The influences of genotypes,gamma ray doses and dose-rate on the induced haploid embryos obtained

by irradiated pollen with different ray doses were studied in squash(Cucurbita pepo L.).Different embryo

shapes and development stages were found in seeds extracted from fruits cultured in medium E20A.The results

indicated that the rate of plants regeneration and haploid production were strongly influenced by

genotypes,embryo stages and gamma ray doses.The highest percentage of haploid production was 1.30 % for

genotypes 281.Point and arrow-like embryos were more likely to produce haploid plants.Meantime the percent of

point and arrow-like embryos and the numbers of all embryo shapes were the highest when their ray doses were

80-100 Gy.Stick-shape embryo gave the best result,in which the plants regeneration rate and survival

percentage were 83.33 % and 35.71 %,respectively.The optimum dose-rate was 45.19 Gy·min^-1.