Extraction from Plant Tissue and Germination of Oospores of Peronospora viciae f.sp. pisi

A protocol was developed to extract oospores of Peronospora viciae f.sp. pisi from plant tissue and control bacteria! contamination in a germination assay. Oospores were extracted by comminuting infected leaves and pods in water, sonicating the suspension and sieving it through mesh sizes 53 and 20 /im, respectively. Germination of oospores was negatively influenced by addition of chloramphenicol and penicillin. A combination of ampicillin and rifampicin strongly inhibited bacterial growth at 10"C, and did not negatively affect germination. Washing oospores in water or 0.02% Tween-80, and sonication did not infitience germination. Treating oospore suspensions with cellulase buffered at pH 4.6 for 2 h digested most plant tissue but did not influence germination. Incubation in 0.05 m acetate bufler delayed germination. Germination was unaffected when oospores were incubated in 0.05 m citrate buffer.