In vitro evaluation of fungicides efficacy against Pythium aphanidermatum causing damping off of tomato

Introduction

Tomato is one of the most important warm season vegetables grown all over the world. It belongs to Solanaceae family and is a self -pollinated crop. Tomato is considered as 'protective food' as it is rich in vitamins (A, B1, B2, B6, biotin, folic acid, C, E and K), antioxidants and carbohydrates. Tomato is grown worldwide on an area of 49,17,735 hectares and annual production is estimated around 18,61,07,972.48 tonnes. (FAOSTAT, 2022) [1] . The largest producer of tomato is China followed by India, Turkey, United States and Egypt. In India the tomato covers an area of 8,43,000 hectares and annual production is around 2,06,94,000 tonnes. (FAOSTAT, 2022) [1] . More than 200 pests and diseases are known to attack tomato crop and among them damping off is one of the most important diseases that cause serious losses in nurseries. Damping off causes 25-75% losses per year, depending on the host type and environmental variables (Adhikari et al., 2024) [2] . Damping-off disease caused by Pythium species kills more than 60% of seedlings in the nursery and main field (Manoranjitham et al., 2001) [8] .

Materials and Methods

Isolation of pathogen

Tomato seedlings showing damping off symptoms were collected from field for isolating the pathogen. Diseased collar portion were cut into small bits of 2-3mm size and rinsed in tap water. Bits were then dipped in 0.1% sodium hypochlorite for 30 seconds for surface sterilization. This was followed by rinsing bits three times in sterilized distilled water and then placing them on paper towel to remove excess moisture. These bits were placed on potato dextrose agar medium contained in petri plates. The plates were incubated at 25 ± 2 0 C and checked regularly. The fungal colonies developed around each bit were examined and sub cultured. Based on the morphological and cultural characteristics the fungus was identified as Pythium aphanidermatum. By hyphal tip method the pure culture of P. aphanidermatum was maintained on PDA slants and used for further studies. evaluated at 3 concentrations viz., 0.1%, 0.2% and 0.3%, in vitro by poisoned food technique for their efficacy to inhibit the fungal growth. Potato Dextrose Agar (PDA) medium was used as basal culture medium. 100 ml of PDA was poured in each 250 ml Erlenmeyer flask and then autoclaved. The sterilized PDA media was amended using three concentration (0.1%, 0.2% and 0.3%) of each fungicide. The flasks containing molten poisoned media were shaken well to mix fungicides uniformly. Poisoned PDA from each flask was then poured in sterilized petri plate (15-20 ml / plate), each replicated thrice and allowed to solidify at room temperature. After solidification, a 5 mm disc of about one week old fungus culture was placed at the center of the PDA plates. Poisoned PDA plates were incubated at 25±2 °C for seven days. The petri plates without the poisoned PDA served as control and incubated in same conditions as poisoned PDA plates were incubated. Observation on radial mycelial growth / colony diameter of the P. aphanidermatum was recorded at 3 rd , 5 th and 7 th DAI. Percent of mycelial growth inhibition of the pathogen with the test fungicides on 7 th DAI over the untreated control were calculated (Vincent, 1947) [10] .

Where, C = Growth of the test fungus in untreated control plates. T = Growth of the test fungus in treated plates

Results and discussion

In vitro evaluation of fungicides: In vitro efficacy of the fungicides was evaluated against Pythium aphanidermatum. The efficacy of fungicides was evaluated at 0.1%, 0.2% and 0.3% concentration based on the colony diameter and reduced mycelium growth on PDA. The results presented in Table 1 showed that among the eleven fungicides evaluated, T2 (Tebuconazole 25.9%), T5 (Carbendazim 50%), T12 (Carbendazim 12%+Mancozeb 63%) were most effective as they inhibited the mycelial growth of P. aphanidermatum at all concentrations (0.1, 0.2, 0.3). The next effective treatments that inhibited mycelial growth at 0.2% and 0.3% conc. were T3 (Azoxystrobin 23%) T7 (Thiophanate methyl 70%) and T4 (Propiconazole 13.9% + Difenoconazole 13.9%). Fungicides that completely inhibited the mycelial growth at 0.3% conc. are T8 (Propineb 70%), T9 (Metalaxyl 35%) and T11 (Benalaxyl-M4%+Mancozeb 63%). The least effective fungicide against P. aphanidermatum was found to be T1 (Tetraconazole 3.8%) which showed 49.66%, 61.52% and 65.11% inhibition of mycelial growth at 0.1%, 0.2% and 0.3% respectively. T1 was followed by T5 (Mancozeb 75%) in least effectiveness against P. aphanidermatum which gave 51.11%, 72.72% and 87.57% inhibition at 0.1, 0.2 and 0.3% conc. respectively. The results discussed above are in conformity with the Archana et al. (2020) [3] and Avinash et al., (2018) [4] who reported cent percent inhibition by Tebuconazole 25.9%. Chavan et al. (2017) [6] , Avinash et al. (2018) [4] and Chaithra et al. (2019) [5] reported Carbendazim 50% to give cent percent inhibition of mycelial growth. Carbendazim 12%+Mancozeb 63% was reported to give cent percent inhibition of mycelial growth by Chavan et al. (2017) [6] , Chaithra et al. (2019) [6] and Archana et al. (2020) [3] . [9] who reported Metalaxyl M to show 83.89% and 90.56% inhibition at 0.1% and 0.2% concentration. Jyoti et al. (2019) [7] observed 82.94% average inhibition of mycelial growth by Thiophanate methyl. Chavan et al. (2017) [6] reported Mancozeb to give 64.96%, 70.72% and 76.12% inhibition at 0.15%, 0.2% and 0.3% conc. respectively and Azoxystrobin to give 90.70%, 92.09% and 100% inhibition at 0.05%, 0.1% and 0.2% conc. respectively.

Conclusion

In the research carried it was found that among the eleven fungicides evaluated in vitro against Pythium aphanidermatum Tebuconazole 25.9% W/W, Carbendazim 50% WP and Carbendazim 12%+Mancozeb 63% WP were most effective as they completely inhibited the mycelial growth of P. aphanidermatum at all concentrations (0.1%, 0.2%, 0.3%). The least effective was found to be Tetraconazole 3.8% W/W (49.66%, 61.52%, 65.11) and Mancozeb 75% WP (51.11%, 72.72%, 87.57%) at (0.1%, 0.2%, 0.3%) respectively.

References

1. Adhikari A, Oli D, Poudel P, Magar PB, Pandit S, Pokhrel A, et al. Pythium-induced damping-off disease and its management in tomato (Solanum lycopersicum L.): A review. Agricultural Science & Technology. 2024;16(1):1313-8820.
2. Archana TS, Mesta RK, Basavaraj N, Hegde NK, Basavarajappa MP, Kiran Kumar KC, et al. Evaluations of effective molecules against the pathogen complex causing rhizome rot of ginger. International Journal of Chemical Studies. 2020;8(5):2334-2340.
3. Avinash, Bijendra K, Shivani. In vitro and glass house evaluation of fungicides against the pathogens associated with rhizome rot complex of ginger in Kumaon region of Uttarakhand. International Journal of Chemical Studies. 2018;6(5):1364-1372.
4. Chaithra J, Kulkarni S, Sunkad G, Amresh YS, Patil S. In-vitro efficacy of fungicides and bioagents for the management of soft rot of ginger caused by Pythium aphanidermatum. International Journal of Current Microbiology and Applied Sciences. 2019;8(9):23197706.
5. Chavan PG, Apet KT, Borade RS. Efficacy of fungicides and bioagents against Pythium aphanidermatum causing rhizome rot of turmeric. International Journal of Current Microbiology and Applied Sciences. 2017;6(11):4312-4320.
6. Jadhavar JB, Magar SJ, Bhosale AR, Khillare PR, Rothe AS. Efficacy of fungicides against Pythium aphanidermatum causing damping-off of tomato seedling. International Journal of Chemical Studies. 2019;7(5):1055-1057.
7. Manoranjitham SK, Prakasam V, Rajappan K. Biocontrol of damping off of tomato caused by Pythium aphanidermatum. Indian Phytopathology. 2001;54:5961.
8. Prasanna MR, Kalariya Kuldeepsingh A, Saran Parmeshwar L, Roy S. Efficacy of fungicides and biocontrol agents against Pythium aphanidermatum causing damping-off disease in ashwagandha (Withania somnifera L. Dunal). Medicinal Plants -International Journal of Phytomedicines and Related Industries. 2019;11(4):404-409.
9. Vincent JM. Distortion of fungal hyphae in presence of certain inhibitors. Nature. 1947;150:850.