Liquid Formulation of Trichoderma Species for Management of Gray Mold in Castor (Ricinus communis L.) and Alternaria Leaf Blight in Sunflower (Helianthus annuus L.)

Abstract

The composition, concentration, shelf life and inconsistent performance are the major concern in formulation of bioagents in general and Trichoderma spp. in particular. To overcome some of these problems, Suspension Concentrate (SC) formulation of a potential isolates of Trichoderma viz., T. harzianum Th4dSC and consortium of T. harzianum Th4d SC and another species T .asperellum Tv5 SC were developed using conidial biomass of these bioagents produced by a production process supporting a higher quantities of biomass and viable propagules with better shelf life and persistence on sprayed surfaces. In this study, twenty five selected strains of Trichoderma were screened in vivo against foliar diseases (Alternariaster Leaf Blight (ALB) of sunflower and Botryotinia Gray Mold (BGM) of castor). Among these strains, T. harzianum Th4d and T. asperellum Tv5 were able to produce mycolytic, defense enzymes and able to control two diseases effectively. Further a study was conducted to standardize the dose of SC formulation of Trichoderma for foliar application and seed treatment. The highest antagonistic activity was achieved with concentration of 2 × 10 7 conidia/ml. The two selected strains were able to reduce severity of BGM and ALB under greenhouse conditions. In field trials (rainy season of the years 2009-10 and 2010-11), seed treatment, foliar application of T. harzianum Th4d SC at 2 ml/l and consortium formulations (T. harzianum Th4dSC+ T. asperellum Tv5SC at 1 ml/l) effectively reduced disease severity (ALB reduction up to 50-55% and BGM up to 55-65%). In addition, these applications enhanced yield of sunflower and castor compared to untreated control. Application of T. harzianum Th4dSC at 2 ml/l and consortia T. harzianum Th4dSC + T. asperellum Tv5SC at 1 ml/l showed better persistence with log CFU (colony forming unit) 7.61 and 8.45 respectively on sprayed leaves of sunflower population levels of log CFU 10.73 and 10.71 on capsules of castor at 15 days after first spray. The liquid formulations of both the strains retained good shelf life with viable spore counts of log CFU of 8.0 to 7.4 at 540 days when stored at room temperature. Thus, the efforts resulted in identification and development of suspension concentrate formulation with long shelf life of two potential Trichoderma strains for the first time for foliar disease management.