How does the host-specialized aphid deal with food deficiency？

Aphis gossypii Glover shows obvious host specialization, with cucurbit- and cotton-specialized biotypes or host races in many regions. Because its annual natal hostcrops senesce earlier the cucurbit-specialized biotype may suffer food deficiency. The method this biotype uses to overcome this challenge is still poorly understood. In orderto understand the potential of the cucurbit-specialized biotype aphids in host shift and usage, the performance of this biotype on cotton （Gossypium hirsutum）, a common butpoor quality host plant, was explored in this study. The cucurbit-specialized aphids could establish populations on cotton only when these plants had at least nine leaves, and subsequent populations developed rather slowly. The presence of whitefly populations on cotton improved the success rate of cucurbit-specialized aphids. The cucurbit-specialized aphidswere mainly distributed on the older leaves of cotton, with only a few settling on the upper leaves. The cucurbit-specialized aphids reared on cotton for 40, 54 and 61 days stillmaintained strong preference for their natal host plant, cucumber （Cucumis sativus）, rather than cotton, and their net reproductive rates and intrinsic rates of natural increase weredramatically lower when they were transferred onto new six-leaf cotton plants or detached leaves. Therefore, we concluded that the cucurbit-specialized aphids have the potentialto utilize mature or whitefly-stressed cotton plants, but that this feeding experience on cotton did not alter their specialization for cucurbits. Some cotton plants could act as atemporary host for the cucurbit-specialized aphids to overcome food deficiency arising from senescing cucurbits.

Rhizosphere fungal community assembly varied across functional guilds in a temperate forest

Background Rhizosphere fungi play an important role in plant community dynamics and biogeochemical cycling.While the drivers of fungal community assembly have been studied in varied ecosystems,it is still unclear how these processes function for rhizosphere soil fungi in temperate forests.Furthermore,it is unknown whether the relative contributions of important determinants remain consistent or vary across fungal ecological guilds.This study used high-throughput next-generation sequencing to characterize the fungal communities of 247 rhizosphere soil samples from 19 tree species in a temperate forest within Northeast China.We aimed to investigate how three important determinants in temperate forests(host tree species,neighbouring plant communities,and edaphic properties)influence the community assembly of fungal functional guilds in the rhizosphere soil of trees.Results We found that host tree species contributed more to plant pathogens’community composition than ectomycorrhizal fungi,and plant pathogens consistently showed higher host specialization than ectomycorrhizal fungi.Saprotrophs also showed high host specialization,which was mediated by the tree species’effect on rhizosphere soil pH.Although neighboring plant communities contributed remarkably to richness of all fungal guilds,this effect on fungal composition varied across functional guilds,with stronger effect for biotrophic guilds(plant pathogens and ectomycorrhizal fungi)than for non-biotrophic guild(saprotrophs).Neighboring plant communities shaped the ectomycorrhizal community composition strongly in all samples regardless of host trees’mycorrhizal type,whereas edaphic properties were the most important drivers for this guild in samples from only ectomycorrhizal-associated trees.Edaphic properties played an important role in shaping ectomycorrhizal and saprotrophic fungal compositions,indicating the importance of edaphic properties on the fungal functional guilds associated with the absorption and decomposition of nutrients.Conclusions These results demonstrated that rhizosphere soil fungal community assembly determinants varied across fungal guilds,reflecting their different ecological functions in temperate forest ecosystems.