STUDY ON PHYSICOCHEMICAL FACTORS ON THE GROWTH AND SPORULATION of Alternaria alternata AND Alternaria brassicae

Bacopa monnieri and Aloe vera are two highly important medicinal plants. To enumerate the role of environmental condition and it’s effect on infection and survival of the pathogen, it’s necessary to determine the optimal growth condition of the isolated pathogens - A. alternata (leaf blight disease of Bacopa monnieri) and A. brassicae (Leaf spot disease of Aloe vera) in different media, temperature and pH. The radial growth, biomass production and sporulation of the pathogens in solid and broth media of Potato Dextrose, Potato Carrot, Czapek Dox and Host Extract have been monitored. It was found that radial growth and biomass production were highest in PDA and PDB for A. brassicae (7.20 cm & 0.976 gms) and A. alternata (7.65 cm & 0.987 gms). The sporulation for A. alternata (15×104 /ml) and A. brassicae (8×104 / ml) were maximum in PCB. Among the range of temperature used 10-35°C, 30°C temperature were found suitable for the radial growth ,biomass production and 25°C for sporulation of A. brassicae (8.85 cm, 1.350 gm, 3×104 / ml) and A. alternata (9 cm, 1.400 gm, 4×104 / ml). Where as pH 6.5 was the ideal pH for the radial growth and biomass production of A. brassicae (8.85 cm & 0.956 gms) and A. altarnata (9 cm & 0.942 gms). A. alternata recorded with 4×104 / ml where as A. brassicae with 3×104 / ml no. of spores at pH 5-6.5 as ideal pH. But at most of the given conditions, A. alternata exhibits more radial growth, biomass production and sporulation in comparison to A. brassicae.