Wheat phyllosphere yeasts degrade propiconazole

Applied microbiology of the phyllosphere

The phyllosphere, or plant leaf surface, represents a microbial ecosystem of considerable size, holding extraordinary biodiversity and enormous potential for the discovery of new products, tools, and applications in biotechnology, agriculture, medicine, and elsewhere. This mini-review highlights the applied microbiology of the phyllosphere as an original field of study concerning itself with the genes, gene products, natural compounds, and traits that underlie phyllosphere-specific adaptations and services that have commercial and economic value for current or future innovation. Examples include plant-growth-promoting and disease-suppressive phyllobacteria, probiotics and fermented foods that support human health, as well as microbials that remedy foliar contamination with airborne pollutants, residual pesticides, or plastics. Phyllosphere microbes promote plant biomass conversion into compost, renewable energy, animal feed, or fiber. They produce foodstuffs such as thickening agents and sugar substitutes, industrial-grade biosurfactants, novel antibiotics and cancer drugs, as well as enzymes used as food additives or freezing agents. Furthermore, new developments in DNA sequence-based profiling of leaf-associated microbial communities allow for surveillance approaches in the context of food safety and security, for example, to detect enteric human pathogens on leafy greens, predict plant disease outbreaks, and intercept plant pathogens and pests on internationally traded goods. KEY POINTS: • Applied phyllosphere microbiology concerns leaf-specific adaptations for economic value • Phyllobioprospecting searches the phyllosphere microbiome for product development • Phyllobiomonitoring tracks phyllosphere microbial profiles for early risk detection.

Biological Control of Aspergillus flavus by the Yeast Aureobasidium pullulans In Vitro and on Tomato Fruit

Aspergillus flavus is an important pathogenic fungus affecting many crops and is one of the main sources of their aflatoxin contamination. The primary method of limiting this pathogen is using chemical fungicides, but researchers focus on searching for other effective agents for its control due to many disadvantages and limitations of these agrochemicals. The results obtained in the present study indicate the high potential of two yeast strains, Aureobasidium pullulans PP4 and A. pullulans ZD1, in the biological control of A. flavus. Under in vitro conditions, mycelial growth was reduced by 53.61% and 63.05%, and spore germination was inhibited by 68.97% and 79.66% by ZD1 and PP4 strains, respectively. Both strains produced the lytic enzymes chitinase and β-1,3-glucanase after 5 days of cultivation with cell wall preparations (CWP) of A. flavus in the medium as a carbon source. In addition, the tested yeasts showed the ability to grow over a wide range of temperatures (4-30 °C), pH (4-11), and salinity (0-12%) and showed tolerance to fungicides at concentrations corresponding to field conditions. Both isolates tested were highly tolerant to cupric oxychloride, showing biomass gains of 85.84% (ZD1) and 87.25% (PP4). Biomass growth in the presence of fungicides azoxystrobin was 78.71% (ZD1) and 82.65% (PP4), while in the presence of difenoconazole, it was 70.09% (ZD1) and 75.25% (PP4). The yeast strains were also tested for antagonistic effects against A. flavus directly on tomato fruit. Both isolates acted effectively by reducing lesion diameter from 29.13 mm (control) to 8.04 mm (PP4) and 8.83 mm (ZD1).

Ecology and functional potential of phyllosphere yeasts

The phyllosphere (i.e., the aerial parts of plants) harbors a rich microbial life, including bacteria, fungi, viruses, and yeasts. Current knowledge of yeasts stems primarily from industrial and medical research on Saccharomyces cerevisiae and Candida albicans, both of which can be found on plant tissues. For most other yeasts found in the phyllosphere, little is known about their ecology and functions. Here, we explore the diversity, dynamics, interactions, and genomics of yeasts associated with plant leaves and how tools and approaches developed for model yeasts can be adopted to disentangle the ecology and natural functions of phyllosphere yeasts. A first genomic survey exemplifies that we have only scratched the surface of the largely unexplored functional potential of phyllosphere yeasts.