Final Report Summary - BIOREGENT (Biocontrol and Bioremediation agents and their role in Agriculture and Forest health) A summary description of the project objectivesThis action has contributed to the establishment of a small network of scientists from both the EU and Canada, focused on developing a more detailed fundamental understanding of how certain beneficial soil bacteria and fungi can facilitate the growth and development of plants. Concomitant with understanding the mechanisms involved in the microbial promotion of plant and tree growth, members of the network are developing and testing schemes that are of practical (and possibly also commercial) interest in agriculture, horticultural, silviculture and environmental cleanup (i.e. phytoremediation). Specifically, we are 1) evaluating the ability of antagonistic bacteria to prevent fungal infection of pine and spruce seedlings; 2) assessing the role of bacterial indoleacetic acid, a plant hormone, in the protection of crops against drought stress; A description of the work performed since the beginning of the projectSeveral plant growth-promoting bacteria were evaluated in this research for their ability to promote growth of a variety of plant species and to protect them against various biotic and abiotic stresses, including strains from the culture collections of the EU and Canadian researchers and native soil isolates. Bacteria isolated from native soils have the best chance of protecting plants as they are adapted to the soil conditions and therefore can compete effectively with other microbes. Studies using biocontrol bacteria to mitigate the damage of fungal pathogens in forest ecosystems were performed in Neiker. The impact of damage by the main forest pathogenic fungi (defoliators, canker producer and root rot fungi) was surveyed and a collection of several pathogenic fungal strains is now available to study the application of biocontrol and bioremediation agents in forest health. The most damaging forest fungal pathogens (Fusarium circinatum, Diplodia pinea, Heterobasidion annosum, Armilaria mellea, Neofusicoccum parvum, and Dothisroma spp.) are represented in this collection. In addition to Canadian biocontrol bacteria, several new bacterial isolates were tested as biological control agents to protect seedlings against these pathogens (Neiker and UNB). From a total of 100 different bacteria isolated from the roots of a healthy tree (Pinus radiata) in a forest in the Basque Country that is infected with the fungi H. annosum and A. mellea, five show good antagonism against these pathogens as well as F. circinatum. Ten experiments were conducted by UNB and Neiker to evaluate the effectiveness of these organisms as plant growth-promoting and biocontrol agents in trees under laboratory and greenhouse conditions. Strains were identified that enhanced the development of root system of Pinus seedlings, and exhibited biocontrol activity under controlled greenhouse conditions. In addition, assays were developed to measure infection levels of both H. annosum (using quantitative PCR) and the biocontrol bacteria (using GFP-tagged strains) on seedlings. This facilitates assessment of the anti-fungal activity of the biocontrol treatment and measurement of the survival rates of the biocontrol bacteria.Paenibacillus polymyxa A26 strain was shown to be effective against F. circinatum under controlled conditions (SLU NEIKER). A26 antibiotic production mutant was constructed and studies will be continued under biological settingsIn relation to the use of plant growth-promoting bacteria and mycorrizhae to remediate soils contaminated with metals, organic compounds and salt, the activity, UPO has been focused on the study of microbial populations of a polluted site, in which phytoremediation experiments have been carried out, using poplars as accumulator plants. The physiological characterization of the bacterial strains identified as Flavobacterium spp., C. soldanellicola and V. paradoxus as well as the assessment of the effects induced by these strains on poplar plants cultivated in Cu or Zn polluted soil were evaluated and have provided further insight on the role of these microbial species in promoting plant growth under stressful conditions.UNB and SLU aimed to determine the mechanism by which soil bacteria enhance drought tolerance of agriculturally important crops. Specifically, the role of indoleacetic acid produced by AzP2, a pine endophyte that was shown to protect wheat plants from drought stress, was investigated. A homologue of the gene encoding indolepyruvate decarboxylase, a key enzyme in indoleacetic acid biosynthesis, was identified in AzP2, as well as a predicted regulator. A system to generate AzP2 knockout mutants in both the indoleacetic acid biosynthetic and regulatory genes was constructed. The effect of mutant and wild-type strains will be assessed using winter wheat (T. aestivum L.) as a model plant under drought stress and non-stress condiditons.The performed work in connection with the use of plant growth promoting bacteria (PGPB) to facilitate the growth of chickpeas by UE and UW, indicate that the production of ACC deaminase under free living conditions by Mesorhizobium strains increases the nodulation, plant growth abilities and biocontrol potential of these strains, obtaining Mesorhizobium strains with high ACC deaminase activity is a matter of extreme importance for the development of inoculants for field applications. UE and UW investigated the use of plant growth promoting bacteria (PGPB) to promote the growth of legume plants, namely chickpea. A large collection of Portuguese chickpea rhizobia was screened for common plant growth promoting mechanisms. The expression of an exogenous 1-aminocyclopropane-1-carboxylate deaminase gene in Mesorhizobium strains enhanced their plant growth-promotion abilities and reduced the negative effects from abiotic and biotic stress conditions, such as salinity and other soil constraints, in chickpea plants. The use of rhizobial strains with enhanced ACC deaminase activity may contribute for developing microbial inocula for agricultural purposes. UE and UW investigated the use of PGPB in the control of the pine wilt disease nematode, Bursaphelencus xylophilus, responsible for the devastation of pine forests worldwide and a recent threat to Europe. This was the first report on the use of an ACC deaminase-producing bacterium (Pseudomonas putida UW4) as a potential biological control agent for a tree disease. Furthermore, the characterization of the bacterial community associated with B. xylophilus showed that some of these bacteria likely play an active role with B. xylophilus in the development of the pine wilt disease.The main results achieved in the project:# Canadian and New European strains with potential as plant growth promoting bacteria (PGPB) and biological control agents to improve the health of natural plant/tree ecosystems and to increase agricultural and silvicultural capacity.# Plant growth promoting bacteria (PGPB), to facilitate the growth of chickpea plants under stress conditions Mesorhizobium strains).# New microbial species with potential promoting plant growth under stressful conditions of soils contaminated (Flavobacterium spp., and V. Paradoxus).# Strain collection of fungal pathogenic (Fusarium circinatum, Heterobasidion annosum, Armilaria mellea, Diplodia pinea, Neofusicoccum parvum Dothisroma septosporosa) and micorrizhal species, characterized populations of F. circinatum, Heterobasidion annosum, Armilaria mellea, Diplodia pinea) tested pathogenicity (Fusarium circinatum, Diplodia pinea and Neofusicoccum parvum). Evaluation of isolates has also been carried out, including predisposal factors with influence in disease outbreaks (Fusarium circinatum and Diplodia pinea) .# Development of molecular protocols to quantify the beneficial and pathogenic organisms on host plants, and to measure biocontrol and plant growth-enhancing activity, including expression of specific genes.# Experimental plots to applied final proposal guidelines with epidemiological studies, 10 plots in forest ecosystems, native forest and plantations, mediterranean and eurosiberian zones are represented.# Knowledge of the mechanism by which soil bacteria enhance drought tolerance of agriculturally important crops. Specifically, the role of bacterial IAA in protecting plants from drought stress Some of the final results and their potential impact and use are# To understand how soil bacteria and fungi contribute to plant health and growth# To develop new PGPR strains with enhanced capabilities# To create an interactive network of scientists in Canada and the EU to develop the use of plant growth-promoting bacteria to facilitate environmental cleanup and sustainable chemical-free agriculture, horticulture and silviculture.# To improve the health of natural plant/tree ecosystems# To increase agricultural and silvicultural capacity# To decrease dependency on chemicals used as fertilizers, pesticides and herbicides# To understand the genetic and biochemical mechanisms used by soil microorganisms to directly promote plant growth and to control plant pathogens# To implement the European laws (based on Council Directive 91/414/EEC) related to the restriction in the use of pesticides, which are becoming more rigorous in terms of their application and use, the final proposal of which is the preservation of the environment and protection of human health.# To reduce the effect of soil contamination caused by the overuse of heavy metals, organic compounds and salts in natural ecosystems and plantations.# To reduce the negative effects of flooding and draught caused by climate change on commercial and forestry crops. This will be attained through the beneficial application of the growth promoting organisms derived from this study on various commercial species and plant/tree ecosystems in general.
