Inoculation with Ericoid Mycorrhizal Associations Alleviates Drought Stress in Lowland and Upland Velvetleaf Blueberry (Vaccinium myrtilloides) Seedlings

Although velvetleaf blueberry (Vaccinium myrtilloides) is usually associated with sandy (upland) areas of the North American boreal forest, lowland populations can be also found in bogs, suggesting possible adaptations to different site conditions. In this study, we examined the role of ericoid mycorrhizal (ERM) fungi in conferring drought resistance to the upland and lowland velvetleaf blueberry seedlings. The seedlings were inoculated with four ERM fungi (Pezicula ericae, Pezoloma ericae, Meliniomyces variabilis, and Oidiodendron maius) isolated from the roots of ericaceous plants and grown under controlled environmental conditions in sterilized soil. The inoculated and non-inoculated (inoculation control) plants were subsequently subjected to three cycles of drought stress by withdrawing watering. Lowland plants appeared to benefit relatively more from mycorrhizal colonization, compared with the upland plants, in terms of plant growth and drought survival. After three weeks of treatments, the dry weights of non-inoculated well-watered upland plants were higher compared to the non-inoculated lowland plants. However, these differences were offset by the inoculation of plants with ERM fungi, some of which also significantly improved drought resistance characteristics of the upland and lowland plants. There were no major differences in the effects of different ERM fungal species on drought responses of upland and lowland plants. Of the examined ericoid mycorrhizal fungi, inoculation with Pezicula ericae was the most effective in conferring drought resistance characteristics to both upland and lowland seedlings and helped maintain higher shoot water potentials, net photosynthetic, and transpiration rates in plants subjected to drought stress.

Selection and Evaluation of Reference Genes for ddPCR-Based Transcript Abundance Studies in Oidiodendron Maius Across Varying Carbon Sources

Background When identifying transcript abundance in response to treatment, accurate quantification is critical, especially when examining subtle differences in expression. In particular, data normalization is necessary to account for differences among samples including those associated with RNA quantity and quality. Due to the capacity of droplet digital PCR to absolutely quantify the copy number of the target gene in a given sample, normalization, such as the use of an internal control gene, has not customarily been considered obligatory. Decades of quantitative PCR research have shown, however, that the use of endogenous controls undoubtedly aid in correcting sample variability. With our limited knowledge of gene function in many fungi, typical ‘housekeeping genes’ commonly used as internal references may not be relevant in these organisms. This study aimed to identify and validate suitable reference genes for transcript abundance studies in Oidiodendron maius, a globally distributed, model ericoid mycorrhizal fungus. Results A shortlist of 251 non-differentially expressed genes was generated from RNA-Seq analyses of O. maius grown on three different carbon sources or in symbiosis with Vaccinium myrtillus. Subsequently, a set of criteria (stable expression, valid annotation and relatively high expression) was applied to select three candidate reference genes. These three genes were validated across a further eleven carbon sources using ddPCR and the application of geNorm and NormFinder stability analysis algorithms. Expression stability analysis of three genes - EfTu, vma, and sar - confirmed their reliability as internal references; the geometric mean of their expression values demonstrated the highest stability as a normalization factor.Conclusions We propose the use of the geometric mean of O. maius genes EfTu, vma and sar as a reference tool to normalize RNA expression in ddPCR assays. These newly selected and validated reference genes will increase reliability and reproducibility when studying transcriptional responses of O. maius at different developmental stages and/or under a range of physiological conditions. In addition, the list of 251 non-differentially expressed genes can serve as a valuable resource for selecting reference genes for related experiments and enhances the limited information available on O. maius.

Attempts to eliminate Oidiodendron minus Barron from the substrate of Agaricus cultures

Among fungi which destroy <i>Agaricus</i> mycelium <i>Oidiodendron maius</i> Barron turned out to be most dangerous. Several simple experiments aimed at limiting its expansion were performed.