CRISPR-Cas for Fungal Genome Editing: A New Tool for the Management of Plant Diseases

Trichoderma gamsii T6085 has been investigated for many years as a beneficial isolate for use in the biocontrol of Fusarium head blight (FHB) of wheat caused primarily by Fusarium graminearum. Previous work focused on application of T6085 to wheat spikes at anthesis, whereas application to soil before or at sowing has received limited attention. In the present study, the competitive ability of T6085 on plant residues against F. graminearum was investigated. Results showed a significant reduction of wheat straw colonization by the pathogen and of the development of perithecia, not only when T6085 was applied alone but also in the presence of a F. oxysporum isolate (7121), well known as a natural competitor on wheat plant residues. T6085 was able to endophytically colonize wheat roots, resulting in internal colonization of the radical cortex area, without reaching the vascular system, as confirmed by confocal microscopy. This intimate interaction with the plant resulted in a significant increase of the expression of the plant defense-related genes PAL1 and PR1. Taken together, competitive ability, endophytic behavior, and host resistance induction represent three important traits that can be of great use in the application of T6085 against FHB not only on spikes at anthesis but potentially also in soil before or at sowing.

Trichoderma is a fungal genus comprising species used as biocontrol agents in crop plant protection and with high value for industry. The beneficial effects of these species are supported by the secondary metabolites they produce. Terpenoid compounds are key players in the interaction of Trichoderma spp. with the environment and with their fungal and plant hosts; however, most of the terpene synthase (TS) genes involved in their biosynthesis have yet not been characterized. Here, we combined comparative genomics of TSs of 21 strains belonging to 17 Trichoderma spp., and gene expression studies on TSs using T. gamsii T6085 as a model. An overview of the diversity within the TS-gene family and the regulation of TS genes is provided. We identified 15 groups of TSs, and the presence of clade-specific enzymes revealed a variety of terpenoid chemotypes evolved to cover different ecological demands. We propose that functional differentiation of gene family members is the driver for the high number of TS genes found in the genomes of Trichoderma. Expression studies provide a picture in which different TS genes are regulated in many ways, which is a strong indication of different biological functions.

Fusarium graminearum is among the main causal agents of Fusarium head blight (FHB), or scab, of wheat and other cereals, caused by a complex of Fusarium species, worldwide. Besides causing economic losses in terms of crop yield and quality, F. graminearum poses a severe threat to animal and human health. Here, we present the first draft whole-genome sequence of the mycotoxigenic Fusarium graminearum strain ITEM 124, also providing useful information for comparative genomics studies.

Plants constantly face the environment that surrounds them and fight for survival against biotic and abiotic stress factors. To deal with harmful conditions, plants have developed a multilayer defence system, making them capable of recognising threats and promptly recovering from them. This phenomenon, which takes advantage of the “memory effect”, is referred to as bio-priming and represents a new frontier in terms of crop protection. Here, we investigated the “indirect” protective mechanisms of a new yeast extract formulate in Vitis vinifera cv. Sangiovese plants at both the biochemical and genic levels. The formulate was applied once a week for three consecutive weeks, and grapevine leaves were sampled from the first to the fifth day after treatment (dat) at every week of the experiment. Increased levels of jasmonic acid (every week at 2 dat; +70% as average) and abscisic acid (at 1 dat of the first week, more than 1.7-fold higher than the control) and the underproduction of salicylic acid (from 2 dat; −18%) confirmed that these signalling molecules/”specialised compounds” are actively involved in the early activation of defence pathways in treated vines. In addition, pr2 and chit1b, two genes involved in regulating hormonal crosstalk, were significantly up-regulated (both in the first and second week of the trial) and were also found to underlie upstream molecular activation. The results obtained by this investigation confirm the use of this new product to prime and protect grapevines from a wide range of fungal and fungal-like plant pathogens through the induction of defence responses.