Weather in two climatic regions shapes the diversity and drives the structure of fungal endophytic community of bilberry (Vaccinium myrtillus L.) fruit

BACKGROUND

Bilberry (Vaccinium myrtillus L.) is one of the most important economic and natural resources in Northern Europe. Despite its importance, the endophytic fungal community of the fruits has rarely been investigated. Biogeographic patterns and determinants of the fungal diversity in the bilberry fruit are poorly understood, albeit fungal endophytes can have a close relationship with the host plants. Here, we investigated the effect of climatic regions, and their weather conditions within growth season and soil properties on fungal endophytic communities of bilberry fruits collected from northern and southern regions of Finland using high-throughput sequencing technology targeting the internal transcribed spacer 2 ribosomal DNA region for fungi.

RESULTS

Species richness and beta diversity (variation in community structure) were higher in the southern compared to the studied northern region. The weather condition of the growth season drove both fungal richness and community structure. Furthermore, abundance of the genera Venturia, Cladosporium, and Podosphaera was influenced by the weather, being different between the south and north regions.

CONCLUSIONS

We conclude that diversity and assembly structure of the fungal endophytes in bilberry fruits follow similar patterns as for foliar fungal endophytes, being shaped by various environmental factors, such as the climate and surrounding vegetation.

Aquatic macrophyte growth season in Central and Northern European Union and the implications for aquatic macrophyte risk assessments for herbicides

Under current European Union regulation, the risks to aquatic organisms must be assessed for uses of plant protection products (PPPs) that may result in exposure to the environment. For herbicidal PPPs, aquatic macrophytes are often the most sensitive taxa. For some herbicidal modes of action, macrophytes may be affected only while they are actively growing. For the risk assessment, it is therefore useful to know whether application timings would result in surface water exposure during periods when aquatic macrophytes are actively growing (therefore potentially resulting in effects). Toxicity endpoints, which are based on studies with active growth, may be overconservative in cases where exposure of PPPs will not co-occur with active macrophyte growth. A comprehensive literature search was performed, using systematic and manual approaches, with the aim of identifying the main active growth period for macrophytes in natural freshwater bodies in climates relevant to the Central and Northern zones of the European Union. The results of the searches were screened initially to identify all potentially relevant references, for which a full evaluation was then performed. Reliability was assessed using the principles of the Klimisch scoring system. As part of the full evaluation, growth periods were identified for each macrophyte species studied. Finally, the extracted growth periods were considered together to determine an overall active growth period for aquatic macrophytes representative of the Central and Northern EU zones. Based on this literature review, the active growth period identified for most aquatic macrophyte species representative of the Central and Northern EU zones is April to September. Relating to the regulatory implication of these results, it may be possible to conclude a low risk for aquatic macrophytes if the predicted surface water exposure period for certain PPPs is demonstrated to be outside the periods of active growth. Integr Environ Assess Manag 2023;00:1-15. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Community structure and function of epiphytic bacteria attached to three submerged macrophytes

In aquatic ecosystems, large amounts of epiphytic bacteria living on the leaf surfaces of submerged macrophytes play important roles in affecting plant growth and biogeochemical cycling. The restoration of different submerged macrophytes has been considered an effective measure to improve eutrophic lakes. However, the community ecology of epiphytic bacteria is far from well understood for different submerged macrophytes. In this study, we used quantitative PCR, 16S rRNA gene high-throughput sequencing and functional prediction analysis to explore the structure and function of epiphytic bacteria in an aquatic ecosystem recovered by three submerged macrophytes (Hydrilla verticillata, Vallisneria natans and Potamogeton maackianus) during two growth periods. The results showed that the community compositions and functions of epiphytic bacterial communities on the submerged macrophyte hosts were different from those of the planktonic bacterial communities in the surrounding water. The alpha diversity of the epiphytic bacterial community was significantly higher in October than in July, and the community compositions and functions differed significantly in July and October. Among the three submerged macrophytes, the structures and functions of the epiphytic bacterial community exhibited obvious differences, and some specific taxa were enriched on the biofilms of the three plants. The alpha diversity and the abundance of functions related to nitrogen and phosphorus transformation were higher in the epiphytic bacteria of P. maackianus. In summary, these results provide clues for understanding the distribution and formation mechanisms of epiphytic bacteria on submerged macrophyte leaves and their roles in freshwater ecosystems.

Nitrate leaching from open-field and greenhouse vegetable systems in China: a meta-analysis

The potential for nitrate leaching in Chinese vegetable systems is substantial because of high inputs of nitrogen (N) fertilizer and water. To quantify the nitrate leaching and identify the key controlling factors in Chinese vegetable systems, we conducted a meta-analysis that included 221 data sets from 18 field studies. The results revealed that nitrate leaching over the entire crop growing season in Chinese vegetable systems was very high and averaged 79.1 kg N ha^-1 and primarily resulted from extremely high N fertilizer inputs (in average 423 kg N ha^-1). Nitrate leaching was, on the average, 63.9% greater in the greenhouse systems (98.0 kg N ha^-1) than in open-field systems (59.8 kg N ha^-1). The leaching factor, defined as the proportion of the quantity of N applied to soils that was lost due to nitrate leaching, averaged 14.6% overall and was significantly lower in greenhouse systems (10.9%) than in open-field systems (18.4%). This difference appears to be due to lower of the total water inputs (irrigation + precipitation) in greenhouse systems. Nitrate leaching increased with water input, the number of growing days, and the N rate. The nitrate leaching response to increasing N rate was linear. The leaching factor significantly increased with water input but was not affected by the N rate or the number of growing days. Compared with application of synthetic fertilizer alone, the application of manure alone or manure plus synthetic fertilizer significantly reduced both the nitrate leaching and the leaching factor in open-field and greenhouse systems. These results suggest that nitrate leaching in Chinese vegetable systems can be reduced by optimizing rates of N and water supply to synchronize crop needs. Application of mixed synthetic N fertilizer and manure is more effective in reducing nitrate leaching, compared to synthetic N only.

Phenology of plants in relation to ambient environment in a subalpine forest of Uttarakhand, western Himalaya

Observations on phenology of some representative trees, shrubs, under-shrubs and herbs in a subalpine forest of Uttarakhand, western Himalaya were recorded. With the commencement of favorable growth season in April, occurrence of leaf fall was indicatory growth phenomenon in Quercus semecarpifolia, Q. floribunda and Abies spectabilis. However, active vegetative growth in herbaceous species starts onward April and fruit maturation and seed dehiscence are completed from mid of September to October. In general, vegetative growth and reproductive stages in majority of the studied species seems to be dependent on adequate moisture content and also flowering and fruiting in subalpine plants correlate ambient temperature.