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Chemical fungicides used in plant disease management may have deteriorative effects on humans, animals, and the environment. The use of native strains of Trichoderma spp. against plant diseases may help to reduce the dependence on chemical fungicides. In this study, eleven novel isolates of Trichoderma spp. from virgin forest soils of different agro-climatic zones of Kerala were characterized and evaluated for their efficacy against damping off disease of tomato caused by Pythium aphanidermatum under in vitro and in vivo; and also, against wilt pathogen, Fusarium oxysporum under in vitro conditions. Dual culture assay showed that all the Trichoderma isolates were found to inhibit the growth of P. aphanidermatum and F. oxysporum under in vitro conditions with multiple modes of action. The mycelial colour, texture, and conidial characters varied among all the isolates. The volatile metabolites by isolates of Trichoderma spp. also showed in vitro inhibition of the pathogens. Seed treatment (20 g kg-1) and potting medium addition @ 2 % (w/w) of isolates TRMW-2, TRKR-2, TRPN-3, TRPN-11 and TRPN-17 could effectively reduce pre- and post-emergence damping off of tomato. Among them, isolates TRMW-2, TRKR-2, and TRPN-11 were the most effective ones in reducing pre- and post-emergence damping off to about 72 and 90 percent respectively. Molecular identification of the isolates of Trichoderma spp. using ITS universal primers revealed similarity with certain reference strains of the NCBI Genbank database. [ABSTRACT FROM AUTHOR]

Trichoderma spp. are long been recognized as efficient fungal biocontrol agents for the control of plant disease and for their ability to increase plant growth and development. Management of soil borne diseases has become very much important since it causes high crop yield losses. The present study was carried out to isolate Trichoderma spp. from soil samples collected from different locations of Kerala and to test their in vitro efficacy against soil borne pathogens viz., Pythium aphanidermatum and Rhizoctonia solani. The Trichoderma spp. was isolated on Trichoderma Selective Medium (TSM) and observed that the isolates differed in radial growth and colony characters such as colony colour, texture and sporulation. In vitro studies revealed the potential of Trichoderma isolates against soil borne pathogens. Isolates TRPN3 and TRPN7 exhibited no sporulation and white mycelial colour. Isolates which completed their growth at four days after inoculation include TRKR1, TRPN3, TRPN7, TRPN10 and TRPN18. Biocontrol activities against different pathogens resulted in inhibition of pathogens. Maximum inhibition percentage was observed by the isolates TRPN7, TRPN15 and TRKR2 against both the pathogens. The maximum inhibition exhibited against both the pathogens is due to the antagonistic property displayed by the isolates. [ABSTRACT FROM AUTHOR]

The effect of application of different biocontrol agents (Trichoderma spp (eight isolates), Pseudomonas fluorescens (four isolates) and Bacillus subtilis (two isolates)) was tested against head rot fungus, Sclerotinia sclerotiorum and root-knot nematode, Meloidogyne incognita complex diseases. In vitro studies showed that three Trichoderma isolates (Tvc1, Tvc2 and Thc) were effective in inhibition of mycelial growth of the fungus as well as egg hatching ability of the nematode. Application of talc based formulation of biocontrol agents (bioformulations) individually as well as in mixtures with or without chitin was tested against head rot-root-knot disease complex under greenhouse conditions. The combined application of bioformulation mixture (Tvc1, Tvc2 and Thc) along with chitin reduced the incidence of the complex diseases and induced significantly increased activities of phenylalanine ammonia-lyase (PAL), peroxidase (PO), polyphenol oxidase (PPO) and chitinase in cabbage. Activities of PAL and chitinase reached maximum levels within 10 - 20 d, while the activity of PAL continued to be maintained up to 40 d after the application of Tvc1 + Tvc2 + Thc + chitin. Isozyme analyses observed that unique PO (PO1, PO2 PO3 and PO4) and PPO (PPO1, PPO2 and PPO3) enzymes were induced after 10 d in cabbage plants treated with Tvc1 + Tvc2 + Thc + chitin upon challenge inoculation with head rot-root-knot pathogens. Similarly, the bioformulation mixture with chitin was successful at reducing the incidence of head rot-root-knot apart from enhancing the crop yield under field conditions. The mechanism associated with reduced incidence of head rot-root-knot in cabbage may be due to induction of defense proteins (PAL, PO, PPO and chitinase) in the crop. [ABSTRACT FROM AUTHOR]

ThePseudomonas fluorescensisolate 1 (Pf1) was found to protect the ragi [Eleusine coracana(L.) Gaertner] blast fungus,Pyricularia grisea. Induction of defense proteinsviz.chitinase,ß-1,3 glucanase, peroxidase (PO) and polyphenol oxidase (PPO) by the Pf1 isolate was studied againstP. grisea. Chitinase in a resistant, susceptible and commonly used cultivar with and without challenge inoculation ofP. grisea, revealed changes in the isoform pattern by UV illumination after staining the gel with fluorescent brightner 28. Native PAGE (polyacrylamide gel electrophoresis) of PO showed the single isoform in all the treatments including the control and a significant increase in the intensity of the band in the inoculated control and Pf1 treatment in all the varieties. Isoform analysis of PPO showed the induction of PPO inP. fluorescenstreated plants challenged withP. grisea. [ABSTRACT FROM AUTHOR]