In-vitro evaluation of plant extracts and cow urine against Colletotrichum capsici f. sp. cyamopsicola causing anthracnose of cluster bean

Introduction

Cluster bean (Cyamopsis tetragonoloba (L.) Taub.), commonly known as guar, is an important leguminous crop valued for its tender pods, fodder and seed and is also an important source of guar gum. The crop is cultivated under diverse agro-climatic conditions and has considerable agricultural and industrial importance. However, its production is affected by several diseases, among which anthracnose is an important constraint. Colletotrichum species are important plant pathogenic fungi responsible for anthracnose diseases in numerous crops. In cluster bean, anthracnose is associated with Colletotrichum capsici f. sp. cyamopsicola. The disease affects different plant parts and may result in necrotic lesions, premature drying and deterioration of crop quality. Warm and humid environmental conditions favour the development and spread of anthracnose, making effective disease management particularly important. Management of fungal diseases has traditionally depended largely on chemical fungicides. However, their repeated and indiscriminate use may lead to concerns related to fungicide residues, environmental contamination and adverse effects on non-target organisms. Therefore, increasing attention is being given to plant-derived products and locally available organic inputs as potential components of eco-friendly disease management programmes. Plant extracts contain several biologically active compounds possessing potential antifungal properties. Earlier investigations have demonstrated the inhibitory activity of different botanical extracts against Colletotrichum species. Gurav et al. (2013) [3] reported considerable inhibition of C. gloeosporioides by soapnut and eucalyptus extracts. Jagtap et al. (2014) [4] also reported inhibitory activity of different aqueous botanical extracts against C. truncatum. Bhardwaj et al. (2015) [5] observed strong antifungal activity of Sapindus mukorossi extracts against C. lindemuthianum. Similarly, cow urine has been reported to possess antifungal activity against plant pathogenic fungi. Kambar et al. (2013) [7] studied the inhibitory effect of cow urine against C. capsici isolated from chilli anthracnose and reported variation in inhibition with concentration. Kekuda et al. (2014) [8] also evaluated cow urine extracts against C. capsici and reported their antifungal potential. Despite these reports, comparatively limited information is available on the efficacy of locally available plant extracts and cow urine against C. capsici f. sp. cyamopsicola associated with anthracnose of cluster bean. Therefore, the present investigation was undertaken to evaluate selected plant extracts and different concentrations of cow urine against the pathogen under in-vitro conditions.

Materials and Methods

Experimental site and pathogen

The investigation was conducted during 2025-2026 at the Department of Plant Pathology, College of Agriculture, Dr. Balasaheb Sawant Konkan Krishi Vidyapeeth, Dapoli, District Ratnagiri, Maharashtra. Anthracnose infected cluster bean samples were collected and the pathogen was isolated on Potato Dextrose Agar (PDA). The pathogen was purified and maintained on PDA. Pathogenicity was confirmed on healthy cluster bean plants, and the pathogen was identified as Colletotrichum capsici f. sp. cyamopsicola based on its cultural and morphological characteristics.

In-vitro evaluation of plant extracts

Five plant extracts, viz., Ghaneri (Lantana camara), Nilgiri (Eucalyptus globulus), Dhatura (Datura stramonium), Karanj (Pongamia pinnata) and Soapnut (Sapindus trifoliatus), were evaluated at 10 per cent concentration. The poisoned food technique described by Nene and Thapliyal (1993) [9] was followed for evaluating the antifungal activity of the plant extracts. The experiment was conducted under Completely Randomized Design (CRD). The required quantity of each plant extract was incorporated into molten PDA to obtain the desired concentration. The amended medium was poured into sterilized Petri plates. A mycelial disc obtained from the actively growing margin of the pathogen culture was placed at the centre of each plate. Plates containing unamended PDA served as the untreated control. The inoculated plates were incubated at 27 ±2°C.

Mycelial growth was recorded after seven days of incubation.

In-vitro evaluation of cow urine

Cow urine obtained from Konkan Kapila and Jersey breeds was evaluated at 10, 20, 30, 40 and 50 per cent concentrations against C. capsici f. sp. cyamopsicola. The poisoned food technique was followed. The required quantity of cow urine was incorporated into molten PDA to obtain the respective concentrations. The amended medium was poured into sterilized Petri plates and inoculated with a mycelial disc of the pathogen. Unamended PDA served as the control. The plates were incubated at 27 ±2°C and colony growth was recorded after seven days.

Assessment of mycelial growth inhibition

The mean colony diameter was recorded for each treatment. The percentage inhibition of mycelial growth over the untreated control was calculated using the formula proposed by Vincent (1947) [10] :

C -T Per cent Growth Inhibition (I) = C

Where: I = Per cent inhibition of mycelial growth C = Colony diameter in untreated control T = Colony diameter in treatment

Results and Discussion

In-vitro efficacy of plant extracts against

The results revealed that all the plant extracts tested inhibited the mycelial growth of C. capsici f. sp. cyamopsicola compared with the untreated control. [3] reported considerable inhibition of C. gloeosporioides by soapnut extract at 10 per cent concentration. Similarly, Bhardwaj et al. (2015) [5] reported strong antifungal activity of Sapindus mukorossi fruit extract against C. lindemuthianum. Vibhute et al. (2024) [11] also reported soapnut rind extract as the most effective among the organic plant extracts evaluated against C. gloeosporioides. These findings support the potential of Sapindus extracts against different Colletotrichum species. Jagtap et al. (2014) [4] reported inhibitory effects of aqueous botanical extracts, including eucalyptus, against C. truncatum. The differences in efficacy among the botanicals may be associated with variations in their active constituents, extraction procedures, concentration and susceptibility of the pathogen.

In-vitro efficacy of cow urine concentrations

The results showed that cow urine obtained from both Konkan Kapila and Jersey breeds inhibited the mycelial growth of C. capsici f. sp. cyamopsicola. In Konkan Kapila cow urine, the mean colony diameter decreased from 78.00 mm at 10 per cent concentration to 25.25 mm at 50 per cent concentration. Correspondingly, inhibition increased from 13.33 per cent to 71.94 per cent. In Jersey cow urine, the colony diameter decreased from 78.37 mm at 10 per cent to 32.25 mm at 50 per cent concentration, while inhibition increased from 12.91 per cent to 64.16 per cent. Thus, the 50 per cent concentration was the most effective for both breeds. At 50 per cent concentration, Konkan Kapila cow urine showed greater inhibition than Jersey cow urine. The present findings are in agreement with earlier reports on the antifungal activity of cow urine. Kambar et al. (2013) [7] reported inhibitory activity of cow urine against C. capsici isolated from chilli anthracnose and observed differences in inhibition at different concentrations. Kekuda et al. (2014) [8] also reported antifungal activity of cow urine extracts against C. capsici. Similarly, studies cited in the thesis have demonstrated the potential of cow urine as an organic antifungal input.

Conclusion

The obtained result indicated that among the plant extracts evaluated at 10 per cent concentration, Soapnut (Sapindus trifoliatus) was the most effective, recording 52.22 per cent inhibition, followed by Nilgiri (Eucalyptus globulus) with 42.63 per cent inhibition. Among the cow urine treatments, Konkan Kapila cow urine at 50 per cent concentration recorded the highest inhibition of 71.94 per cent, followed by Jersey cow urine at 50 per cent concentration, which recorded 64.16 per cent inhibition.

Acknowledgement

AcknowledgmentsThe authors gratefully acknowledge the Department of Plant Pathology, College of Agriculture, Dr. Balasaheb Sawant Konkan Krishi Vidyapeeth, Dapoli, for providing the laboratory facilities and necessary support for conducting the present investigation.

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