Deciphering the antifungal potential of giloy (Tinospora cordifolia (Willd.) Hook. f. & Thomson): GC-MS profiling of stem extract against Macrophomina phaseolina

Abstract

Macrophomina phaseolina, a necrotrophic fungus, causes multiple diseases in mungbean and other economically important crops worldwide. The pathogen remains in soil or crop residues for up to 3 years as microsclerotia. This study aims to identify alternatives to current conventional practices, which are limited and are associated with toxicity and resistance. Therefore, there is an urgent need to analyse the other eco-friendly alternatives also. The application of medicinal plant extracts has shown enormous antifungal potential against many sclerotial-forming phytopathogens. The present study tested five concentrations (10, 20, 30, 40 and 50 %) of nine different medicinal plant extracts against the per cent mycelial inhibition of M. phaseolina under invitro conditions. The results revealed that all the plant extracts showed significant mycelial inhibition at all concentrations compared to the control. The maximum per cent mycelial inhibition was recorded in giloy (70.5 %), followed by curry leaf (60.7 %), which was at par with eucalyptus (56.0 %), followed by lemon grass (50.8 %) and bhang (46.5 %) at 50 % concentration. The maximum level of total phenol (291 mg GAE/g) and flavonoid (179 mg QE/g) content was observed in giloy. The qualitative analysis of plant extracts indicates the presence of flavonoids, alkaloids, phenols and proteins. Gas chromatography–mass spectrometry (GC-MS) analysis of the giloy (Tinospora cordifolia (Willd.) Hook.f. & Thomson ) showed the presence of 32 phytochemical compounds, among which cyclopentadecanone was the predominant one with 28.45 % peak area followed by 2- bromododecane (25.93 %), palmitic acid, TMS derivative (10.78 %), 2-hexadeccen-1-ol,3,7,11,15-tetramethyl (5.04 %), 2-hexadecen-1-ol, 3,7,11,15-tetramethyl (5.04 %), tetracosane (4.88 %), hexanoic acid, 4-hexadecyl ester (4.12 %) and butylated hydroxytoluene (0.79 %). Some of these major compounds might be responsible for the antifungal properties of Tinospora cordifolia against M. phaseolina.  Under invivo conditions, all plant extracts significantly promote crop growth. The results depicted that the shoot and root length of mungbean varied from 45.6 to 51.1 cm and 20.6 to 24.7 cm, respectively, but the highest shoot and root length was recorded in giloy (51.1 cm and 24.7 cm), followed by curry leaf (50.2 cm and 24.1 cm). The plant extract also promotes the nodules formation, which ranges from 16.5 to 19.9 nodules/plant. Simultaneously, pod formation was greatly influenced and varied from 7.6 to 14.8 pods/plant. Both nodulations (19.9 nodules/plant) and pod formation (14.8 pods/plant) were greatly enhanced by giloy, followed by curry leaf. All the plant extracts showed a significant reduction in the disease incidence. Overall, the study signifies that the minimum per cent disease incidence (PDI %) was recorded in giloy (50.1 %), followed by curry leaf (52.5 %).