关键词: 西瓜, 四倍体, 枯萎病生理小种1, 抗性, 分子标记辅助选择

Abstract: Based on the molecular markers tightly linked to Fon-1 for Fusarium oxysporum f. sp. niveum race 1 resistance in the diploid watermelon developed in our laboratory，the fine mapping of Fon-1 was finished in this study. A backcross population of susceptible recurrent parent NF3 and resistant donor parent JH was constructed. The newly developed SNP marker was used for Fon-1 resistance marker- assisted selection and seedling inoculation identification in different generations. The results showed that the ratio of resistant plants post-inoculated was 12.64%–15.34% lower than the ratio of resistantgenotype detected by molecular marker. The reason is that because of gene dosage effect，different heterozygosity genotype have different resistance in tetraploid watermelon as follow：AAAa > AAaa > Aaaa. At present the molecular marker could not detect the gene dosage effect or identify the susceptible genotype Aaaa. In the 673 plants BC1F2 population，we detected 29 homozygous resistant genotype（AAAA），accounting for 4.31% of the total number of plants. All of the 29 homozygous plants showed Fon-1 resistance by screening with inoculation of Fon race 1.

Key words: watermelon, tetraploid, Fusarium oxysporum f. sp. niveurn race 1, resistance, molecular marker-assisted selection