The decay and fungal succession of apples with bitter rot across a vegetation diversity gradient

Bitter rot is a disease of apple caused by fungi in the genus Colletotrichum. Management begins with removal of infected twigs and fruits from tree canopies to reduce overwintering inoculum. Infected apples are usually tossed to the orchard floor, which is generally managed as herbicide-treated weed-free tree rows, separated by grass drive rows. We monitored decay rates and succession of fungi of apples with bitter rot in tree canopies, and on the soil surface in tree rows, grass drive rows, and nearby diverse plant communities. We hypothesized that decay would occur most rapidly within diverse plant communities, which would provide a more diverse array of potential fungal decomposers. Apples in tree canopies became dry and mummified and had more Colletotrichum gene marker copies the following growing season than did apples on the soil surface. Of the soil surface samples, those in grass drive rows and diverse plant communities had higher moisture, faster decay rates, and sharper decreases in Colletotrichum gene marker copies than apples in tree rows. Fungal composition across all decaying apples was dominated by yeasts, with higher genus-level richness, diversity, and evenness in apples from tree canopies than those on the soil surface. In soil surface apples, we observed clear successional waves of Pichia, Kregervanrija, and [Candida] yeasts, with similar but distinctly diverging fungal composition. Our results show that orchard floor management can influence fungal succession in apples with bitter rot, but suggests that bitter rot management should primarily focus on removing infected apples from tree canopies.

An evolutionary signal to fungal succession during plant litter decay

ABSTRACT Ecologists have frequently observed a pattern of fungal succession during litter decomposition, wherein different fungal taxa dominate different stages of decay in individual ecosystems. However, it is unclear which biological features of fungi give rise to this pattern. We tested a longstanding hypothesis that fungal succession depends on the evolutionary history of species, such that different fungal phyla prefer different decay stages. To test this hypothesis, we performed a meta-analysis across studies in 22 different ecosystem types to synthesize fungal decomposer abundances at early, middle and late stages of plant litter decay. Fungal phyla varied in relative abundance throughout decay, with fungi in the Ascomycota reaching highest relative abundance during early stages of decay (P < 0.001) and fungi in the Zygomycota reaching highest relative abundance during late stages of decay (P < 0.001). The best multiple regression model to explain variation in abundance of these fungal phyla during decay included decay stage, as well as plant litter type and climate factors. Most variation in decay-stage preference of fungal taxa was observed at basal taxonomic levels (phylum and class) rather than finer taxonomic levels (e.g. genus). For many finer-scale taxonomic groups and functional groups of fungi, plant litter type and climate factors were better correlates with relative abundance than decay stage per se, suggesting that the patchiness of fungal community composition in space is related to both resource and climate niches of different fungal taxa. Our study indicates that decomposer fungal succession is partially rooted in fungal decomposers’ deep evolutionary history, traceable to the divergence among phyla.

Effect of Temperature Changes on the Bacterial and Fungal Succession Patterns during Composting of Some Organic Wastes in Greenhouse

Aim: Organic wastes were composted and the effect of temperature changes on the bacterial and fungal succession patterns studied. Study Design: The wastes which included cow dung (CD), pig waste (PW), poultry litter (PL) and source-separated municipal solid waste (MSW) and their combinations: PL+MSW, PW+MSW and CD+MSW were allowed to decompose for 70 days in a greenhouse. Place and Duration of Study: This study was carried out between September 2017 and January 2018, in the greenhouse of the Agricultural Research Farm of Federal University of Technology, Owerri, Nigeria. Methodology: The wastes were allowed to decompose for 70 days in a greenhouse using the modified windrow method of composting. Standard microbiological methods were used to monitor temperature changes in compost piles as well as changes in bacterial and fungal populations. Results: Results revealed that changes in temperature affected microbial composition in the compost piles. The highest temperature recorded was 60oC for cow dung (CD) compost pile while at maturity the temperature in all the compost piles ranged between 27°C to 30°C. Different bacterial and fungal populations were isolated during the thermophilic and mesophilc phases of composting. Bacteria isolates included species of Staphylococcus, Proteus, Klebsiella, Salmonella, Alcaligenes, Serratia, Lactobacillus and Pseudomonas. Others included Enterobacter, Bacillus, Streptococcus, Corynebacterium and Micrococcus spp. Fungal species isolated included Candida, Saccharomyces, Rhizopus, Aspergillus, Mucor and Fusarium. Conclusion: The presence of some plant growth promoting (PGP) bacteria at the end of composting qualifies organic waste composts as effective nutrient sources for crop production and can be considered as potential alternatives to chemical fertilizers.