Effects of pH, media composition and temperature on growth and sporulation of Alternaria lini
Abstract
An experiment on effect of various substrate composition, atmospheric temperature and substrate pH on growth, development and sporulation of Alternaria lini. The pathogen was collected from linseed growing areas of Hamirpur district of Uttar Pradesh during rabi 2013-14. Four growth media of various compositions were prepared as suggested by various workers. For the study of the effect of different pH levels, Potato dextrose agar medium was used and adjusted at different pH levels viz. 3.5, 4.5, 5.5, 6.5, 7.5, 8.5 and 9.0 with the help of Phillips pH meter by using N/10 hydrochloric acid and sodium hydroxide solution for the maintenance of pH. Inoculated Petri plates were kept in incubators set at the temperatures (l0, 15, 20, 25, 30 & 350 C) for 7-10 days. Three replications were used for each treatment. The cultures were examined after 7 - 10 days of incubation for minimal growth, normal growth and maximal growth. The observation were recorded and tabulated as per standard procedures. The results showed that the highest radial growth of 33mm was recorded from potato dextrose agar (PDA) media. The further superiority sequence of the media was as Oat Meal (Richard's agar), Corn Meal agar (Czapeck (Dox) agar, Malt Extract agar respectively with the radial growth of pathogen colony in the order 30 mm>27 mm>24 mm>21 mm>18 mm respectively. The results also revealed that Malt extract agar was poorest among the six culture media undertaken for present study. The maximum growth of the pathogen was observed at 250 C with maximum radial growth of 36 mm followed by 30 0C with 26 mm radial growth. The growth of the pathogen was significantly decreased to 10- 22mm at 200 C, 150 C and 100 C. At higher than optimum temperature 350 C, growth decreased rapidly and was just 11 mm in diameter. The pathogen grow over a wide range of pH ranging from 3.5 to 9.0 but the maximum growth in the tune of 35mm with excellent sporulation was recorded at pH 6.5 followed by 7.5 with radial growth of 31.5 mm. The growth was progressively decreased at 5.5 (21mm), 8.5(20.5mm), 4.5 (14mm) respectively. The media with maintaining pH 9.0 and 3.5 showed the minimum radial growth of the pathogen 8mm and 8.5mm respectively indicating the adverse effect of pH on radial growth of colony and behavior of sporulation.
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