2.4. Growth study

Mycelial growth of the Halophytophthora isolates under various combinations of temperatures, pHs and salinities were measured based on a microtitre plate (Co-Star 3595, Corning, Maine, USA) method designed by Langvad (1999). A medium containing 4 g/L glucose, 4 g/L yeast extract and 4 g/L peptone was used as the growth medium and 180 μl of this medium adjusted to various pHs (6, 7, 8) and salinities (4 ‰, 8 ‰, 16 ‰, 32 ‰ made by sea salt) were dispensed into wells of the microtitre plate. Acidity/alkalinity of the medium was adjusted using hydrochloric acid (Taiwan Green Version Technology Ltd., New Taipei City, Taiwan) and sodium hydroxide (Panrea, Barcelona, Spain). The spore suspensions (20 μl) were added to the wells and mixed briefly. For each treatment, four replicates (wells) were done. The inoculated plates were incubated at 15°C, 25°C and 37°C. A set of control wells for each treatment, i.e. the growth medium with no spores, was also prepared. Absorbance of the wells of the microtitre plates was measured daily at 630 nm using the multi-detection microplate readers (Synergy HT, BioTek) for 9 days. Growth of the isolates was represented by subtraction of the absorbance of the inoculated wells to that of the control wells.