Effect of Some Inorganic Salts and Hydrogen Ion Concentration on Indirect Germination of the Sporangia of Phytophthora infestclns.

Abstract

XNrhen the spoFangia ef RP4))tophtho?zi iidestans washed twice in distillecl water were tested for indirect germination at 140C, they did not germinate well (9% in 3 hr) in distilled water, while in the tap water of Hokkaido Natl. Agric. Exp. Stn., they germinated well (78% in 3hr). Since some inorganic ions in the tap water appeared effective, various concentrations {O.Ol-10mM) of the salts, CaCl2, Ca(N03)2, MgC12, MgSO4, KCI, K2S04, NaCl and Na2S04, were evaluated for the effectiveness on indirect germination. SporangiaL suspensions were preincubated for 22 hr at 22"C for sporangial maturation and postincubat- ed at 14"C for indirect germinatjon. The most effective solution was e.3 mM CaC12 (71% germination in 1 hr), followed by O.3 mM )ilgSO, (65%). Potassium and sodium salts were not very effective (<2396). At the catien concentration of 10 mM a]1 the salts except Na2SQ, inhibited indirect germination (O-5%). Hydrogen ion concentration markedly affected indirect germinatien, optimuin at pH 8.0 (9e% germination at O.1 mM CaC12) but completely inhibitory at pH 4.5 (O%), Considering the results and the cations contained in the tap water, a synthetic salts solution favorable for indirect germination was devised: U.2 mM CaCl2, O05 mM MgSO,, O.05 rnM K}I2PO,, O.5 mM NaHC03, O.Ol mM Fe-EDI"A-Na. Using t,his solution the effect of sporangial concentration on indirect germination was also investigated. Sporangial suspensions beLow 2.5× le" sporangiafml were favorable for indirect germination (). 97% in 2hr) but those above 10S were not.