Physiological and Biochemical Basis of Growth Suppressive and Growth Promotory Effect of Trichoderma Strains on Tomato Plants

Abstract

Trichoderma harzianum is being used in many part of world for controlling many fungal soil borne pathogens. Plant growth responses using T. harzianum has been demonstrated in many crops. However, the mechanism through which the plant growth is influenced has not been worked in detail. Therefore an effort was made to evaluate the role of metabolic enzymes in plant growth promotion/suppression. Five isolates of T. harzianum were evaluated for growth promotory or suppressive effect on tomato plants in glass house trials. Some strains T7, T26, T31, T35, and T38 of T. harzianum increased leaf area, fresh shoot weight and root weight but some strains T13, T19, and T23 decreased shoot and root weight in comparison with untreated control plants. This promotory and suppressive effect has also been observed with the help of respiratory enzymes succinate dehydrogenase and glucose-6-phosphate dehydrogenase which are the regulatory enzyme of TCA cycle and HMP pathways. Strains T7, T31, T38, T35 and T26 of T. harzianum increased the activity of glucose 6-phosphate dehydrogenase and succinate dehydrogenase where as few strains T23, T19 and T13 decreased the activity of both enzymes. This variation in the activity of both enzymes indicated that T. harzianum plays an important role in plant growth of tomato.