Inhibition of urediniospore germination in Puccinia hemerocallidis by Bacto Agar and changes in percent germination and germ-tube elongation on agarose over time

摘要

Agar is a commonly used gelling agent and a raw material used in other gelling agents. The effects of five gelling agents and potato dextrose agar on urediniospore germination, and changes in percent urediniospore germination and germ-tube elongationin Puccinia hemerocallidis over time were investigated in vitro. Percent urediniospore germination differed significantly between the tested gelling agents. Urediniospores germinated well on Gelrite, agarose, Phytagar, and Oxoid No. 3 agar in decreasingorder, and percent urediniospore germination was negatively correlated with the concentration of gelling agent. Urediniospores germinated poorly on the substrates containing more than 0.5% Bacto Agar. The concentration of Bacto Agar that caused 50% inhibition of urediniospore germination was 18.2 g/mL in 1% agarose substrate. However, there were no significant differences in germ-tube elongation between the concentrations of Bacto Agar water extract tested. Unidentified inhibitory compounds from Bacto Agar water extract were adsorbed on a C18 column and the effluent water did not affect spore germination. However, the methanol-eluted solution from the C18 column completely inhibited urediniospore germination when the solution was evaporated and reconstituted with water. Changes in percent urediniospore germination and germ-tube length on 1% agarose water substrate over time fitted well with negative exponential models. The time to the half-asymptote of percent urediniospore germination and germ-tube length was 1.4 and 6.0 h, respectively, and the time to 95% of the asymptote was 6.1 and 30.9 h for spore germination and germ-tube elongation, respectively.