CHARACTERIZATION OF Trichoderma spp. BY RAPD AND BIOCONTROL ABILITY TO ROOT ROT PATHOGENS OF WATERMELON

AbstractThe present study was carried out to evaluate the effect of bioagents and organic amendments in suppressing the dry root rot of mungbean incited by Rhizoctonia bataticola. The locally isolated pathogen and fungal biocontrol agents were identified based on morphological and molecular characterization. These identified bioagents were tested in vitro, and the highest mycelial inhibition was recorded in dual culture assay by Trichoderma harzianum (74.44%), and among organic amendments, maximum mycelial inhibition was found in neem cake (61.11%). In a greenhouse study, T. harzianum + neem cake effectively enhanced the percent germination (93.33%) and decreased the percent disease mortality (11.67%) than the other treatments. The morphological parameter like plant height (57.50 cm), dry weight (22.83 g) root nodules (51), pods/plant (58), and 100-seed weight (5.78 g) were found to be at the maximum in this combined application. Physiological pigments viz. chlorophyll (2.41 mg/g) and carotenoids (0.19 mg/g), protein content (5.85 mg/g), and leghemoglobin (11.75 mg/g) were also found to be maximum in T. harzianum + neem cake and minimum phenol content (1.41 mg/g). The study concludes that T. harzianum + neem cake can be recommended as an effective approach for the management of dry root rot of mungbean.

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Molecular Characterization and Identification of Biocontrol Isolates of Trichoderma spp

Applied and Environmental Microbiology ◽

10.1128/aem.66.5.1890-1898.2000 ◽

2000 ◽

Vol 66 (5) ◽

pp. 1890-1898 ◽

Cited By ~ 126

Author(s):

M. R. Hermosa ◽

I. Grondona ◽

E. A. Iturriaga ◽

J. M. Diaz-Minguez ◽

C. Castro ◽

...

Keyword(s):

Synergistic Effects ◽

Phytopathogenic Fungi ◽

Molecular Techniques ◽

Internal Transcribed Spacers ◽

Trichoderma Spp ◽

Green Mold ◽

Phoma Betae ◽

Sequence Types ◽

Type Strains

ABSTRACT The most common biological control agents (BCAs) of the genusTrichoderma have been reported to be strains ofTrichoderma virens, T. harzianum, and T. viride. Since Trichoderma BCAs use different mechanisms of biocontrol, it is very important to explore the synergistic effects expressed by different genotypes for their practical use in agriculture. Characterization of 16 biocontrol strains, previously identified as “Trichoderma harzianum” Rifai and one biocontrol strain recognized asT. viride, was carried out using several molecular techniques. A certain degree of polymorphism was detected in hybridizations using a probe of mitochondrial DNA. Sequencing of internal transcribed spacers 1 and 2 (ITS1 and ITS2) revealed three different ITS lengths and four different sequence types. Phylogenetic analysis based on ITS1 sequences, including type strains of different species, clustered the 17 biocontrol strains into four groups: T. harzianum-T. inhamatum complex, T. longibrachiatum, T. asperellum, and T. atroviride-T. koningii complex. ITS2 sequences were also useful for locating the biocontrol strains inT. atroviride within the complex T. atroviride-T. koningii. None of the biocontrol strains studied corresponded to biotypes Th2 or Th4 of T. harzianum, which cause mushroom green mold. Correlation between different genotypes and potential biocontrol activity was studied under dual culturing of 17 BCAs in the presence of the phytopathogenic fungi Phoma betae,Rosellinia necatrix, Botrytis cinerea, andFusarium oxysporum f. sp. dianthi in three different media.

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