Groundnut germplasm exchange has played a significant role in crop improvement programmes by providing wide genetic diversity world over. However, there is an inherent risk of introduction of new exotic pathogens or new/more virulent races of a pathogen into new areas. The basic principle of plant quarantine is to regulate the movement of seed material to mitigate the associated pest risk. Salvaging, a process of disinfecting infected seed, is an important quarantine strategy to prevent the introduction of new pathogens or virulent races into new areas.

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Nov 2019
Evaluation of fungicides for their efficacy against
seed-borne fungi of Groundnut (Arachis hypogaea)
BD Devamani, P Humayun and Rajan Sharma
Plant Quarantine Unit, Research Program - Asia, International Crops Research Institute for the Semi-Arid Tropics,
Patancheru-502324, Telangana, India
Table 1. Details of fungicides tested.
Fungicides Trade name Dosage(g/kg of seeds
Carbendazim 50% WP Bavistin 3
Mancozeb 75%WP Dithane M - 45 3
Carbendazim 12%+ Mancozeb 63%WP Saaf 3
Thiram 75 WP Thiram 3
Carbendazim +Thiram 1:1 ratio 3
Tebuconazole 50%+Trifloxystrobin 25%WG Nativo 0.5
Captan 50% WP Captaf 3
Captan 70%+ Hexaconazole 5% WP Taqat 2
Tricyclazole 75% WP Beam 2
Tebuconazole 2% DS Raxil 1.5
Metalaxyl 35% WS Metal 2
Metalaxyl 4%+ Mancozeb 64% WP Ridomilgold 2
Tridemefon 25% WP Bayleton 2
Chlorothalonil 75%WP Kavach 2
Myclobutanil 10% WP Index 2
Dimethomorph 50% WP Acrobat 2
Thiophanate methyl 70% WP Roko 2
Fig. 2. Seed germination in treated and untreated groundnut seed.
Introduction
Groundnut germplasm exchange has played a significant role in crop improvement programmes by
providing wide genetic diversity world over. However, there is an inherent risk of introduction of new exotic
pathogens or new/more virulent races of a pathogen into new areas.
The basic principle of plant quarantine is to regulate the movement of seed material to mitigate the
associated pest risk. Salvaging, a process of disinfecting infected seed, is an important quarantine strategy
to prevent the introduction of new pathogens or virulent races into new areas.
Groundnut seed is known to be infected by a large number of seed-borne fungal pathogens that
necessitates the identification of effective fungicides for seed treatment. Therefore, an effort was made
to evaluate the efficacy of different fungicides against seed-borne fungi of groundnut to select the best
fungicide for seed treatment.
Material and Methods
The Infected seeds were treated with fungicides to eradicate seed borne fungi (Table 1). Seeds treated with
different fungicides were assayed for seed borne fungi by employing standard blotter method; untreated
seeds served as a control. The Petri plates containing treated and untreated seeds were incubated at 22
±2 °C under near ultra violet (NUV) light with 12h alternate cycles of light and dark for seven days. After
incubation, seeds were examined for the presence of fungi under stereo-binocular microscope. The fungi
were identified based on the morphological characters (Ellis, 1971; Barnett, 1972; Ahmed KM and Ravinder
Reddy Ch 1993) and data were expressed as percent infected seed.
Results and discussion
▪▪ Seven fungi, Aspergillus niger (89%), Aspergillus flavus (17%), Aspergillus spp. (9.5%), Penicillium
notatum (7.5%), Rhizopus sp. (35.5%), Rhizoctonia bataticola (11.5%) and Fusarium sp. (4%) were
detected in the infected groundnut seeds in control plates (Fig 2 & 3).
▪▪ Seed treatment with Saaf @ 3 g/kg seed significantly reduced (96%) seed borne fungi over control
(Fig 1).
▪▪ The presently recommended fungicide, carbendazim + thiram (1:1) @ 3 g/kg seed, being used for
salvaging the infected groundnut seeds recorded 94 percent reduction over control followed by Nativo
@ 0.5 g/kg seed (92%).
▪▪ In addition to reduction in seed borne fungal infection, there was increase in seed germination as well
(Fig. 2).
Treated Untreated
Conclusion
Seed treatment with Saaf (Carbendazim 12% + Mancozeb 63%WP) @ 3 g/kg seed could be recommended
to eliminate the seed borne fungal infection in groundnut for the safe exchange of seed material as well as
cleaning of groundnut seed for regeneration for conservation.
References
Ahmed KM and Ravinder Reddy Ch. 1993. A pictorial guide to the identification of seedborne fungi of
sorghum, pearl millet, finger millet, chickpea, and groundnut. Information Bulletin no.34. Patancheru. AP
502324, India: International Crops Research Institute for the Semi-Arid Tropics 200pp. ISBN 92-9066-251-4.
Burnett HL. 1972. Illustrated genera of Imperfect Fungi. Burges Pub Com., Minnesota, 213 pp.
Ellis MB. 1971. Dematiaceous hyphomycetes. Kew, Surrey, England: Commonwealth Mycological Institute.
608 pp.Fig. 1. Percent reduction of fungal infection by different fungicides.
Fig.3. Photomicrographs of groundnut seed borne fungi.
Percentreductionoffungal
infectionovercontrol
Fungicides
Growth and sporulation of Aspergillus niger on seed
Growth and sporulation of Penicillium notatum on seed
Sclerotia of Rhizoctonia bataticola on seed
Growth and sporulation of Rhizopus sp. on seed
Growth and sporulation of Fusarium sp. on seed
Growth and sporulation of Aspergillus flavus on seed
Conidia and conidiophore of Penicillium notatum
Conidia of Macrophomina phaseolina
Sporangiophore and sporangiospores of Rhizopus sp.
Conidia and conidiophore of Aspergillus niger
Growth and sporulation of Aspergillus spp. on seed
Micro and macro conidia of Fusarium sp.