Both wheat stripe rust and powdery mildew are important diseases in the world, which mainly infect the leaves and cause serious yield loss. In this study, the leaf samples of two varieties were collected from different pathogenic processes of stripe rust and powdery mildew that co-occurred in plants, and the internal transcribed spacer (ITS1) amplicon sequencing was introduced to analyse the structure and diversity of phyllosphere fungal communities. The results showed that the alpha diversity indices of the fungal communities were decreased with the pathogenic process, and the beta diversity among the different pathogenic process were significantly different as well. In addition, an Adonis analysis showed the pathogenic processes affected the structure of the fungal community, which could explain 45.6% of the variance in the community structure, on the contrary, the variety has no effect both on the community diversity and the structure. With the development of the pathogenic process, the abundance of both pathogens (Puccinia striiformis and Blumeria graminis) increased significantly, as well as for the relative abundance of some fungi (i.e., Alternaria spp., Cladosporium spp., etc.). The relative abundance of other genera (e.g., Aureobasidium, Epicoccum, etc.) increased at the early pathogenic stage, then decreased at the late pathogenic stage. Comprehensively, these fungi may have the potential to compete with pathogens for nutrients, which may be the target for the development of biological control agents.
There is growing concern about the impact of agricultural practices on water quality. The loss of nutrients such as nitrogen and phosphorous through agricultural runoff poses a potential risk of water quality degradation. However, it is unclear how dissolved organic matter (DOM) composition is associated with pollution levels in water bodies. To address this, we conducted a cross-year investigation to reveal the nature of DOM and its relationship to water quality in agricultural effluents (AEs) and livestock effluents (LEs). We discovered that DOM fluorescence components of AEs were mainly from autochthonous and terrestrial sources, while in LEs it was primarily from autochthonous sources. LEs showed a higher β:α and biological index (BIX) than AEs, indicating that LEs had higher biological activity. Compared to the LEs, DOM in AEs exhibited a higher humification index (HIX), illustrating that DOM was more humic and aromatic. Overall, our results suggest that the BIX and fluorescence index (FI) were best suited for the characterization of water bodies impacted by LEs and AEs. Excitation–emission matrix spectroscopy and parallel factor (EEMs-PARAFAC) analysis showed that DOM in AEs was mainly a humic-like material (~64%) and in LEs was mainly protein-like (~68%). Tryptophan-like compounds (C1) were made more abundant in AEs because of the breakdown of aquatic vegetation. The microbial activity enhanced protein-like substances (C1 and C2) in LEs. Our study revealed a positive correlation between five-day biochemical oxygen demand (BOD5) concentrations and tyrosine-like substance components, suggesting that fluorescence peak B may be a good predictor of water quality affected by anthropogenic activities. For both LEs and AEs, our results suggest that peak D may be a reliable water quality surrogate for total phosphorus (TP).
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