance of the bird’s-nest fern parasitism. Twenty of the 80 attempted crosses resulted in viable offspring and among these; six lines had the ability to parasitize on the bird’s-nest fern. When the F1 lines were back-crossed to the Rl maternal line, 20 viable offspring lines were obtained and among them 4 were able to parasitize bird’s-nest fern. These results indicate that bird’s-nest fern parasitism can be transferred to new generations by cross fertilization.
Highlights
Within the plant-parasitic Aphelenchoides genus, four species are well recognized: A. besseyi Christie, 1942; A. fragariae Christie 1932; A. ritzemabosi Steiner and Buhrer, 1932; and A. arachidis Bos, 1977
In the Aphelenchoides genus, A. ritzemabosi, A. fragariae, A. blastophthorus and A. composticola have been documented to reproduce by cross fertilization [5,6,7,8,9]
Noegel and Perry found that Aphelenchoides besseyi isolated from Chrysanthemum could not infect strawberry [17]; Rigges (1991) reported that A. besseyi isolated from strawberry could not infect rice, and vice versa [18]. These results show that A. besseyi, like Ditylenchus dipsaci, has different host preferences between isolates [19], but the existence of races of A. besseyi was not mentioned as a problem because the races were not differed by economically important hosts [17]
Summary
Within the plant-parasitic Aphelenchoides genus, four species are well recognized: A. besseyi Christie, 1942; A. fragariae Christie 1932; A. ritzemabosi Steiner and Buhrer, 1932; and A. arachidis Bos, 1977. The most common and economically important Aphelenchoides species in Taiwan is A. besseyi [1,2,3]. A. besseyi has been reported to parasitize rice (Oryza sativa L.), strawberry (Fragaria grandiflora Ehrn.), bird’s-nest fern (Asplenium nidus L.), and many other ornamental plants [2,3,4]. Sudakova and Stoyokov (1967) reported that reproduction occurred by parthenogenesis [11], while Franklin and Siddiqi (1972) [12] documented A. besseyi reproduction as amphimictic. In Taiwan, A. besseyi was originally reported as an amphimictic species [2,14]. Tzen (2003) recently reported the occurrence of both parthenogenesis and amphimixis among four isolates of A. besseyi [15]
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