Tremellomycetes Yeasts in Kernel Ecological Niche: Early Indicators of Enhanced Competitiveness of Endophytic and Mycoparasitic Symbionts against Wheat Pathobiota.

Vladimir Vujanovic

doi:10.3390/plants10050905

Abstract

Tremellomycetes rDNA sequences previously detected in wheat kernels by MiSeq were not reliably assigned to a genus or clade. From comparisons of ribosomal internal transcribed spacer region (ITS) and subsequent phylogenetic analyses, the following three basidiomycetous yeasts were resolved and identified: Vishniacozyma victoriae, V. tephrensis, and an undescribed Vishniacozyma rDNA variant. The Vishniacozyma variant’s clade is evolutionarily close to, but phylogenetically distinct from, the V. carnescens clade. These three yeasts were discovered in wheat kernel samples from the Canadian prairies. Variations in relative Vishniacozyma species abundances coincided with altered wheat kernel weight, as well as host resistance to chemibiotrophic Tilletia (Common bunt—CB) and necrotrophic Fusarium (Fusarium head blight—FHB) pathogens. Wheat kernel weight was influenced by the coexistence of Vishniacozyma with endophytic plant growth-promoting and mycoparasitic biocontrol fungi that were acquired by plants. Kernels were coated with beneficial Penicillium endophyte and Sphaerodes mycoparasite, each of which had different influences on the wild yeast population. Its integral role in the kernel microbiome renders Vishniacozyma a measurable indicator of the microbiome–plant interaction. The ability of NGS technology to detect specific endophytic DNA variants and early changes in dynamics among symbionts within the kernel ecological niche enables the prediction of crop disease emergence, suggesting that advanced microbiological testing may be a potentially useful tool for both phytoprotection and more efficient wheat breeding programs.

Highlights

The seed, grain, or kernel is the reproductive unit of plants [1]
Since Tremellales mycoparasites tend toward plant–host specificity, the present study has focused on the identification of uncharacterized yeast populations in wheat kernels from previous field and current greenhouse samplings
This possibility coincides with our previous results, which indicate that a plant growth-promoting (PGP) inoculant shifts the microbial composition structure in wheat kernels by increasing Trichocomaceae (e.g., Penicillium spp.) and tremelloid-yeast populations [2], which is to the detriment of Exobasidiomycetes (e.g., Tilletia) populations

Summary

Introduction

The seed, grain, or kernel is the reproductive unit of plants [1]. In wild as well as domesticated Triticale plants, kernels simultaneously establish multiple symbiotic associations with endophytic and mycoparasitic fungi, which can, respectively, improve plant traits and increase resistance to pathogenic fungi. Given that the health of plants depends on the health of the kernels from which they develop, it is important to understand the role of mycovitality, which is the relationship between the grain and endophytic microbes [3,4,5,6] that acts as a key regulatory mechanism affecting host physiology and phenotypic characteristics. Understanding this relationship is a critical first step toward enhancing developmental events and early resilience to environmental stressors, including pathobiota, in the plant host and is a cornerstone of pre-germination care [7]

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Discussion

Conclusion