Survey and Pathological Investigationon Fusarial Wilt of Garmalo(Cassiafistula L.)

Occurrence of fusarial wilt of garmalo (Cassia fistula) was conducted in three districts of Southern Gujarat. The maximum percent disease incidence (75 per cent) was observed at Karatha Sarvajanik Forest Nursery of Narmada district. Microscopic examination and the tissue isolation from roots of infected seedlings of different forest nurseries yielded culture of Fusarium oxysporum. Most of the plants were found infected by showing varying degree of infection indicating their susceptibility to the pathogen at almost all stages of seedling growth. Leaves became yellow with initially brown and eventually black streaks in the vascular system. Plants were showing severe stunting and initiation of wilting symptoms and at later stage found to be completely wilted. On critical examination, the fungal growth was observed on the roots of the wilting plants. Microscopic examination revealed the presence of micro and macro conidia of F. oxysporum with dirty white mycelium. The pathogenicity tests were carried out by soil inoculation, seed inoculation, seed cum soil inoculation, and root dip inoculation in plastic pots. All the methods successfully produced typical wilt symptoms similar to those observed under natural condition and described in the literature, confirming pathogenic nature of the fungus. Among the different techniques root dip inoculation method was found to be the quickest and most effective method for proving the pathogenicity followed by seed cum soil inoculation and soil inoculation method. Thus, the causal agent of the Garmalo (C. fistula) fusarial wilt was identified and confirmed as Fusarium oxysporum.