S. Sriram ¹, M. J. Savitha ¹, B. Ramanujam ¹

Affiliations
1 National Bureau of Agriculturally Important Insects, H. A. Farm Post, Hebbal, Bellary Road, Hebbal, Bangalore, 560 024, Karnataka, IN

Abstract

Coconut coir dust, commercially available as coco-peat, is used in raising the seedlings of vegetable crops in tropical countries. Coir-pith and other derivates of coconut husk have been well recognized as substrates for the multiplication of Trichoderma spp. and commercial nurseries use coco-peat for raising the seedlings. In the present study, coco-peat enriched with Trichoderma harzianum was used for raising tomato and chilli seedlings to test the effect of the same on managing wilt caused by Fusarium oxysporum f. sp. lycopersici in tomato and damping off and ischolar_main rot caused by Phytophthora capsici in chillies in nurseries. The enrichment with T. harzianum, resulted in reduced wilt incidence (5-7.5%) compared to control (38.75%) in tomato with increased plant growth parameters. Though germination was reduced compared to control (without pathogen), there was reduction in P. capsici infection in chillies by up to 50% compared to coco-peat without Trichoderma enrichment. The use of coco-peat enriched with T. harzianum can be adopted by commercial nurseries for better plant growth and reduced incidence of tomato wilt and chilli ischolar_main rot while raising disease free and healthy seedlings.

Keywords

Trichoderma spp., Coco-Peat, Fusarium oxysproum f. sp. lycopersici, Phytophthora capsici, Tomato, Chilli, Commercial Nurseries.

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S. Sriram ¹, M. J. Savitha ¹

Affiliations
1 National Bureau of Agriculturally Important Insects, Post Bag No. 249, H. A. Farm Post, Hebbal, Bellary Road, Bangalore 560 024, Karnataka, IN

Abstract

Traditionally serial dilution method is used for the enumeration of viable propagules in a microbial formulation. Conidia of some fungal agents like Trichoderma spp. are hydrophobic in nature. They repel water and are not dispersed uniformly in water. To enhance uniform distribution, dispersing agents like Tween 20 have to be used. In many articles in the published literature, high CFUs (>10¹¹ CFUs g^-1) have been either been claimed or reported to be present in formulations. Further considering the volume (4/3 × 3.14 × r³) occupied by each conidium (minimum 2 micron diameter), realistically we cannot expect high Colony Forming Units (CFUs) reported or claimed in many research papers. In the present report an attempt was made to estimate the possible 'number of conidia per cc' and 'number of conidia per g' of Trichoderma harzianum spores (NBAII Th10-MTCC 5584). The results showed that even at higher dilutions (>10^-18 to 10^-20) colonies of Trichoderma appeared on plates which is not theoretically possible. It is proposed that while enumerating the viable propagules in a formulation the serial dilution has to be done with Tween 20 and the tips should be changed for each dilution without fail. The dilution should be restricted to 10⁹ or 10¹⁰. The limitations of the serial dilution beyond 10¹⁰ and precautions to be taken are discussed.

Keywords

Trichoderma spp., Formulation, Serial Dilution, Enumeration, Viability.

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S. Sriram ¹, S. B. Manasa ², M. J. Savitha ¹

Affiliations
1 National Bureau of Agriculturally Important Insects, Post Bag No. 2491, H. A. Farm Post, Bangalore 560024, Karnataka, IN
2 Department of Plant Science, School of Life Sciences, Bharathidasan University, Tiruchirapalli 620024, Tamil Nadu, IN

Abstract

Eleven isolates of Trichoderma harzianum were screened for their potential to induce systemic resistance against Phytophthora capsici in red pepper plants. The effect of talc formulations of these eleven isolates on induction of glucanase activity and phenol content was studied. There was a significant increase in glucanase activity in plants treated with Th8 and Th1 (94 and 90 μg glucose released min^-1 g^-1) compared to control (77 μg). Similarly phenol content also increased in plants treated with Th4, Th7 and Th10 (48-59 μg g-1) compared to control (34 μg g^-1). Cell wall glucan elicitors were extracted from T. harzianum isolate Th10 that had been reported earlier as an efficient biocontrol agent. Treatment with elicitor preparations also induced high glucanase activity (40 μg glucose released min-1 g-1) and increased phenol content (42 μg g^-1) compared to control where the glucanase activity was 33 μg glucose released min^-1 g^-1 while phenol content was 27 μg g^-1. Similarly the elicitor treatment as seedling dip reduced P. capsici infection to 23% compared to control (93%). The potential use of ISR eliciting isolates in the biocontrol of P. capsici in red pepper is discussed.

Keywords

Cell Wall Glucan Elicitor, Induced Systemic Resistance (ISR), Phytophthora capsici, Red Pepper, Trichoderma harzianum.

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Suresh Patil ¹, S. Sriram ¹, M. J. Savitha ¹

Affiliations
1 National Bureau of Agriculturally Important Insects, Post Bag No, 2491, H.a. Farm Post, Bellary Road, Hebbal, Bangalore 560024, Karnataka, IN

Abstract

Fusarium spp. isolated from rhizosphere soils of tomato from Karnataka, Tamil Nadu and Gujarat states of India were tested for their pathogenicity. Among these isolates, six were found non-pathogenic to tomato, red gram, bengal gram, groundnut, red pepper, water melon, castor and banana. These non-pathogenic isolates protected tomato plants when co-inoculated with pathogen isolate under pot culture conditions. Treatment with non-pathogenic Fusarium isolates improved the plant growth parameters (length and weight of ischolar_main and shoot). These non-pathogenic Fusarium isolates can be exploited for the biocontrol of wilt disease.

Keywords

Biocontrol, Non-pathogenic Isolates, Fusarium Spp., Tomato, Wilt.

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