In vitro efficacy of fungicides against Fusarium oxysporium f.sp. cubense

Introduction

Since many diseases infested the banana cultivation, but the most destructive disease of banana plantain is Fusarium oxysporum f.sp. cubense. Fusarium oxysporum f.sp. cubense is also known as Panama wilt disease. Panama wilt is soil borne disease, fungus colonizes the roots of rhizomes and pseudostem with characteristic symptoms of wilting before plant eventually dies (Wardlaw, 1961; Stover, 1962) [9,6] . Panama wilt is most destructive diseasecausing heavy losses in banana growing areas. Panama wilt is considered to be originated in Southeast Asia from there was disseminated rapidly throughout the world with infected rhizomes (Stover, 1962) [6] . Panama wilt is major threat in the world for banana cultivation, infected rhizomes and susceptible cultivars play significant role in spread of this disease. Panama wilt of banana is effectively controlled by applying disease-preventive practices such as planting disease-free propagating material. Once infested with the pathogen, the only way of continuing banana production is by means of planting cultivars with resistance to the disease (Deacon, 1984; Ploetz and Pegg, 2000; Viljoen, 2002; Ploetz et al., 2003) [1,4,7,5] . Cultivar with resistance to Foc have been identified, but this cultivar are not acceptable in local market by farmers (Viljoen, 2002) [7] . In vitro evaluation of fungicides provides preliminary information regarding its efficacy against a pathogen within a shortest period of time and therefore, serves as a guide for further field testing. Hence, the present investigation was undertaken to screen a range of fungicides, including new chemical formulations, for their ability to inhibit the mycelial growth of Foc in vitro.

Material and Methods

An experiment was conducted during 2023 at College of Agriculture, Dhule (Maharashtra) to find out the effective fungicide against Fusarium oxysporum f.sp. cubense in in vitro. The experiment was designed in Complete Randomized Design (CRD) with four replications and six treatments. The six fungicides were evaluated against Panama wilt pathogens under laboratory conditions by following poison food technique (Nene and Thapliyal, 1993) [2] . The details of the fungicides used were given below table 1. The fungicides suspension was made by adding required quantity of fungicides to the melted PDA medium to obtain the desired concentration. 20 ml of poisoned medium was poured in each sterilized Petri plates. Mycelial disc of 5 mm size from actively growing zone of seven days old culture was cut by a sterile cork borer and one such disc was placed at the centre of each agar plate. Control treatment was maintained without adding any fungicide to the medium. Four replications were maintained for each concentration. Then such plates were incubated at room temperature and radial growth was measured when fungus attained maximum growth in control plates. percent inhibition of mycelial growth over control was calculated by using the formula given by Vincent (1947) [8] .

C-T PI = X 100 C

Where, PI = percent inhibition. C = Radial growth of test fungus in control plate T = Radial growth of test fungus in treated plate

Results and Discussion

The efficacy of various fungicidal treatments against Fusarium oxysporum f.sp. cubense was evaluated in vitro based on the radial mycelial growth inhibition. The results clearly revealed that significant variation in the degree of fungal suppression depending on the chemical used. The highest inhibition (100%) of fungal growth was recorded in the treatments Propiconazole 25% EC @ 0.5 ml/L, Carbendazim 50% WP @ 1 g/L and Carbendazim 12% + Mancozeb 63% WP @ 2.5 g/L all of which completely suppressed the radial growth of the fungus, with a mean colony diameter of 0.00 mm. Treatment Tebuconazole 25.9% EC also showed very high efficacy with 99.14% inhibition and a minimal colony diameter of 0.50 mm. Moderate inhibition was recorded with Copper Oxychloride 50% WP @ 2.5 g/L and Azoxystrobin 11% + Tebuconazole 18.3% SC @ 1 ml/L, which resulted in mean colony diameters of 22.31 mm and 29.63 mm, corresponding to 75.21% and 67.07% inhibition over control, respectively (Table 2). The untreated control showed maximum fungal growth with a colony diameter of 90.00 mm, confirming the virulence of the pathogen in the absence of any fungicidal interference (Figure 1). Overall, the study suggests that Propiconazole, Carbendazim, and Carbendazim + Mancozeb are the most promising fungicides for managing F. oxysporum f. sp. cubense under in vitro conditions, and their field evaluation under natural conditions would be necessary to confirm their practical utility in disease management programs. Similar study was carried out by Niwas et al., (2020) [3] which found that among the three fungicides tested, (carbendazim, azoxystrobin and propiconazole), carbendazim @ 500 ppm and 750 ppm completely inhibited the growth of Fusarium oxysporum f. sp. cubense followed by azoxystrobin (32.96, 11.30, 8.12 and 7.16 mm in 100, 250, 500 and 750 ppm, respectively). The maximum mycelial growth was recorded in propiconazole, the similar result, it shows strong support to current finding.

Conclusion

In this experimentation, among six different fungicides evaluated against FOC TR1, complete inhibition over control was observed in propiconazole, carbendazim and carbendazim + Mancozeb, respectively. While the tebuconazole, copper oxychloride and azoxystrobin + tebuconazole show moderate inhibition over control.

References

1. Deacon JW. Panama disease of banana in South Africa. Horticultural Science. 1984;1:29-31.
2. Nene YL, Thapliyal PN. Poison food technique. Fungicides in Plant Disease Control. 1993;2:413-415.
3. Niwas R, Chand G, Azad CS. in vitro evaluation of fungicides against growth of Fusarium oxysporum f. sp. cubense causing Panama wilt disease of banana. Int J Chem Stud. 2020;8(1):191-194.
4. Ploetz RC, Pegg KG. Fungal diseases of root, corm and pseudostem. In: Jones DR, editor. Disease of banana, Abaca and Enset. Wallingford: CAB International; 2000. p. 143-172.
5. Ploetz RC, Thomas JE, Slabaugh WR. Diseases of banana and plantain. In: Ploetz RC, editor. Disease of tropical fruit crops. Wallingford: CAB International; 2003. p. 109-112.
6. Stover RH. Fusarial wilt (Panama disease) of bananas and other Musa species. Kew, Surrey, UK: Commonwealth Mycological Institute; 1962.
7. Viljoen A. The status of Fusarium wilt (Panama disease) of banana in South Africa. S Afr J Sci. 2002;98(7/8):341-344.
8. Vincent JM. Distortion of fungi hyphae in the presence of certain inhibitors. Nature. 1947;159:850.
9. Wardlaw CW. Banana diseases, including plantains and Abaca. London: Longmans, Green and Co. Ltd.; 1961.