First record of Fusarium brachygibbosum as a causal agent of seed decay and damping-off disease on cotton in Iraq and Control using some bioagents

The results of the isolation and identification of pathogens accompanying the symptomatic seeds and seedlings of cotton showed that the most common fungus was Fusarium brachygibbosum. Molecular identification of the studied fungus was performed using the universal primers: the results of the genetic analysis revealed the identities of the fungus as follows: a 100% identity for F. brachygibbosum that was deposited at the GenBank under accession number ON738702.1. This fungus has shown high pathogenicity against cotton seeds and seedlings by severely reducing their Germination and growth and treating cotton seeds with the biological factors of Trichoderma spp. It revealed a high efficiency in reducing disease incidence and increasing cotton germination percentage. Trichoderma viride showed the highest ability to increase seed germination to 94.44%. In comparison, the lowest ability reached 77.77 % in Trichoderma pseudokoningii and Trichoderma reesei—the results of extracting toxins from the filters of Trichoderma spp. The study's use of trichodermin and Gliotoxin showed the presence of trichodermin and Gliotoxin in large quantities. The percentage of toxin inhibition was significant against the growth of pathogenic fungi. The highest percentage of inhibition was 86.1% for the isolate Trichoderma koningiopsis, and the lowest percentage was 66.65% for the isolate Trichoderma reesei. As for the effect of isolates of resistant fungus on the Pathogen in the field, the highest germination rate was 100%, and the inhibition rate was 0.00% when using the biological preparation prepared from the isolates (T. viride, T. pseudokoningii, T. koningiopsis and T. reesei). Keywords: Fusarium brachygibbosum; Trichoderma spp.; Trichodermin; gliotoxin; Biological control.