Association Analysis Of Agronomic Traits With SSR Markers And Genetic Dissection Of Particular Accessions In Melon(cucumis Melo L.)

With abundant germplasm resources,melon possesses a hugely wide collection of phenotypic variation.The understanding of genetic mechansim of argronomic traits will be very useful to the melon breeding.Molecular marker technology and bioinformatics method are widely employed in QTLs mapping and analysis of genetic diversity.62SSR markers and 8 traits were chosen to make association analysis on 144 melon accessions,and a number of markers associated with targeted traits have been discover.Then we developed an InDel marker associated with flesh color by sequence alignment.Our purpose is to find or develop markers which have the potential to play roles in molecular marker selection of melon.In the meantime,we expect the rapid prediction and selection of melon phenotype and the combination of different phenotypes.Finally,we’d like to make an effort to accelerate the relization of fine breeding in melon.The major aspects of this study are as follows:1.Statistical analysis on 144 melon accessions of three cropping seasons showed that the phenotypic variation was hugely manifold.There were 16 traits investigated and analyzed,among which the diversity range of 8 qualitative traits was 0.36-2.29,and the average is 1.16.There were 8 quantitative traits whose coefficient of variation changed from 10.0%to 49.0%,and average fruit weight showed the highest value.The mean values of average fruit weight in three cropping season varied from 25.67 g to1937.33 g,the total mean value was 910.84 g.The maximum value of average fruit weight was 74.5 times as much as the minimum value.Together with the coefficient of variation which was 0.49,they made the highest values of all trait data.It suggested that the collection we selected exhibited a hugely wide genetic diversity in fruit traits.2.We obtained a number of markers associated with some traits by the regression analysis in 144 melon accessions.There are 69 loci significantly associated with 8 traits（p<0.01）,averagely each trait was associated with 8。6 loci.Average fruit weight had18 associated loci which was the most of all traits.LG1 gathered 10 associated loci which is the most of all linkage groups.Then we performed association analysis in 64muskmelon accession from the melon collection by using the same 62 markers.There were 49 associated loci discovered under p<0.01 significant level,averagely each trait got 6.1associated loci.Both unisexual flower and total sugar content had 13 associated loci which was the most of all traits.LG 9 gathered 7 associated loci which is the most of all linkage groups.It will be useful for the application of MAS in melon breeding and provide basis for the development of new varieties using molecular markers.3.According to the alignment between the nucleotide sequences of CmOr in orange versus green/white flesh fruit,we discovered an insertion/deletion in the intronic region where orange flesh melon have 72 bp size insertion compared with non-orange flesh melon.We developed an InDel marker and designed a pair of primers based on the sequence near this region to screen melon with orange flesh.Theoretically,the polymorphism of this InDel marker is supposed to cosegregated with the flesh color.We genotyped 28 melon accessions with different flesh colors using the primers and screened orange flesh melon accessions accurately.Then we constructed F₂ populations to realize the transfer of orange fruit,the predictive accuracy are all over 93%.Our research selected 50 muskmelon accessions to verify an InDel marker which was potentially associated with rind color.The total accuracy of the identification was84.0%.It shows that this InDel marker can be used in the melon breeding.