Abstract: Strawberry nucleus suspension of high purity was essential in order to improve the accuracy of flow cytometry， to obtain reliable testing data with a small coefficient of variation （CV value） and to provide technical support for the strawberry ploidy breeding. Objective to find the optimal preparation method of strawberry nucleus suspension， polidy determinations of diploid Chuanjiu No.1 and octoploid Hongjia strawberries were conducted with flow cytometry using different filtration methods and OTTO extraction buffers. The results showed that the optimized filtration method was the two\|step filtration method （70 μm and 40 μm apertures）. OTTO Ⅰ ［100 mmol·L-1 citric acid， 0.5% （V/V） Tween20 and 2% （V/V） PVP， pH 2～3］ and OTTO Ⅱ （400 mmol·L-1 Na2HPO4·12 H2O， pH 8～9） were found to be the optimal extraction buffers. Strawberry nucleus suspension prepared by the optimal method was analyzed by flow cytometry， and it showed a narrow， focused histogram with a small CV value of 5.43%.

Key words: flow cytometry, strawberry nucleus dissociation, CV value