Mapping Of Fon-1Gene Conferring Resistance To Fusarium Wilt In Cultivated Watermelon

Fusarium wilt, mainly caused by Fusarium oxysporum f. sp. niveum is a devastating disease of watermelon worldwide. This disease seriously aspects watermelon yields and fruit quality. Four races of F. oxysporum f. sp. niveurm have been identified and named as0,1,2,3, and race1is the predominant race in most areas of China. So mapping and cloning the gene which conferring resistance to Fon-1will be open new opportunities for controlling watermelon Fusarium wilt disease.In the previous study, we found the cultivated watermelon’Calhoun Gray’was highly resistant to F. oxysporum f. sp. niveurm race1, and its resistance was controlled by only one dominant gene Fon-1. The bulked segregant analysis (BSA) was employed to the Fon-1gene interval preliminary in watermelon. Series of candidate single nucleotide polymorphism (SNP) sites in which according the target traits were detected by sequence alignment within the target gene interval of11watermelon accessions. We develop respectively the cleaved amplified polymorphic sequence (CAPS) or derived cleaved amplified polymorphic sequence (dCAPS) markers closely linked with Fon-1gene by using231F2population and164cultivars. Base on watermelon whole genome information, we have carried on the annotation to preliminary Fon-1gene interval, and cloned the disease-resistant homologous genes than polymorphisms research. The main results obtained from this study are as follow:1. The Fon-1gene conferring resistance to Fusarium wilt race1in watermelon was mapped by bulk segregant analysis (BSA). We inoculate seedling and investigate the inheritance of resistance to race1through the F2segregation population. By using BSA with950molecular markers from watermelon, we have identified two markers WMG00291and197728_fon were linked with Fon-1gene, The Fon-1gene was delimited the genomic region15cM of watermelon chromosome1. The results of the study laid a foundation on Fon-1gene fine mapping. 2. Using bioinformatics methods, Fon-1gene was fine mapped. Series of candidate single nucleotide polymorphism (SNP) sites that are linked to the target traits, resequencing analysis within the target gene interval among11cultivated watermelon. And then, three markers7716_fon、7419_fon and4451_fon have been developed. The most tightly genetic distance between the marker loci and the Fon-1loci was estimated to be0.8cM. The results showed cleaved amplified polymorphic sequence (CAPS) markers7716_fon and7419_fon can be used as a universal marker for effective marker assisted selection (MAS) in watermelon Fusarium wilt resistance breeding.3. The candidate gene Fon-1was obtained. Base on watermelon genomic information, we have amplified over disease-resistant homologous genes between ’Calhoun Gray’ and ’Black Diamond’. Through sequenced alignment, SNP mutation has been found in coding regions of the FW-2gene. So we tentatively suggest that the FW-2gene as candidate gene of Fon-1.In conclusion, we have fine mapped the cultivated watermelon Fusarium wilt resistance gene Fon-1gene, and developed the CAPS markers which were tightly linked to Fon-1. The above results are not only provide platform for MAS of watermelon Fusarium wilt resistance breeding, but also provide foundation for further cloning of Fon-1gene in watermelon.