Vol. 6, Issue 2, Part A (2024)

Cabbage is one of the most important coli crops. Now it is grown almost throughout the year for its economic and nutritional value. India occupies 2nd position in cabbage production worldwide. It suffers from a wide array of fungal, bacterial and viral diseases which is causing severe loss in yield. Alternaria brassicae, the incident of leaf blight of cabbage is a fungal pathogen has been reported from all the continents of the world as well as in the state of Uttar Pradesh in wet seasons and in areas with relatively high rainfall. Symptomatology study revealed the seedlings developed spots on leaves leading to damping off. Initially small yellow specks are produced on leaves and stem which gradually darken and enlarge into circular, dark to tan coloured concentric rings giving a target board effect. In pure culture, the fungus produced profuse cottony mycelium, whitish to grey in colour at first and turned dark with age. The conidia are brownish black, obligate with 4-11 transverse and 0-4 longitudinal septa measuring 28.85-67.28×11.39-13.91µm with the average of 41.90×12.94µm. Conidiophores found to be distinctly geniculate arise in fascicles, dark brown unbranched, straight with 1-5 estate. Cultural studies revealed that Potato dextrose agar maximum growth (86.150mm) of the test fungus at 10 days of inoculation. The optimum pH for the growth of the test fungus was recorded to be 7.0 corresponding to maximum dry weight growth (360mg). The plate cultures of the fungus put under 16 hours of light along with 8 hours of darkness could facilitate highest radial growth (69.97mm) followed by the plates subjected to 12 hours light along with 12 hours dark (68.92mm), both being statistically at par with each other. From management study it was revealed that among the five phytoextracts evaluated, leaf extract of Datura at 20% concentration was found to be superior in inhibiting the mycelial growth (53.15-57.48%). Five biocontrol agents were tried in vitro against Alternaria brassicae in terms of the per cent inhibition of mycelial growth. Trichoderma viride (79.26%) found promising followed by Trichoderma harzianum (76.91%), both being statistically at par with each other. Eight agrochemicals were evaluated against Alternaria brassicae in terms of the per cent inhibition of the mycelial growth. Propiconazole at 0.15% was the best chemical resulting in significantly the maximum growth inhibition of the test fungus (100%) followed by Difenconazole showing 84.16% growth inhibition.