Abstract
Early blight disease in Lycopersicon esculentum (Tomato) caused by Alternaria solani is a disease posing economical threat to tomato cultivation worldwide. The efficacy of fifteen plant extracts (Polyalthia longifolia, Azadirachta indica, Datura stramonium, Ocimum sanctum, Calotropis procera, Crotalaria juncea, Eucalyptus obliqua, Cassia fistula Agele marmelos, Croton bonplonadium, Pergularia daemia, Cleome viscose, Phyllanthus amarus, Bauhinia purpurea and Euphorbia hirta), five Trichoderma harzianum strains (T1, T2, T3, T4 and T5) and seven de oiled cakes (neem cake, castor cake, karanj cake, mustard cake, groundnut cake, salmeal cake and mahua cake) were investigated in vitro and in vivo conditions. In laboratory conditions, all the treatments inhibited the mycelium of A. solani. T5 strain of Trichoderma harzianum (81%), Eucalyptus obliqua (80.7% at 15% concentration) among plant extracts and karanj cake (48.6% at 10% concentration) among de oiled cakes recorded maximum mycelium inhibition of the pathogen. Pot culture experiments were further conducted to check the combined effect of selected plant extracts and de oiled cakes (from laboratory conditions) with Trichoderma harzianum. All the three compatible constituents were further evaluated in the field conditions. The combination of T5 + Eucalyptus obliqua + karanj cake recorded maximum inhibition of (59.8%) against A. solani and was comparable with fungicide mancozeb (71.8%). Foliar spray application of tomato plants with all the combined constituents has significantly reduced the early blight infection as compared to untreated control. Thus, it could be concluded that the synergistic effect of combined constituents may be an efficacious treatment against Alternaria solani as an invulnerable option to synthetic agrochemicals.
Highlights
Blight disease of tomato is caused by Alternaria solani has consistently been one of the utmost constraints in the tomato production
In the present investigation evaluation of Trichoderma harzianum strains in combination with both plant extracts and de oiled cakes was undertaken to determine their effects on early blight disease in green house conditions
All the five isolates of Trichoderma harzianum significantly inhibited the growth of A. solani (Fig 1)
Summary
Blight disease of tomato is caused by Alternaria solani has consistently been one of the utmost constraints in the tomato production. Attempts have been made to manage plant diseases using plant extracts, bio control agents and de oiled cakes separately (Ramachandran, 2006; Kakavan, 2013 and Shabana, 2016). Phenols, flavonoids, tannins and coumarins that are toxic and called natural bio pesticides (Irshad et al, 2011) These constituents serve for the systemic defense mechanisms against plant pathogens. The de oiled cakes are the residues left after the extraction of oil from the seeds of the plants They serve as exemplary substratum for the growth and development of microorganisms by providing the necessary nutrients to them and indirectly serving to boost up the systemic resistance in plants (Kumari et al, 2013). In the present investigation evaluation of Trichoderma harzianum strains in combination with both plant extracts and de oiled cakes was undertaken to determine their effects on early blight disease in green house conditions
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