Identification of potential marker genes forTrichoderma harzianumstrains with high antagonistic potential againstRhizoctonia solaniby a rapid subtraction hybridization approach

A rapid subtraction hybridization approach was used to isolate genes differentially expressed during mycelial contact betweenTrichoderma harzianum(Hypocrea lixii) andRhizoctonia solani, and could serve as marker genes for selection of superior biocontrol strains. Putatively positive clones were evaluated
by transcription analysis during mycelial contact withR. solaniversus growth on glucose, and for their differential transcription between two strains with either strong or poor biocontrol
capability before, at, and after contact withR. solani. Besides four clones, which had similarity to putative but as yet uncharacterized proteins, they comprised ribosomal proteins,
proteins involved in transcriptional switch and regulation, amino acid and energy catabolism, multidrug resistance, and degradation
of proteins and glucans. Transcription of three clones was evaluated in fiveT. harzianumstrains under confrontation conditions withR. solani. Two clones—acetyl-xylane esterase AXE1 and endoglucanase Cel61b—showed significant upregulation during in vivo confrontation
of aT. harzianumstrain that successively demonstrated a very high antagonistic capability towardsR. solani,while expression was progressively lower in a series ofT. harzianumstrains with intermediate to poor antagonistic activity. These clones are promising candidates for use as markers in the
screening of improvedT. harzianumbiocontrol strains.