Biodiversity of the genus Trichoderma and identification of marker genes involved in the antagonism between Trichoderma spp. and plant pathogenic fungi

As Mediterranean islands are known for their high diversity of vascular plants and a high level of endemism, they can provide basic insights into the relationship between geographical patterns and ecological processes. Studying the soil fungus Trichoderma/Hypocrea is of special interest to our working group due to its world-wide distribution, the continuos ongoing identification of new isolates, and its high percentage of strains being effective as biocontrol agents. We isolated 482 strains of Hypocrea/Trichoderma from 15 soils comprising undisturbed and disturbed soil environments. Isolates were identified at the species level by the oligonucleotide BarCode for Hypocrea/Trichoderma, sequence similarity analysis and phylogenetic inferences. The majority of the isolates were positively identified as pan- European and/or pan-global Hypocrea/Trichoderma species from Sections Trichoderma and Pachybasium. T. harzianum (H. lixii) is well known as a biocontrol agent against a range of economically important plant pathogens. In the present study we used a Rapid Subtraction Hybridisation approach to isolate genes which are differentially expressed during mycelial contact between T. harzianum and R. solani, and could serve as marker genes for selection of superior biocontrol strains. The 50 characterised clones comprised proteins involved (i) in protein synthesis and turn-over, (ii) in metabolism, and (iii) in the hydrolysis of macromolecules. An acetyl xylane esterase and an endoglucanase showed significant upregulation during in vivo confrontation of a T. harzianum strain with high antagonistic capability towards R. solani, while the expression was low or absent in a T. harzianum strain with poor antagonistic activity.