| The brown planthopper(BPH), Nilaparvata lugens is one of the most important rice pests in China.Arsenophonus is one of symbionts of many insects and was first observed in Nasonia vitripennis.Arsenophonus produces strongly female-biased brood by killing nearly80%sons, thus called son-killersymbiont. Many studies found that it was not only killing sons, but also associated with the immunity,nutrition requirement and host adaptation of insect hosts. Recently studies focused on the function of theArsenophonus. Studies showed BPH body also containing the Arsenophonus and its infection rate variesamong different virulent BPH populations. But how does Arsenophonus interact with BPH still largelyunknown. For example, the transfer mode of Arsenophonus and other biological function is still notknown. Therefore, this article studied on the transfer mode of Arsenophonus, and its effect on thereproduction, virulence and resistance to the Metarhizium anisopliae of positive (includingArsenophonus) and negative (excluding Arsenophonus) BPH. The results are as follows:1. The transfer mode: According to the reciprocal cross tests, we found that the rate of offspringcontaining Arsenophonus was as same as the rate of their mothers. The result revealed that theArsenophonus was maternally inherited in BPH.2. The effect of Arsenophonus on the reproduction of BPH: The positive and negative newlyemerged BPH were paired and reared respectively. The numbers and sex rates of offspring wererecorded. The results indicated Arsenophonus did not significantly impact reproductive rate and sexratio of BPH. It is suggested that Arsenophonus had no male-killing function to BPH.3. Virulence:1) By observing and comparing two consecutive generations of Arsenophonusnegative and positive BPH populations on resistant rice varieties Mudgo. We found that the eclosionrate, nymphal development duration, newly emerged adult fresh weight were different between negativeand positive populations, and some indicators showed significant difference, but these parameters variedamong different generations. The fecundity of Arsenophonus positive population were lower than that ofnegative population. The trend became significantly as long as the replication increased. The range ofaveraged fecundity was60~189eggs per female. So we concluded that Arsenophonus can influence theBPH virulence on Mudgo.2) With the mixture of1:1positive and negative BPH reared on Mugdo andTN1over21generations consecutively, the positive rate of BPH on TN1were all higher than that onMugdo for each generation. Of four repeats on the Mudgo, the positive rate of BPH dropped to0%reared on repeat one and on repeat2since the ninth generation. The positive rate of BPH on another tworepeats remained on a relatively high level toward the21stgeneration. The result indicated that theinfection of Arsenophonus may be differentiated among different species or strains and Arsenophonuscan influence the BPH virulence on Mugdo. Repeated the experiments found that the infect rate werenot decreased after seven generations rearing on Mudgo. There were two different sequences found withcloning and comparing16S-23S rDNA of Arsenophonus in the BPH populations, but the relationship ofArsenophonus strains with virulence needs further study. 4.4. The resistance of BPH with Arsenophonus to Metarhizium anisopliae: Through compared themortality of positive and negative BPH population by inoculating the fungal pathogen to newly emergedfemale brown planthopper, the results showed that the infection rate of negative population to M.anisopliae ARSEF1764(55.2%0.9%)was significantly higher than that of positive population (32.5%4.7%), which indicated Arsenophonus could improve the resistance of BPH to M. anisopliaeARSEF1764. |
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