To evaluate in vitro efficacy of different fungicides against Pyricularia grisea (Cooke) Sacc. Causing Blast of Pearl Millet [Pennisetum glaucum (L.) R. BR]

Introduction

Pearl millet [Pennisetum glaucum (L.) R. Br.] is an extremely cross-pollinated diploid (2n =2x = 14) with vast genome size (∼2352 Mbp) monocot belonging to the family Poaceae. It is believed to be originated from Dhar Tichitt, a Saharan site in Mauritania of West Africa around 3500 B.C. (Amblard and Pernes, 1989) [1] . India is the greatest creator of pearl millet on the planet having a zone of 7.4 million ha and making of 9.13 million tons with productivity of 1237 kg/ha. Pearl millet blast is a destructive fungal disease caused by the pathogen Pyricularia grisea. This disease has the potential to cause significant yield losses, compromising food security in regions where pearl millet is a dietary staple. The pathogen infects the plant's leaves, stem, and grain, leading to reduced grain quality and quantity. Farmers who rely on pearl millet as a vital source of nutrition and income are particularly vulnerable to the economic repercussions of pearl millet blast. Efficacy of nine systemic fungicides viz Carbendazim 50 WP, Propioconazole25 EC, Hexaconazole 5 EC, Difenoconazole 25EC, Tridemorph 80EC, Tebuconazole 25EC, Thiophanate Methyl 70WP, Benomyl 50WP and Kasugamycin 3SL were determined at 500ppm and 1000 ppm concentrations against Pyricularia grisea following Poisoned Food Technique (Schimitz, 1930) [7] in vitro. All the tested fungicides significantly inhibited the mycelial growth at these concentrations. PDA medium amended with test concentrations of the fungicides.

Materials and Methods

The bio-efficacy of nine fungicides viz., Carbendazim 50WP, Propioconazole 25 EC, Hexaconazole 5 EC, Difenoconazole 25 EC, Tridemorph 80 EC, Tebuconazole 25 EC, Thiophanate-methyl 70 WP, Benomyl 50WP and Kasugamycin 3SL was evaluated under In vitro conditions using Poisoned Food Technique (Schimitz, 1930) [7] against P. grisea to record the inhibition of radial growth using PDA medium. The fungicides were evaluated at 500 and 1000 ppm concentration. The requisite quantities of fungicides were incorporated aseptically to PDA medium cooled to 45 ºC, so as to, give the required concentrations. 20 ml of the poisoned PDA medium was poured into each flat-bottomed sterile Petri dish. The Petri plates were then inoculated by cutting 5.0 mm of 10 days old mycelial discs of Pyricularia grisea with a sterile cork borer and incubated at 28±1 ºC. The inoculated Petri plates were wrapped with cellophane film to minimize the chances of contamination. Three replications were maintained for each treatment. The experiment was conducted in completely randomized design (CRD). The fungus growth on the PDA medium without any fungicide served as control. The radial growth (mm) of the colony was recorded when maximum growth (14 days) in control plates was noticed. The petri plates were then incubated in an incubator at 28 ± 2 0 C. The diameter of the colony was measured after seven days of incubation. The colony diameter of treated plates was compared with control taken as measure of toxicity.

Details of Experiment

The growth of fungal colony by excluding five mm fungal inoculum disc from measured diameter of colony. The percent inhibition was calculated by the following formula given by Vincent (1947) [8] .

R = {(C -T) / C} × 100

Where, R = Percent inhibition, C = Radial growth of pathogen colony in control T = Radial growth of pathogen colony in treatment

Results and Discussion

In-vitro evaluation of various fungicides against Pyricularia grisea: Efficacy of nine systemic fungicides viz Carbendazim 50 WP, Propioconazole 25 EC, Hexaconazole 5 EC, Difenoconazole 25EC, Tridemorph 80EC, Tebuconazole 25EC, Thiophanate Methyl 70WP, Benomyl 50WP and Kasugamycin 3SL were determined at 500ppm and 1000 ppm concentrations against Pyricularia grisea following Poisoned Food Technique (Schimitz, 1930) [7] in vitro. All the tested fungicides significantly inhibited the mycelial growth at these concentrations. PDA medium amended with test concentrations of the fungicides. 1, Fig. 1 and Plate I).

Results were corroborated with Kurahashi (2001) [6] , when he experimentally proved that the details of new generation fungicides effective against blast of rice and pearl millet leaf blast and their mode of action. Lately, some fungicides which are target specific to Magnaporthe blast are reported.

In rice compounds like Tricyclazole [2] , Kumar and Singh (1995) [5] , Hossain and Kulkarni (2001) [4] and Gohel (2015) [3] .

Conclusion

Research has revealed variability in the efficacy of different fungicides against Pyricularia grisea. Some fungicides, such as Propiconazole, Difenconazole and Kasugamycin have demonstrated higher efficacy in controlling the pathogen.

References

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2. El-Kazzaz MK, Osman ZH, Sehly MR, Badr SS. Chemical control of rice blast disease. Agric. Res. Review. 1990;68:491-500.
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8. Vincent JH. Distortion of fungi hyphae in the presence of certain inhibitors. Nature. 1947;159:850.