![]() ![]() Fumigants and fungicides cannot completely eradicate the Armillaria spp. ![]() Armillaria mellea can persist saprotrophically in roots after the death of the host and it can also spread below ground through specialised and robust structures known as rhizomorphs. Infected plants show a decline in vigour and production and generally die within a few years of infection. In particular, one of the most aggressive species ( Armillaria mellea) colonises living woody roots, causing damping off and root rot. are among the most serious plant root pathogens, and cause significant economic losses to perennials, such as fruit crops, timber and ornamental trees in boreal, temperate and tropical regions of the world. Soil phytopathogenic fungi cause severe diseases in several crops, and Armillaria spp. Molecular interplay between soil microorganisms has mainly been studied in dual cultures of plant pathogens and biocontrol agents. Despite the widespread occurrence of interspecific microbial interactions in nature and their crucial relevance, there is a lack of understanding about how each species perceives and responds to interactions with other microbes within a complex community. However, microbes have evolved strategies not only to fight each other, but in some cases relationships to adapt or support each other, increasing the overall fitness of the community. Plant pathogens have to compete with members of the rhizosphere microbiota for available nutrients and microsites in order to infect root tissue, and they are significantly restricted in growth by the antagonistic activities of biocontrol microorganisms in suppressive soils. For example, direct and indirect competition, like antagonism and nutrient consumption, have an adverse effect on interacting members of the population. These interactions can be synergistic, neutral or antagonistic, and can affect the growth, metabolism and differentiation of members of the microbial community. Microbe-microbe interactions have an important impact on microbial fitness in the soil and they can positively or negatively affect other participants, including organisms of higher taxa. ![]() Soil bacteria and fungi have undergone evolution and niche differentiation, interacting in different ways with various outcomes in soil ecosystems. Soil microorganisms are key determinants of biological soil quality, supporting soil fertility and indirectly plant health. The soil microbial community is probably the most important component of the soil biota and it is responsible for a wide range of ecologically significant functions. Global transcriptional analysis of the simplified soil microcosm revealed complex metabolic adaptation in the soil environment and specific responses to antagonistic or neutral intruders. This work represents an additional step towards understanding molecular interactions between plant pathogens and biocontrol agents within a soil ecosystem. atroviride were already activated during incubation in the simplified soil microcosm, possibly to occupy niches in a competitive ecosystem, and they were not further enhanced by the introduction of A. Moreover, activation of resistance mechanisms dominated in the simplified soil microcosm in the presence of both A. ![]() Both the phytopathogen and its biocontrol agent were specifically recognised by the simplified soil microcosm: defence reaction mechanisms and neutral adaptation processes were activated in response to competitive ( T. Pathway analysis revealed complex adaptations of soil microorganisms to the harsh conditions of the soil matrix and to reciprocal microbial competition/cooperation relationships. More than 46 million paired-end reads were obtained for each replicate and 28,309 differentially expressed genes were identified in total. ResultsĪ simplified soil microcosm containing 11 soil microorganisms was incubated with a plant root pathogen ( Armillaria mellea) and its biocontrol agent ( Trichoderma atroviride) for 24 h under controlled conditions. We used an RNA sequencing approach to elucidate the molecular interplay of a soil microbial community in response to a plant pathogen and its biocontrol agent, in order to examine the molecular patterns activated by the microorganisms. Microbial biocontrol agents have been extensively studied as alternatives for controlling phytopathogenic soil microorganisms, but molecular interactions between them have mainly been characterised in dual cultures, without taking into account the soil microbial community. Soil phytopathogenic fungi are one of the most important causes of crop losses worldwide. Soil microorganisms are key determinants of soil fertility and plant health. ![]()
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