Vol. 10, Issue 7 (2021)

Author(s):
Ann Tom and SI Patel

Abstract:
Fusarium verticillioideshave distinct host - pathogen association with maize.Dynamics of disease from necrotrophic pith disintegrating and slow evading soil inhabitant to harmless endophytic association was unravelled in different inoculation techniques. Internodal region of maize stalk as dominant niche of post flowering stalk rot inducing F. verticillioides,when subjected to isolation in potato dextrose agar expressed white fluffy mycelium turning purple in incubation. Microscopic observation recorded few single septate and abundant aseptate oval shaped micro-conidia from monophialides, macro-conidia were falcate shaped and were observed to be rare. Chlamydospores were absent. Several artificial inoculation techniques were implied to analyse the varying response of the plant with respect to different inoculation sites, age and method of inoculation. Toothpick method of inoculation expressed typical post flowering stalk rot symptoms indistinct to farmer’s field and recorded highest percent disease intensity of 89.63. Pith disintegration in toothpick inoculation technique was supplemented by injury, susceptible reproductive stage and internodal stalk region of maize. Hence, toothpick method of inoculation of F. verticillioides was indicated as an ideal technique for the laboratory analysis of disease. Underdeveloped plants with rotten roots, slight pith discolouration and 5.18 percent disease intensity manifested in soil inoculation technique indicated slow above ground growth of fungus along with its soil inhabiting nature. Endophytic association of F. verticillioides with maize during absence of stress was revealed in spore injection technique with zero percent disease intensity. Pith disintegration and mycelium infected cobs induce disease severity of post flowering stalk rot of maize. Efficacy of different fungal and bacterial antagonists were tested against the mycelial growth of F. verticillioides using dual culture technique. Trichoderma harzianum isolates recorded higher growth inhibition exceeding 70 per cent. Growth inhibition of Trichoderma viride isolates ranged from 51.48 to 64.07 per cent.Sardarkrushinagar isolates of T. harzianum and T. viride exhibited superior reduction. Bacillus subtilis and Pseudomonas fluorescens recorded 61.86 and 43.70 per cent inhibition. These free living bio-agentsbeing highly interactive in soil, root and foliar environment serves as an effective biopesticde for the control of F. verticillioides in maize.