Groundnut (Arachis hypogaea L.) suffers from many soil borne pathogens that deteriorate the quality of the seeds and are responsible for high yield loss. Practically Trichoderma sp. is used for seed treatment, it minimizes the seed and soil borne pathogens and supports plant growth promotion activities. In the present study, five different isolates of Trichoderma spp. were isolated from groundnut (A. hypogaea ) rhizosphere soil. All the five isolates were confirmed by morphological methods and using molecular tools through Polymerase Chain Reaction (PCR) amplification of Internal Transcribed Spacer (ITS) region of Trichoderma sp. and DNA gets amplified in 650 bp to 700 bp. Trichoderma spp. were molecularly identified as T(SP)-20 (Trichoderma longibrachiatum), T(AR)-10 (T. asperellum), T(VT)-3 (T. hamatum), T(BI)-16 (T. longibrachiatum), T(TK)-23 (T. citrinoviride). Phytostimulation activities of all the six isolates viz., phosphate solubilization, Ammonia production, IAA production, and Siderophore production, were evaluated. Among the six isolates, T(SP)-20, T(AR)-10, and TNAU-TA showed higher phytostimulation activities. The growth promotion of Trichoderma spp. on groundnut was assessed through the roll towel method. The isolate T(SP)-20 (T. longibrachiatum) produced the highest germination percentage of 93.33 and vigor index of 2246.2. This work developed a new isolate of T. longibrachiatum (T(SP)-20) which is a native isolate having significant  phytostimulation and growth promotion activities and it could be exploited for other soil borne disease managing successfully.

Onions are an important vegetable crop, which is infected by many soils and foliar pathogens. Among them, Fusarium Basal Rot (FBR) causes yield losses of up to 50 per cent in the field and 30 to 40 per cent during post-harvest storage of bulbs.  For management of basal rot of onion, the efficacy of native antagonists such as six different Trichoderma sp. (T1-T6), five different Bacillus sp. (B1-B5) and five different oil cakes was assessed against the Fusarium oxysporum f.sp. cepae under in vitro condition. Among them, T3 collected from Kulithalai recorded maximum virulence as well as dark green sporulation with conidia length of 2.68–3.25 and breadth of 2.54-3.46µ. Among the tested isolates, In the case of  Bacillus sp., isolate B4 recorded the maximum inhibition zone (66.16%), followed by B. subtilis (B5), which recorded a (59.03%) inhibition on the mycelial growth. Among the five different oil cakes, the filtrates of neem cake showed a maximum inhibition zone against F. oxysporum f.sp. cepae of 1.29 cm @ 15% concentration, followed by groundnut cake at 1.36 cm @ 30% concentration. Hence the different control measures, Trichoderma sp. showed critically acclaimed performance under in vitro than others. The combined application of Trichoderma sp, Bacillus sp and neem oilcake significantly inhibited the growth of basal rot of onion due to the presence of the antimicrobial property.

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Background: Sclerotium rolfsii is a soil borne notorious pathogen widely affecting pulses, vegetables, oil seeds, flowers and ornamentals recording high yield loss. In groundnut it causes stem rot. The current study is focused towards management of S. rolfsii using combined application of Trichoderma spp. under field condition. Methods: Twenty-five isolates of Trichoderma spp. were screened initially against the stem rot pathogen through dual culture method. The effective Trichoderma spp. again assessed by agar well diffusion method and their secondary metabolites were identified using GC-MS. Result: From the 25 isolates, T. longibrachiatum and T. asperellum were inhibitory to the growth of S. rolfsii. The isolate T(SP)-20 of T. longibrachiatum showed 84.44% inhibition of mycelial growth of pathogen followed by T(AR)-10 of T. asperellum (75.55%). The major compounds present in GC-MS analysis of T. longibrachiatum and T. asperellum are 2-Tricosenoic acid (3.29%), Hexadecane (3.12%) and Phenol (27.18%), 2, 6, 10-Trimethyltridecane (3.44%) respectively. At field level combined application of effective T. longibrachiatum and T. asperellum excelled well in reducing stem rot disease incidence (82.67%) when compared to individual species.