The common bean (Phaseolus vulgaris L.) is one of the most important food legume crops worldwide that is affected by phytopathogenic fungi such as Rhizoctonia solani. Biological control represents an effective alternative method for the use of conventional synthetic chemical pesticides for crop protection. Trichoderma spp. have been successfully used in agriculture both to control fungal diseases and to promote plant growth. The response of the plant to the invasion of fungi activates defensive resistance responses by inducing the expression of genes and producing secondary metabolites. The purpose of this work was to analyze the changes in the bean metabolome that occur during its interaction with pathogenic (R. solani) and antagonistic (T. velutinum) fungi. In this work, 216 compounds were characterized by liquid chromatography mass spectrometry (LC-MS) analysis but only 36 were noted as significantly different in the interaction in comparison to control plants and they were tentatively characterized. These compounds were classified as: two amino acids, three peptides, one carbohydrate, one glycoside, one fatty acid, two lipids, 17 flavonoids, four phenols and four terpenes. This work is the first attempt to determine how the presence of T. velutinum and/or R. solani affect the defense response of bean plants using untargeted metabolomics analysis.

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Xylotrechus arvicola (Olivier) (Coleoptera: Cerambycidae) is an important pest in vineyards (Vitis vinifera) in the main wine-producing regions of Spain. Effective control of this pest is difficult due to the biology of this pest. Biological control agents (BCAs) have proven to be an effective tool in controlling and preventing the spread of a variety of plant pests and diseases. Consequently, the aim of the present study was to assess the capacity of different Trichodema spp., isolated from various vineyards and one commercial isolate of Beauveria bassiana Vuillemin (Hypocreales: Cordycipitaceae), as BCAs of X. arvicola. Isolates of Trichoderma spp. and one isolate of B. bassiana were evaluated against X. arvicola eggs, larvae and adults. Trichoderma harzianum and Trichoderma gamsii demonstrated a good ovicidal control, 100.0% with T. harzianum and over 92.0% with T. gamsii. These Trichoderma strains achieved an over 65.0% larval mortality and 87.5% adult mortality. B. bassiana was the most effective treatment against X. arvicola larvae. These results confirm that Trichoderma spp. can be used to inhibit egg development. In addition, Trichoderma spp. and B. bassiana can help to prevent larvae boring into vines and to kill adults. Therefore, Trichoderma spp., especially T. harzianum and T. gamsii, and B. bassiana can be considered as highly effective BCAs of X. arvicola in vineyards.

The interest in the study of microbiological interactions mediated by volatile organic compounds (VOCs) has steadily increased in the last few years. Nevertheless, most assays still rely on the use of non-specific materials. We present a new tool, the volatile organic compound chamber (VOC chamber), specifically designed to perform these experiments. The novel devices were tested using four Trichoderma strains against Fusarium oxysporum and Rhizoctonia solani. We demonstrate that VOC chambers provide higher sensitivity and selectivity between treatments and higher homogeneity of results than the traditional method. VOC chambers are also able to test both vented and non-vented conditions. We prove that ventilation plays a very important role regarding volatile interactions, up to the point that some growth-inhibitory effects observed in closed environments switch to promoting ones when tested in vented conditions. This promoting activity seems to be related to the accumulation of squalene by T. harzianum. The VOC chambers proved to be an easy, homogeneous, flexible, and repeatable method, able to better select microorganisms with high biocontrol activity and to guide the future identification of new bioactive VOCs and their role in microbial interactions.