PS 31-125 - Kin relationships can alter the strength of plant-soil feedbacks

Background/Question/Methods

Intraspecific variation may play a key role in understanding the relationships between plants and their interactions with soil microbial communities. The soil microbial communities of individual plants may differentially impact their own seedlings, altering their success. These effects on individuals can generate variation in responsiveness between kin and non-kin seedlings. This study investigated 1) if the relatedness of a seedling to the conditioning plant affects plant-soil feedbacks and 2) if seedling interactions differ when growing in soil inoculated with microbes representing the maternal or paternal environments.

We explored these questions in established Solidago altissima clones grown in a common garden. Seedlings of known parentage were generated via hand pollinations as S. altissima is self-incompatible. Seedlings from these crosses were grown in media inoculated with soils from the maternal, paternal, or unrelated clones and compared to autoclaved control inocula. Sixty days after inoculation, above- and below-ground biomasses were harvested, dried, and weighed.

Results/Conclusions

We found that the soil inocula generated from S. altissima clones had an overall negative effect of seedling biomass. Furthermore, seedlings inoculated with maternal or paternal soils experienced a larger negative effect than seedlings inoculated with unrelated soils. Relatedness to the culturing plant strongly reduced seedling growth, whereas unrelated soils were slightly more variable but less negative. However, there was variation among crosses in their responsiveness to soil microbes, with some having little impact on plant growth. Maternal and paternal soil microbial communities typically affected seedling growth similarly, suggesting genetic influences rather than maternally inherited non-genetic effects. Relatedness of seedlings to the plants that cultured the soil microbial community greatly influenced the direction and magnitude of plant-microbe interactions. Our data argue that genetic relatedness may represent a largely unexplored source of heterogeneity in plant-soil feedbacks. To understand how soil microbes determine plant population dynamics, we will need to better incorporate intraspecific variation into research.