Mycoparasitism and defense responses of Trichoderma spp. in biocontrol of Macrophomina phaseolina root rot of safflower.

Abstract

Trichoderma spp. was isolated from safflower (Carthmus tinctorills L.) rhizosphere soil and was evaluated for their mycoparasitism action, in vitro analysis for their efficacy in solubilizing the inorganic phosphorus (P) and to produce the mycolytic enzymes in liquid cultures and its ability to induce systemic resistance against root rot caused by Macrophomina phaseolina in safflower. Hyphal interaction studies were performed to study the mycoparasitism action based on in vitro dual culture studies with Trichoderma spp. against M phaseolina. Based on microscopic observations it indicates that the inhibitory effect was caused by an interaction that took place in close contact with the host hypha, causing lysing, swelling and coiling mycelia resulting potentially reduced of mycelial growth of M phaseolina. Bioagents were tested in vitro for their efficacy in solubilizing the inorganic phosphorus and to produce the mycolytic enzymes in liquid cultures. All the isolates were found to solubilize inorganic (P) and lytic enzymes activity to various extent. T harzianum (Th4d) (79.0 Ilg PI rnL), T asperellum (T73 16) (91.2 Ilg PI rnL) and Tviride (Tv 5) (50.3 Ilg PI rnL) solubilized 70% of that solubilized by the reference strain Aspergillus niger (149.7 Ilg PI mL). Chitinase (l7.7U/ml), 13-1, 3-glucanase (49.3U/ml) and 13 -1, 4-glucanase (0.95 U/m]) activities were found highest in T harzianum Th4d over other isolates. On the other hand increased activity of defense related enzymes viz., peroxidase (PO), polyphenol oxidase (PPO) and phenylalanine ammonia- lyase (PAL) activity in three potential Trichoderma spp. viz., T .harzianum (Th4d), T. viride (Tv5) and T asperellum (T73l6) pre- treated safflower plants challenged with M phaseolina was observed. Significant accumulation of PO, PPO and PAL activity at 30 days interval was high compared to 60 days in all these bioagents. Apart from these application of the Th4d reduced the incidence of root rot and enhanced the plant growth promotion to a reasonable extent against M phaseolina, which is directly correlated with the resistance of the plant against infection. Thus, from our findings it is evident that the hyphal interaction studies and the interrelationship between these enzymes playa key role to stimulate the defense mechanism which aid in disease management as well as plant growth promotion of the host plant against pathogen attack.