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Trichoderma viride and Trichoderma harzianum strains were isolated from healthy tomato rhizosphere for evaluating their comparative bio-control potential against damping-off and root-rot diseases of tomato, caused by Pythium aphanidermatum and Rizoctonia solani respectively. Bio-control efficacy of fly-ash based Trichoderma formulations was studied under greenhouse conditions on seed germination, plant height, plant biomass, damping off and root-rot disease in tomato. Seed treatment with both the formulations significantly enhanced the seed germination, plant height and plant biomass and reduced the damping off as well as root-rot compared to control, where as Trichoderma harzianum formulation was more effective than Trichoderma viride in this reference.
An integrated approach for management of damping-off and root rot diseases using seed and soil application of Trichoderma viride and Trichoderma harzianum coupled with soil application of amendments with poultry manure/FYM was further evaluated under field condition where damping-off and root-rot incidence was reduced up to 90% and 84% respectively.
The development of scientific agriculture by man and development of plant disease by pathogens have been on parallel lines since the very beginning of crop evolution. Today when human population is crossing its limits, yield loses due to plant disease is posing serious problems before farmers, scientist and administrators.
The shortage of food in the world compels agriculture to increase production. Maximizing of yield can be achieved only if along with ensured fertilizers, irrigation and seeds of high yielding varieties, there is also provision for protection of the crop against its enemies. Plant disease contributes 13-20% losses in crop production worldwide. If this huge loss could be prevented there should be no food shortage.
The control of soil-borne disease particularly damping-off and root-rot etc has always been a problem. Soil-borne diseases always had impact on growth and productivity of crops. Species of Pythium, Fusarium, Rhizoctonia, Verticullium and Sclerotium are some of the important soil-borne fungal pathogens which cause some damage in crop plants resulting huge economic loss. Pythium spp. cause damping off and seed rot of young seedlings of all cultivated crops. In India, damage is mostly during summer and rainy seasons, both in glass house and open filed in nursery. Rhizoctonia solani is one of the most destructive plant pathogens, causes various maladies starting from root and stem rot, damping-off seed decay and several other diseases. Damping off and root-rot caused by Pythum spp, Rhizoctonia and other pathogens, which affect, the seedlings, which turn role green, and brownish lesion was found at the based portion of the stem (Manoranjitham et al., 2001).
Trichoderma spp. is saprophytic fungi which are widely distributed all over the world in soil. Trichoderma spp. has been reported and indicated to have antagonistic properties against several soil-borne fungal pathogens and thus holds promise as biological control agent (Rehman et al., 2003).
Control of plant diseases by chemicals can be spectacular but this is relatively a short term and more over, the accumulation of the harmful chemical residues some times causes serious ecological problem especially in the soil and aquatic ecosystem and to reduce their inherent hazards to plant and animal life. In recent years, the increasing use of potentially hazardous pesticides and fungicides in agriculture has been the result of growing concern of both environmentalist and public health authorities.
On the other hand biological methods can be economical, long lasting and free from residual side effects. The main purpose of the biological control of the plant disease is to suppress the inoculums load of the target pathogen to a level, which would not cause potential economic loss in a crop.
Fly-ash which is being generated in large quantity in thermal power stations, generally recognized as waste and as environmental hazard, has been reported to promote crop growth in various trials conducted under National Fly-ash Utilization Programs (Kumar et al., 1999).
In India, large quantities of fly ash are being generated, as most of our energy demand is met through coal based thermal power stations. The fly ash generation is expected to grow further as coal would continue to remain as major source of energy at least for next 25 years. The fly ash, which is a resource material, if not managed well, may pose environmental challenges. Fly-ash Utilization Program (FAUP) has been undertaking various projects/activities for technology development/ demonstration, disseminating the information, creating awareness, facilitating multiplier effects, providing inputs for policy interventions etc. in the area of safe management & gainful utilization of fly ash (FAUP, DST, New Delhi, 2007).
MATERIAL AND METHODS
The present studies were conducted in the Referral Laboratory of the Department of Allahabad Agricultural Institute - Deemed University, Allahabad, U.P. India during February, 2007 to April, 2008.
Isolation of Trichoderma spp.:
Trichoderma viride and Trichoderma harzianum strain was isolated from healthy tomato (Lycopersicum esculentum L) rhizosphere plant on Trichoderma Selective Medium (TSM) Agar using soil dilution methodology (Aneja, 2002).
Multiplication of Trichoderma spp.:
Trichoderma viride and Trichoderma harzianum strains was multiplied on pre-soaked and autoclaved sorghum (Sorghum vulgare) grains. A disc (5 mm) of actively growing culture were placed in conical flask containing autoclaved moistened ground sorghum grains and incubated for 12-15 days at 25oC.
Bio-formulation of Trichoderma spp.:
Trichoderma viride and Trichoderma harzianum cultures were air dried ground and passed through 50 to 80 mesh size sieves simultaneously to obtained pure spore powder. The commercial formulation was prepared by mixing this powder with sterilized fly-ash under aseptic condition in 1:2 (W/W) ratio of culture and powder. Fly ash 300 mesh was obtained from Unchahar thermal power station. Moisture content of 10 - 12% was maintained. Carboxy methyl cellulose (CMC) @ 0.5 % (W/W) was added as sticker / stabilizer (Kumar & Gupta, 2008)
Bio-efficacy of Trichoderma spp:
To evaluate the bio-efficacy of formulation, surface sterilized tomato (Lycopersicum esculentum L) seeds were treated with suspension of formulation consisting of 10 g six months old formulation + 10 g farm yard manure (FYM) + 0.5 g gum arabic in 50 ml sterile water per 1 kg seed with respective formulation and sown in small field in green house condition, maintaining 5 replicates of each treatment with one set of untreated control (Zaidi and Singh, 2004).
Observations were recorded on percentage seed germination after 30 DAS, plant height, plant biomass, incidence of damping off and root rot per plant at 45 DAS. The results of trials are included in table 1.
The data obtained were analyzed statistically by using two-ways classification Randomized Block Design (Analysis of Variance) for drawing conclusions from the data. The calculated value was compared with tabulated value at 5% level of probability (Chandel, 2006)
RESULTS AND DISCUSSION
The results on bio-efficacy studies included in table - 1 and figure - 1 showed that percentage seed germination, plant height and plant biomass was significantly more in all Trichoderma formulations as compared to untreated control. All the parameters were significantly more in Trichoderma harzianam alone formulation compared to Trichoderma viride alone and T. harzianam: T. viride (1:1) formulation. The order was:
T3 = T. harzianam alone > T2 = T. harzianam: T. viride (1:1) > T1 = T. viride alone > To = control.
The damping-off and root rot incidence in tomato was significantly decreased in Trichoderma bio-primed seeds in all the treatments when compared with control. Minimum disease severity of 12.20 % was recorded in T2 (T. harzianam alone) followed by T3 (14.25 %), T1 (15.90 %) and T0 (control) (28.50%) where as Trichoderma harzianum formulation was more effective than Trichoderma viride in this reference.
Table - 1. Bio-efficacy of various treatments on tomato:
% incidence of damping off
of root rot
To = control
T1 = T. viride
T2 =T. harzianum
T3 =T. viride+ T. harzianum (1 :1)
Seed treatment with Trichoderma viride formulation recorded 83 to 87% seed germination. This observation is in agreement with earlier reports. Kumar & Gupta (2008) observed 83% seed germination in T. viride treatments. Zaidi and Singh (2004) reported that Trichoderma application enhanced the seed germination, plant height and plant biomass under glass house condition in tomato.
In present study, the seed treatment with Trichoderma viride formulation in all the three formulations reduced the incidence of damping off tomato up to 88% and also enhanced the plant height and plant biomass under green house condition. Kumar & Gupta (2008) reported fly-ash based T. viride formulations increased root and shoot length, dry weight and plant height in tomato and reduced damping off up to 86%. Jayaraj et al. (2006) observed similar results and reported that seed treatment with Trichoderma formulation reduced the incidence of damping off diseases in tomato up to 74% and also enhanced the plant biomass and reduce root rot. Gnanavel and Jayaraj (2003) reported that Trichoderma viride reduced damping off diseases up to 75.23% over control in tomato. Manoranjitham et al. (2001) reported that T. viride damping off of tomato was reduced and the root length, shoot length and plant biomass in tomato seed lings was increased.
A reduction in damping off disease was observed in the present study by Trichoderma viride over control. This report is an agreement with other reports. Rehman et al. (2003) reported that the damping off disease in tomato can be effectively controlled by seed treatments followed by soil application with Trichoderma. Yehia et al. (1981) observed significantly reduced damping off disease and increased seedling survival in tomato by Trichoderma viride.