Evaluation of Antagonist Activity of Trichoderma Species against Alternaria alternata Isolated from Populus deltoides

Populus deltoides is the exotic species of poplar introduced in India in late 50s and has been grown significantly in North– western states. It is one of the most important commercial tree planted in agrosilvicutural system adopted by farmers of the region. Meanwhile, it is prone to number of biotic and abiotic agents, which affects the plantations and thus depreciates its quality. Hence, to prevent the loss and manage the diseases, apart from fungicidal use biocontrol strategy has been adopted. In the present study fifteen isolates of Alternaria alternata has been tested against Trichoderma harzianum and Trichoderma viride. Both the antagonists were at par in suppressing the fungal growth and did not achieve the significant level of inhibition. T. harzianum could be shown as better biocontrol agent than the latter owing to the percent growth inhibition shown by the isolates. Key-wordsPopulus deltoides, Alternaria alternata, Biocontrol, Growth suppression INTRODUCTION Poplars are among the leading commercial tree species of the world in view of their rapid growth and suitability for extensive range of products. They contribute significantly to some national and regional wood markets [1] and also serve as a substantial source of farm income in some countries [2]. Six indigenous (P. alba, P. ciliata, P. euphratica, P. gamblei, P. glauca and P. suvolensis [3]; and three exotic (P. deltoides, P. nigra and their hybrid, P. x. eumericana [4] ; species of poplars are reported in India. Poplars suffer from various diseases owing to its monoculture plantations. Incidence of Alternaria alternata causing leaf spot was predominant on clones of P. deltoides during 2010-2012 in the nurseries of WIMCO seedlings. Disease problems have, therefore, posed the question regarding the overuse of single clones and use of large monoclonal plantations [5]. Thus to manage the outbreak of disease, besides the use of fungicides bio-control strategy is also a potential alternative. Biological control aims at managing the plant pathogenic populations at natural levels. Access this article online Quick Response Code www.ijlssr.com DOI: 10.21276/ijlssr.2017.3.3.18 It is the reduction of inoculums density of pathogens by one or more organisms, accomplished either naturally or through manipulation of the environment, host or antagonists [6]. This is an eco-friendly approach and best alternative to chemical management. Among the fungal biocontrol agents, Trichoderma is one of the most commonly used organisms for the control of soil borne fungal pathogens and considered as effective antagonist against plant pathogenic fungi [7-9]. MATERIALS AND METHODS Total 15 isolates of A. alternata obtained from different commercial clones of P. deltoides (G48, WSL22, WSL39 and Udai) were tested against two Trichoderma species, viz., T. harzianum and T. viride (antagonists) in 2012. The cultures of antagonists were obtained from Forest Pathology Division, Forest Pathology Division, Dehradun, India. In-vitro biological activity of antagonists on A. alternata was investigated on the potato dextrose agar (PDA) using Dual Culture Method [10]. The experiment was conducted in triplicates. The control plates were also maintained in which a colony of test fungus was placed on one end of the Petri plate, while in experimental plates a colony of test fungus was placed on one end and antagonist colony at other end parallel to each other. The plates were incubated in BOD incubator at 27 ±1oC till the test pathogen attains maximum radial growth in the control plates. Radial growth of A. alternata isolates were recorded and percent inhibition was calculated using the formula [11]. ARTICLE RESEARCH Int. J. Life. Sci. Scienti. Res. MAY 2017 Copyright © 2015-2017| IJLSSR by Society for Scientific Research is under a CC BY-NC 4.0 International License Page 1071 Percentage inhibition (I) = (Control (C) – treatment (T) / Control) x100 I = C-T × 100 C Data was analyzed with the help of GENSTAT 5 Release 3.22. Two-way analysis was used for biocontrol sensitivity data. Treatments means were compared at 5 percent level of significance. RESULTS AND DISCUSSION The two antagonist isolates (T. harzianum and T. viride) showed different behaviour against the isolates of test pathogen, A. alternata (Table1 & Fig.1.). Irrespective of antagonists, maximum and significantly high antagonists’ efficiency was observed against isolate number A51 (45.9%) which was at par with isolate No. A12 (44.5%), while significantly low value was registered for isolate No. A15 (24.4%). Both the Trichoderma species expressed significantly different suppression of the growth of pathogen (33.4 and 35.0% by T. viride and T. harzianum, respectively) when pathogenic isolates were ignored. On studying the interactions between pathogen and antagonist (P x A), significantly high growth suppression was achieved for isolate No. A12 (49.7%) by T. viride. Whereas, minimum and significantly less growth inhibition was seen for isolate No. A25 (19.4%) by T. harzianum. Eight isolates, No. A7 (35.1%), A13 (39.4%), A16 (44.4%), A41 (44.7%), A47 (47.0%), A51 (48.6%), A52 (38.7%), A65 (38.0%) had maximum growth suppression by T. harzianum. While, remaining seven isolates, No. A12, A15, A24, A25, A32, A40 and A64 (49.7%, 25.8%, 29.8%, 31.8%, 32.7%, 45.9% & 44.4% respectively) were inhibited maximally by T. viride. Table1. Efficacy of Trichoderma species against A. alternata isolates Isolate No. Antagonist/Growth inhibition (%) Mean T. harzianum T. viride