Improvement of oilseed Brassica crops by Trichoderma use: Gene transfer and direct interaction

Global agriculture must urgently adopt a new approach to ensure adequate food production for the increasing population in the current context of adverse conditions, while prioritizing environmental sustainability. This change requires innovative and environmentally conscious methods, such as symbiotic-microorganisms-based products. Among these organisms, the genus Trichoderma stands out, as these fungal endophytes reside within many plant species including those in the Brassicaceae family and interact with them positively. Brassicaceae encompass numerous taxa of special agricultural and food interest, such as those known as oilseed brassicas (OSBs). Among these group are crops for obtaining canola and mustard seeds, commonly used for oil and spices production, respectively. OSBs are of greater interest for food because they are rich source of vitamins and minerals, and have also a great antimicrobial, antioxidant and antitumor potential application. Therefore, the improvement of these plant species (or of their cultivation methods) may ultimately lead to an improvement in human food and, accordingly, human health. This progress could go hand in hand with the Trichoderma fungal genus, either based on transgenesis with some of their genes, or using these fungi to formulate and produce bioinoculants. In relation to transgenesis, the most widely studied are those based on Trichoderma genes encoding endochitinases and Kelch-like family proteins, in both cases to achieve an antifungal effect against pathogenic fungi. With regard to Trichoderma-based products, these can be aimed at promoting plant growth, protecting crops against pathogens by acting as biological control agents (BCAs), or even reducing contaminants in the soil, such as heavy metals. The purpose of the present literature review is to analyse and discuss most of the existing studies to date on the interaction between OSB crops and Trichoderma fungi.