Trichoderma harzianum Rifai as a biocontrol of Fusarium circinatum Nirenberg & O´Donnell in seedlings of Pinus greggii Engelm. ex Parl. in three substrates

Introduction: Damping-off is a common disease in forest nurseries that causes significant economic losses worldwide.  Objective: To evaluate the pathogenicity and incidence of Fusarium circinatum Nirenberg & O´Donnell in seedlings of Pinus greggii Engelm. ex Parl., and the use of Trichoderma harzianum Rifai as a biocontrol in three substrates.  Materials and methods: The phytopathogenic fungus F. circinatum (strain SF5) and the antagonist T. harzianum (commercial strain T-22 KRL-AG2) were inoculated into P. greggii.  Three substrates based on peat moss, pine sawdust and pine bark were used. The incidence of the disease and the morphological indices of the plant (stem diameter, height, aerial dry weight/root dry weight ratio, slenderness index and Dickson quality index) were evaluated. The data were subjected to an analysis of variance (GLM procedure of SAS version 9.0) and Tukey's multiple comparison test (P ≤ 0.05).  Results and discussion: Pathogenicity was tested using Koch's postulates. The incidence of the disease was high (> 93 %) in substrates based on peat moss and pine bark, and was lower in the sawdust-based substrate (78 %). Trichoderma harzianum and the sawdust-based substrate reduced the incidence to 66 %. Plant quality, based on the morphological indices, was highest in the peat moss substrate. Conclusion: Fusarium circinatum is pathogenic in P. greggii; the sawdust-based substrate and T. harzianum reduced the incidence of the disease in the seedlings.