In vitro evaluation of fungicides and bioagents against Fusarium Solani inciting wilt disease of patchouli

Introduction

Patchouli (Pogostemon patchouli Pellet.), also known as Pogostemon cablin Benth., is a member of the mint or Lamiaceae family and is the source of commercial patchouli oil. It appears that the word "patchouli" is derived from the Sanskrit word "Pacholi," which means aromatic herb. Since patchouli oil cannot yet be replaced by a synthetic chemical, it is one of the most significant aromatic crops in the perfume business. Originating in the Philippines, it can be found growing wild in China, India, Malaysia, Indonesia and Singapore. The cultivation of Patchouli is reported to have started first in Java in 1895 with planting material from Singapore, though the identity of the species was uncertain (Ahmed, 2002) [1] . Pogostemon cablin (Blanco) Benth. (patchouli), a pharmacologically significant plant, has been traditionally utilized for the treatment of colds, fevers, headaches, inflammation, digestive disorders, insect and snake bites. Phytochemical investigations have identified key bioactive constituents in patchouli leaves, including patchouli alcohol, β-patchoulene, pogostone, α-bulnesene and β-caryophyllene, which collectively underpin its diverse biological activities. Recent pharmacological studies have validated its antioxidant, antiinflammatory, antimicrobial, antidepressant and anticancer properties. (Mrisho et al., 2025) [5] . The name "Patchouli" has its roots in the Tamil language, derived from the words patchai (or pacchai), meaning 'green,' and ilai, meaning 'leaf.' Together, they evoke the image of "green leaves," aptly describing the plant's lush, vibrant foliage. Across India, the plant is recognized by a rich array of vernacular names such as Pachi in Sanskrit, Pachauli in Hindi, Pachapat in Bengali, Pachila in Malayalam, Pachetene in Kannada, Pacha in Gujarati and Panch in Marathi. These diverse local names underscore its deep cultural integration and longstanding traditional importance in various regions of the country. (Yadav et al., 2017; Magar et al., 2024) [4,10] . Patchouli oil was iso from shade dried leaves of patchouli through hydro distillation employing a Clevenger distillation apparatus, yielding an oil percentage of 3.5%. Physicochemical parameters, including specific gravity, refractive index, optical rotation, acid value and ester value, were subsequently determined to characterize the extracted oil. Quantitative compositional analysis was carried out using Gas Chromatography-Mass Spectrometry (GC-MS), which revealed the presence of several principal constituents, namely alpha-guaiene (9.95%), seychellene (7.14%), alpha-patchoulene (7.08%), alpha-bulnesene (13.16%) and patchouli alcohol (32.54%), with the latter representing the most abundantly occurring compound in the oil fraction. (Yadav et al. 2017) [10] . Patchouli is generally cultivated on dry lands under rain-fed conditions, with fertilization applied according to the specific nutritional requirements of the crop. For optimal growth and yield, the plant requires an annual rainfall ranging between 2,500 and 3,000 mm. (Nasruddin et al. 2015) [6] . Patchouli (Pogostemon patchouli) is vulnerable to various diseases that significantly reduce its planting value. Among those pathogens, Fusarium solani (Mart.) Sacc. stands out as the most predominant fungal pathogen, responsible for considerable yield losses. This pathogen causes wilt in seedlings and, during later stages of plant growth, induces root rot that ultimately results in wilting the affected plants (Pareek and Varma, 2014) [7] . The initial external symptom observed was the of older leaves, which gradually progressed to the middle and younger leaves. The leaves then exhibited a characteristic drying appearance similar to drought stress, despite adequate soil moisture. Brown to black discoloration was noticed on the stem and roots, accompanied by dark brown to reddish discoloration of the vascular tissues. Severe degradation and disintegration of the secondary root surface were also evident. Affected plants showed complete wilting and could be easily uprooted from the soil. Eventually, the entire plant dried up, resulting in premature death (Chavan, 2007) [2] .

Materials and Methods

The present investigation was carried out at the Department of Plant Pathology, College of Agriculture, Dapoli, Dist. Ratnagiri. To evaluate the in vitro efficacy of different fungicides and bioagents against Fusarium solani. The efficacy of fungicides against Fusarium solani was evaluated under in vitro conditions using the poisoned food technique (Sinclair and Dhingra, 1985) [8] . Fungicides belonging to different chemical groups viz., Tebuconazole 25.9% EC, Carbendazim 50% WP, Captan 50% WP, Mancozeb 75% WP, Copper oxychloride 50% WP, Hexaconazole 4% + Zineb 68% WP, Carbendazim 12% + Mancozeb 63% WP, Carboxin 37.5% + Thiram 37.5% WS and Tebuconazole 50% + Trifloxystrobin 25% WG were evaluated. The experiment was conducted in a Completely Randomized Design (CRD) with three replications. Tebuconazole 25.9 % EC 0.1 2.

Copper oxychloride 50 % WP 0.3 6.

Hexaconazole 4% + Zineb 68% WP 0.2 7.

Carbendazim 12% + Mancozeb 63%WP 0.2 8.

Carboxin 37.5 % + Thiram 37.5% WS 0.2 9.

Tebuconazole 50 % + Trifloxystobin 25 % WG 0.1

An in vitro study was conducted to evaluate the antagonistic potential of different biocontrol agents against Fusarium solani using the dual culture technique (Dennis and Webster, 1971) [3] . The bioagents used were four fungal species viz. Trichoderma viride, T. harzianum, T. longibrachiatum and T. koningii, and two bacterial species viz. Pseudomonas fluorescens and Bacillus subtilis.

After seven days of inoculation, observations were recorded on the radial mycelial growth or colony diameter of the pathogen. Per cent mycelial growth inhibition of the pathogen with the fungicides and bioagents over the untreated control was calculated using the formula given by Vincent (1947) [19] . C -T Per cent growth inhibition (I) = × 100 C Where, C = Growth of test fungus in control plate (mm). T = Growth of test fungus in respective treatment plate (mm).

Results and Discussion

In vitro efficacy of fungicides against fusarium solani

The results indicated that all fungicides tested significantly suppressed the growth of Fusarium solani. [2] . evaluated the antagonistic activity of different bioagents against F. solani under in vitro conditions and reported that T. harzianum exhibited the highest inhibition of mycelial growth (78.11%), which was significantly superior to all other bioagents tested. The next most effective bioagent was T. koningii (75.63%), followed by T. viride (74.92%) and T. virens (70.16%). The lowest inhibition was recorded with B. subtilis (57.02%), while Pseudomonas fluorescens showed 65.10 per cent inhibition of mycelial growth.

Acknowledgement

AcknowledgementThe authors sincerely acknowledge the Head, Department of Plant Pathology, Dr. Balasaheb Sawant Konkan Krishi Vidyapeeth, Dapoli, Maharashtra, for providing the necessary facilities and support to carry out this research work.

References

1. Ahmed M. Patchouli an ideal aromatic crop for commercial importance. Guwahati: North Eastern Development Finance Corporation Ltd.; 2002. p. 11.
2. Chavan SS. Studies on fungal diseases of patchouli with special reference to wilt caused by Fusarium solani (Mart.) Sacc. [MSc (Agri) thesis]. Dharwad: University of Agricultural Sciences; 2007. 98 p.
3. Dennis C, Webster J. Antagonistic properties of species-groups of Trichoderma: I. Production of nonvolatile antibiotics. Trans Br Mycol Soc. 1971;57(1):25-39.
4. Magar SS, Shirke GD, Kadam JH, Bodake PS, Kawade SA. Studies on extraction of essential oil from patchouli (Pogostemon cablin). Int J Adv Biochem Res. 2024;8(6):136-141.
5. Mrisho II, Musazade E, Chen H, Zhao H, Xing J, Li X, et al. Unlocking the therapeutic potential of patchouli leaves: a comprehensive review of phytochemical and pharmacological insights. Plants. 2025;14(7):1034.
6. Nasruddin N, Harahap EM, Hanum C, Siregar LAM. Response of three varieties of patchouli (Pogostemon cablin Benth.) to various ranges of drought stress and fertilization. 2015.
7. Pareek V, Varma R. Phytopathological effects and disease transmission in cluster bean seeds grown in Rajasthan. Indian J Plant Sci. 2014;3(2):26-30.
8. Sinclair JB, Dhingra OD. Basic plant pathology methods. Boca Raton (FL): CRC Press; 1985. p. 285315.
9. Vincent JM. Distortion of fungal hyphae in the presence of certain inhibitors. Nature. 1947; 159:850.
10. Yadav RK, Yadav LBP, Rana M. GC-MS analysis of essential oil of Pogostemon cablin Benth. (patchouli oil) of Nepal. J Plant Resour. 2017;15(1):61-65.