Résumé:
The present investigation aimed to isolate and to identify the mycetes accompanying interior in durum wheat seed (Triticum durum Desf.) and to evaluate the in vitro antagonism capability of Trichoderma harzianum against the isolated fungi. Seed samples of durum wheat cultivars
Vitron, Waha, GTA Dur and Cirta were made available by the cereal and dry legumes cooperative of Oum-El-Bouaghi (Algeria). First year results allowed the identification of 93 isolates from GTA Dur, Waha and Vitron genotypes. Most frequents genus were, in that order,
Alternaria, Cladosporium and Fusarium. 83 isolates were identified in second year from Waha, Vitron and Cirta from which Alternaria were the most frequent genera and Fusarium acuminatum. 129 isolates were found the third year from GTA Dur Waha, Vitron and Cirta, with
Alternaria, as the most frequent genera, Fusarium, Stemphylium botryosum, Cladosporium sp , and Botrytis cinerea. The results of the in vitro study of the antagonistic ability of T.harzianum,against the isolated fungi, indicated the inhibition of mycelium growth to variable degrees.
Microscopic observations showed that T.harzianum induced cell lyse, destroyed mycelia and spores of the tested isolates, excepted those belonging to Fusarium genus. T.harzianum produced haustoria on mycelia of tested isolates through mycoparasitism. The results of the in vitro study of remote confrontation of T.harzianum with the tested isolates, on PDA medium, suggested that volatile metabolic substances of T.harzianum reduced the growth of the various pathogenic mycetes. Microscopic observations of mycelia showed that, the volatile metabolic substances of T.harzianum induced degradation and inhibited sporulation of certain isolates compared to the non-treated checks. Seed treatment of the studied durum varieties with T.harzianum filtrate enhanced seed germination ability and stimulated seedling growth compared to untreated seed which exhibited weak growth and presented malformations. Treated seed were less infected by
the mycetes
