Phosphite impact on the in vitro production and viability of selfed oospores by Phytophthora cinnamomi

Summary Four isolates of Phytophthora cinnamomi were able to produce selfed oospores when cultured in vitro on modified Ribeiro’s minimal medium. Phosphite inhibited the production of selfed oospores at 100 μg phosphite/ml, lower concentrations had no effect. Selfed oospores were considered dormant as 16–47% of selfed oospores were found viable using viability staining techniques such as thiazolyl blue tetrazolium bromide and 4′,6‐diamidino‐2‐phenylindole·2HCl yet they did not germinate on a range of media. Phosphite up to 100 μg/ml did not change the proportion of viable selfed oospores. This study shows that phosphite does not affect the production of selfed oospores.