Trade-off between dispersal and reproduction in Aphelenchoides besseyi (Nematoda: Aphelenchoididae) harbored in Oryza sativa seeds in paddy fields

Abstract

The white tip nematode, Aphelenchoides besseyi, is a seed-borne ectoparasite of rice, Oryza sativa. Population parameters were compared with relation to seed specific gravity between infested and non-infested paddy fields to evaluate the effect of a nematode infestation on dispersal and survival of both host plant and nematode. When seeds from infested and non-infested paddy fields were floated on water, the proportion of light seeds (identified by floating at the water surface) was greater for infested field than for non-infested field. Light seeds showed smaller mean swelling, developed a smaller proportion of seminal roots, and required longer to produce the roots than did the heavy seeds from infested and non-infested fields. Nematode mortality was greater in light seeds than in heavy seeds. These results suggested that there was a trade-off between both the dispersal and competition of rice seeds and between dispersal and reproduction of nematodes harbored in the seed. Intriguingly, light seeds from infested fields showed a larger mean degree of swelling than did those from non-infested fields and light seeds harboring many nematodes had a well-developed endosperm, suggesting a host manipulation by the nematode.