Communities of Fungi in Black Cherry Stumps and Effects of Herbicide

Responses of Fungal Assembly and Co-Occurrence Network of Rhizosphere Soil to Amaranthus palmeri Invasion in Northern China

The interaction between invasive plants and soil microbial communities is critical for plant establishment. However, little is known about the assembly and co-occurrence patterns of fungal communities in the rhizosphere soil of Amaranthus palmeri. The soil fungal communities and co-occurrence networks were investigated in 22 invaded patches and 22 native patches using high-throughput Illumina sequencing. Despite having little effect on alpha diversity, plant invasion significantly altered the composition of the soil fungal community (ANOSIM, p < 0.05). Fungal taxa associated with plant invasion were identified using linear discriminant analysis effect size (LEfSe). In the rhizosphere soil of A. palmeri, Basidiomycota was significantly enriched, while Ascomycota and Glomeromycota were significantly reduced when compared to native plants. At the genus level, the invasion of A. palmeri dramatically increased the abundance of beneficial fungi and potential antagonists such as Dioszegia, Tilletiopsis, Colacogloea, and Chaetomium, while it significantly decreased the abundance of pathogenic fungi such as Alternaria and Phaeosphaeria. Plant invasion reduced the average degree and average path length, and increased the modularity value, resulting in a less complex but more effective and stable network. Our findings improved the knowledge of the soil fungal communities, network co-occurrence patterns, and keystone taxa in A. palmeri-invaded ecosystems.

Microbe Related Chemical Signalling and Its Application in Agriculture

The agriculture sector has been put under tremendous strain by the world’s growing population. The use of fertilizers and pesticides in conventional farming has had a negative impact on the environment and human health. Sustainable agriculture attempts to maintain productivity, while protecting the environment and feeding the global population. The importance of soil-dwelling microbial populations in overcoming these issues cannot be overstated. Various processes such as rhizospheric competence, antibiosis, release of enzymes, and induction of systemic resistance in host plants are all used by microbes to influence plant-microbe interactions. These processes are largely founded on chemical signalling. Producing, releasing, detecting, and responding to chemicals are all part of chemical signalling. Different microbes released distinct sorts of chemical signal molecules which interacts with the environment and hosts. Microbial chemicals affect symbiosis, virulence, competence, conjugation, antibiotic production, motility, sporulation, and biofilm growth, to name a few. We present an in-depth overview of chemical signalling between bacteria-bacteria, bacteria-fungi, and plant-microbe and the diverse roles played by these compounds in plant microbe interactions. These compounds’ current and potential uses and significance in agriculture have been highlighted.

Comparative Efficacy of Chondrosterum purpureum and Chemical Herbicides for Control of Resprouts in Tanoak and Bay Laurel

The invasive Oomycete pathogen Phytophthora ramorum has killed millions of susceptible oak and tanoak trees in California and southern Oregon forests and is responsible for losses in revenue to the nursery industry through mitigation activities. In addition, infestation of forests in the United Kingdom by this organism has resulted in the destruction of many hectares of larch plantations. Resprouting stumps can be a reservoir for the inoculum of P. ramorum persisting on a site. In areas where the application of herbicides is not permitted, a biocontrol treatment would be an indispensable alternative. Treatment of stumps with the sap-rotting fungus Chondrostereum purpureum (Pers.) Pouzar has been shown to be an effective tool for the suppression of resprouting on several species, most notably red alder. In this project, the ability of C. purpureum to suppress resprouting was evaluated on stumps of two host species, tanoak (Notholithocarpus densiflorus) and California bay laurel (Umbellularia californica). Laboratory testing of three California isolates of C. purpureum indicated that the fungus can colonize bay laurel stems. Field trials were established near Brookings, Oregon, on tanoak and on bay laurel near Soquel, California. Early results of field testing showed that C. purpureum was able to colonize the stumps of tanoak following treatment and was found to occur naturally on tanoak logs and stumps. Formulations of C. purpureum appear to have some effect on reducing sprout survival in tanoak, but the most effective and rapid treatment for this host is the hack and squirt method of applying the herbicide imazapyr. Sprayed herbicide prevents sprouting on bay laurel, and there was evidence that resprouting was inhibited on stumps treated with C. purpureum. Over time, applications of C. purpureum may be a more permanent solution as the stumps begin to decay.