Résumé:
The aim of this study was to isolate and to identify the pathogenic fungi accompanying interior in
hard wheat seeds, and to evaluate the antagonism capability in vitro of (Trichoderma harzianum)
against those pathogenic isolated fungi. Three samples of local hard wheat seeds (Triticum
durum Desf) were brought from Oum-elbouaghi (Algeria) silos yields, follower for varieties: Vitron,
Waha, and Cirta. ).They were stored for one year. The results of isolation on potato-dextrose agar (PDA) medium and after identification of fungal accompanying interior in the seeds clarified
about (83) fungus isolates following for species next : Fusarium acuminatum (1 isolate) in a ratio
of (1.2%), and Alternaria(82 isolates) with a ratio of (98.795 %).The Alternaria isolates
apportioned among two species: Alternaria alternata with 39 isolates(12 isolates for: Alternaria
alternata1 and 27 isolates for : Alternaria alternata2) and Alternaria infectoria with 43
isolates).And, besides it was clearly seen that the Cirta variety was a lowest infected with
fungi(19 isolates) in ratio of (22.89 %), and both varieties Waha and Vitron with(32 isolates)for
each one in a ration equal (38.554 %) . The results of the antagonistic capability in vitro of
(Trichoderma harzianum) against isolated fungi, showed that: 1- The direct confrontation in vitro
of Trichoderma harzianum against the different fungus isolates on PDA medium, showed that: a In the fourth day of the experiment, Trichoderma harzianum inhibited the mycelia growth of
different pathogenic fungi in dual cultures, with different ratios, it was equal to: 6.66% for
Fusarium acuminatum, and 23%, 26.66% and 40% for Alternaria alternata1, Alternaria alternata2,
and Alternaria infectoria, respectively. b-The microscopic observations of the different interactions
hyphal between Trichoderma harzianum and different fungus isolates, showed that the
antagonistic fungus affected on Alternaria species with the decomposition phenomenon (Lyses),
where it analyzed the mycelia and spores of Alternaria altrenata2 and Alternaria infectoria, while it
analyzed the mycelia of Alternaria alternata1, compared with control. 2- The remote confrontation
in vitro of Trichoderma harzianum against the different fungus isolates on PDA medium showed
that : a- The volatile metabolic substances of Trichoderma harzianum affected the growth of the
different pathogenic fungi, with different ratios over the seven days of treatment, compared with
control.b- The microscopic observations Noted that the volatile metabolic substances of
Trichoderma harzianum affected some isolated fungi with mycelia analysis prevent the spore's
formation of the Alternaria alternata2, while stopped the spore formation of Fusarium
acuminatum, compared with control
