Evaluation of the effect of chitin-rich residues on the chitinolytic activity of Trichoderma harzianum: In vitro and greenhouse nursery experiments

The chitin-rich residues obtained from several industries have numerous applications in diverse fields such as biotechnology, pharmacology, medicine and agriculture. In this study, three different chitin-rich residues were evaluated with regard to enhancement of the chitinolytic activity of the mycoparasitic fungus Trichoderma harzianum, used for biological control of Fusarium oxysporum in greenhouse nurseries. Chitosan (CHIT), shrimp shell powder (SSP) and mushroom wastes (MW) activated the expression of the T. harzianum genes encoding the NAGase and chitinase activities (exc1. exc2, chit42, chit33 and chit37), the highest in vitro activities of T. harzianum being seen with MW. Under greenhouse nursery conditions, the treatments involving amendment with these residues and with T. harzianum increased the NAGase activity (between 5- and 20-times higher than peat) and the chitinase activity (between 3- and 6-times higher than peat) of the growing media and maintained the shoot dry weight of plants infected with F. oxysporum. Moreover, the incorporation of these residues into the growing media enhanced the growth (first leaf length, stem length and shoot dry weight) of muskmelon seedlings. The use of these residues with T. harzianum as amendments of growing media enhanced the growth of muskmelon seedlings and decreased the weight loss due to the pathogen, giving an added-value to these residues and enhancing their management. (C) 2012 Elsevier Inc. All rights reserved.