Diversity and Phenology of Soybean Seed Fungal Endophyte Communities in the Upper Midwest United States

Abstract

Infection over time by endophytic fungi in soybean seed and pods was documented in Iowa and Wisconsin in 2018. Three reproductive stages were sampled from six cultivars, with maturity groups (MG) ranging from 1.1 to 4.7, and included 216 blemish-free pods and 1,836 healthy seeds that were heavily disinfested to remove epiphytes. Thirty-five species and 11 genera were identified from 1,799 isolates using morphological and molecular evidence. Alternaria, Diaporthe, and Fusarium were dominant. The timing of endophyte infection was documented relative to MG. The lowest number of fungi were recovered from seed at R6, and infection sharply increased at R7. The abundance of Diaporthe and Fusarium isolates differed across MG and reproductive stage; shorter MGs had more Diaporthe isolates at earlier reproductive stages than longer MGs. Fusarium counts differed across MG but did not show consistent trends with seed maturity. Alternaria counts declined as seed matured but were not affected by MG. We used nonmetric multidimensional scaling to elucidate the phenology of seed infection within the endophyte community. This method helps represent the data in a lower dimension by measuring the similarity or dissimilarity between data points, making it a useful tool for grouping similar endophyte communities. The nonmetric multidimensional scaling ordination analysis of fungal taxa within endophyte communities revealed that the dominant genera in filled green pods were highly similar. However, this similarity was not observed among different stages of seed development, indicating that each taxon had distinct modes of infecting the seeds. [Figure: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Keywords

• Alternaria
• Diaporthe
• Fusarium
• Glycine max
• logistic regression
• microbial communities