M. Ranganathaswamy ¹, A. K. Patibanda ¹, G. Nageshwara Rao ¹

Affiliations
1 Department of Plant Pathology, Agricultural College, Bapatla 522 101, Andhra Pradesh, IN

Abstract

Thirty nine agrochemicals comprising eighteen fungicides, eleven insecticides, six fertilizers and four herbicides were evaluated at different concentrations against two isolates of Trichoderma spp., and EC₅₀ and EC₉₀ values were calculated based on inhibition in radial growth. Isolate T. virens TV9, obtained from citrus orchard-relatively less exposed to agrochemicals was found more sensitive compared to isolate T. harzianum Th4, obtained from cotton ecosystem relatively more exposed to agrochemicals. Among fungicides, benzimidazoles showed higher toxicity followed by chlorothalonil and triazoles when mean EC₅₀ values were compared. Wettable sulphur, Bordeaux mixture, azoxystrobin and mancozeb were found to be less toxic to Trichoderma spp. Among insecticides, organophosphorous group was found more toxic while carbofuran followed by spinosad were least toxic. Among fertilizers Zinc sulphate and diammonium phosphate were found highly toxic whereas potassium nitrate, muriate of potash and ammonium sulphate showed less toxicity. All the four test herbicides, i.e., pendimethalin, alachlor, glyphosate and 2, 4-D were found to be toxic to Trichoderma spp.

Keywords

Toxicity, Trichoderma spp., Fungicides, Insecticides, Fertilizers,Herbicides, EC₅₀ and EC₉₀.

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A. K. Patibanda ¹, B. Sen ¹

Affiliations
1 Division of Plant Pathology, Indian Agricultural Research Institute (ICAR), Pusa, New Delhi, 110012, IN

Abstract

In vitro interactions of antagonist Aspergillus niger isolate AN 27 and muskmelon wilt pathogen Fusarium oxysporum f. sp. melonis isolate MM 37 revealed three distinct growth phases of A. niger AN 27-initial normal growth with black colony colour due to sporulation, suppressed growth and sporulation followed by revived growth and sporulation. Change in medium pigmentation from violet to pink and formation of abundant thick mycelial strands and chains of chlamydospores were observed in F. oxysporum f. sp. melonis MM 37. Change in medium pigmentation of MM 37 was attributed to the change in medium pH brought by AN 27 by constitutively producing organic acids. Mechanisms involved in AN 27 antibiosis were production of organic acids, antimicrobial substances (n-butanol extract) and extra cellular enzymes - all of which inhibited microconidial germination of MM 37. Seed coating with A. niger AN 27 spores or seedling dip in its spore suspension protected muskmelon seedlings from Fusarial wilt in Rapid Pathogenicity test.

Keywords

Aspergillus niger, Biological Control, Fusarium oxysporum f. sp. melonis, Muskmelon Wilt.

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A. K. Patibanda ¹, B. Sen ²

Affiliations
1 Agricultural Research Station, Tandur 501 141, Ranga Reddy District, Andhra Pradesh, IN
2 Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi 110012, IN

Abstract

Seven isolates of the antagonist Aspergillus niger van Teigh and three isolates of the muskmelon wilt pathogen Fusarium oxysporllm f. sp. melones were assayed for their in vitro interactions. The most virulent isolate of the pathogen was highly sensitive to antagonism compared to less virulent isolate. Variation existed among different A. niger isolates in their antagonistic potential. Observations on overgrowing ability of the antagonist, A. niger werc more useful in screening isolates compared to other parameters such as inhibition zone, radial growth of the test pathogen and I or of the test antagonist in A. niger Vs F. oxysporum r. sp. melonis system. Isolate AN 27 was found promising based on its biocontrol capabilities.

Keywords

Antagonism, Aspergillus niger, Fusarium oxysporum f. sp. melonis, Muskmelon, Wilt.

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A. K. Patibanda ¹, R. D. Prasad ²

Affiliations
1 Acharya N. G. Ranga Agricultural University, Agricultural Research Station, Tandur 501 141, Ranga Reddy District, Andhra Pradesh, IN
2 Directorate of Oilseeds Research, Rajendranagar, Hyderabad 500 030, IN

Abstract

Four Triehodenna isolates were tested for in vitro their antagonistic potential against safflower wilt causing pathogens Fusarium oxysporllnl f. sp. earthami and Macrophomina phaseolilla. Trichoderma viride (PDBC TV 32) and T. harzianum (POne TH 10) were effective against both the pathogens. Trichoderma viride, isolated from the Fllsarium wilt sick plot in Tandur was effective only against M. phaseolin a, while F. oxysporllm f. sp. earlhami had inhihitory effect on sporulation of T. viride.

Keywords

Antagonism, Fusarium oxysporuni f. sp. cartlwmi, Macrophomina phuseolilla, Trichodermaspp.

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A. K. Patibanda ¹, J. P. Upadhyay ², A. N. Mukhopadhya ³

Affiliations
1 Agricultural Research Station, Tandur 501 141, Ranga Reddy District, Andhra Pradesh, IN
2 Department of Plant Pathology, Tirhut College of Agriculture, Dholi, Rajendra Agricultural University, Muzaffarpur 843 121, Bihar, IN
3 151, Akansha, Udyan-II, Raibarcilly Road, Lucknow 226025, U. P., IN

Abstract

Trichoderma harzianum Rifai application either to soil as wheat bran saw dust (WBSD) preparation or on the groundnut seeds as spore coat proved effective against selerotium wilt caused by Sclerotium rolfsii Sacc. Synergistic and positive effects on disease control were registered when T. harzianum-WBSD preparation was applied to soil in integration with Vitavax or Vitavax-200. Integration of Thiram (seed coating) and soil application of antagonist was found compatible and synergistic. However, seed treatment with both antagonist and Thiram was found incompatible and hence may not be practically feasible for disease reduction.

Keywords

Biocontrol, Fungicides, Groundnut, Integration, Sclerotium rolfsii, Trichoderma harzianum.

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