Sex ratio of Aphelenchoides besseyi within Oryza sativa seeds with relation to reproduction of rehydrated adult females
2022
Togashi, Katsumi | Hoshino, Shigeru
The white‐tip nematode, Aphelenchoides besseyi, is a seedborne ectoparasite of rice, Oryza sativa. It enters dehydrated quiescence within maturing seeds. Soaking dry seeds in water causes the quiescent nematodes to revive and the rehydrated nematodes emerge from the seeds. Two field nematode populations in Japan exhibited female‐biased sex ratios of living and dead adults in seeds (the proportion of females [female ratio] = 0.816, 0.803) and no influence of the number of adults in a seed on the female ratio. Single rehydrated female adults recovered from seeds reproduced without males whereas single juveniles did not do so. Most rehydrated female adults had sperms in the spermatheca. If all females mate with males in a seed before dehydration, the expected number of mated females, E(n), is given by the product of the female ratio, the number of adults in a seed (n) and the probability that both sexes occur in a seed. The E(n) value peaked at an n‐specific female ratio (fₒₚₜ). When the female ratio was invariable (ffᵢₓ), the expected number of mated females per seed, ∑n=2∞Eng(n), peaked at an ffᵢₓ value (optimum ffᵢₓ value) of 0.794 and 0.788 for the two populations, where g(n) expressed the proportion of seeds harbouring n adults (n ≥ 2). The overall fit of actual numbers of recovered females to the expectations obtained from the optimum ffᵢₓ value was better than that to the expectations from the n‐specific fₒₚₜ values. The optimum ffᵢₓ values were close to the actual female ratios.
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