In the quest for sustainable agriculture, arbuscular mycorrhizal fungi (AMF) have emerged as promising bioinoculants, fostering beneficial relationships with plant roots to enhance nutrient uptake and growth. However, the longevity of these introduced fungi and their impact on native fungal communities have remained largely unexplored. A recent study, led by Huiting Zhang from the Department of Horticulture at Washington State University, sheds light on these critical aspects, with implications for the commercial horticulture sector.
The study, published in the journal “Applied and Environmental Microbiology” (translated as “Applied and Environmental Microbiology”), focused on apple rootstocks, a cornerstone of orchard productivity. Zhang and her team investigated the stability of nursery-established AMF associations in various apple rootstock genotypes after transplantation into soil containing a known community of AMF. “We wanted to understand how commercial AMF inoculants interact with pre-existing fungal communities in the roots and how rootstock genotype might influence these interactions,” Zhang explained.
The researchers conducted a greenhouse experiment using four apple rootstock genotypes: G.890, G.935, M.26, and M.7. These rootstocks were inoculated with a commercially available, multi-species AMF consortium. The team then sequenced the nursery-derived AMF communities and assessed changes in AMF community structure following cultivation in pasteurized soil, both inoculated and non-inoculated.
The results revealed that the colonization potential of the inoculant was limited, suggesting that apple rootstocks serve as a significant source of inoculum from the nursery where they are produced. Interestingly, the rootstocks established relationships with introduced AMF in a genotype-specific manner. “This indicates that the genetic background of the rootstock plays a crucial role in determining the success of AMF colonization,” Zhang noted.
Moreover, the study found that the inoculant caused alterations to the resident AMF communities of both Geneva and Malling rootstocks, particularly affecting low-abundance taxa. This finding underscores the importance of considering the impact of introduced AMF on native fungal communities in agricultural practices.
One of the most intriguing discoveries was the identification of a unique, well-supported clade of unknown taxonomy through phylogeny-based analysis. This highlights the need for more accurate characterization of AMF communities and the potential limitations of relying solely on web-based databases for determining AMF identity.
The implications of this research are significant for the horticulture industry. Understanding the interactions between commercial AMF inoculants and pre-established AMF communities can lead to more effective and sustainable agricultural practices. “Our study demonstrates the potential for nursery-established AMF associations to be maintained when transplanted into the field,” Zhang said. “This knowledge can help industry practitioners improve product composition and consistency, ultimately enhancing plant productivity and sustainability.”
As the agricultural sector continues to seek innovative solutions for sustainable crop production, the insights gained from this study pave the way for more informed and strategic use of AMF inoculants. By leveraging the unique relationships between rootstock genotypes and AMF communities, farmers and horticulturists can optimize plant health and productivity, contributing to a more resilient and sustainable agricultural future.