QTL Analysis Of Round Stamens In Watermelon

Watermelon（Citrullus lanatus L.）is a popular horticultural crop,dioecious and annual creeping vine.Watermelon contains a variety of vitamins and rich mineral salts,and is the main fruit to beat the heat.As the male reproductive organ of angiosperms,stamens are the places where pollen is produced,which plays an important role in the reproduction of plants,and its morphological changes have a certain impact on the development of pollen.In this study,the loose stamens watermelon variety’1061’was used as the mother and the round stamens watermelon variety’812’was used as the father,and the F₁and F₂generation groups were prepared to investigate the morphology of the stamens of each generation,and microscopic observation of watermelon stamens and determination of pollen viability were carried out.At the same time,on the basis of BSA,the parent resequencing data was used to develop CAPS molecular markers,and the F₂generation isolated population phenotypic data combined with CAPS markers was used to construct a genetic linkage map and carry out the morphological gene mapping of watermelon round stamens,in order to provide a certain theoretical basis for the morphological development and resource improvement of watermelon male flowers.The test results are as follows:（1）Through field the statistical observation and analysis,the stamens morphology of watermelon showed a normal distribution in the F₂generation population,and the stamens morphology was a quantitative trait controlled by multiple genes.（2）Using acetate magenta dye solution,the number of pollen and vitality of round stamens were significantly higher than that of scattered stamens.（3）Paraffin section and transmission electron microscopy of the unopened male flowers of both parents showed that the size of the round stamens and the scattered stamens chamber were significantly different,and the area,length and width of the cross-section of the round stamens were larger than those of the scattered stamens.（4）Plants with round stamens and scattered stamens were selected from the F₂generation population and divided into two groups,two extreme trait DNA pools were constructed,and the genes controlling round stamens were mapped to chromosome 1 28736061 bp-31284534 bp（about 2.55 Mb）and the 15285954 bp-16361731 bp（about 1.07 MB）,33564909 bp-34143475bp（about 0.58）of chromosome 9 MB).（5）A genetic linkage map including 34 pairs of CAPS markers was constructed by using242 F₂surrogate groups,including 2 linkage groups,the length of linkage groups was 291.33cM and 261.43 cM,containing 20 and 14 pairs of CAPS labels,respectively,and the average distance between each CAPS marker was 14.56 cM and 18.67 cM,respectively,corresponding to two chromosomes number 1 and 9,respectively.（6）According to the results of BSA analysis,the CAPS marker was further developed and screened using parental resequencing data,combined with the stamens morphology of the F₂population,and the main QTL site controlling round stamens was screened on chromosome 1,located between the CL1＿31059247 and CL1＿31584361,at a physical distance of 525.11 kb,named FT1.（7）According to the watermelon reference genome 97103（version v2）information,the gene function annotation of 82 candidate genes in the interval FT1 was carried out,and the screening found that 2 of the candidate genes had nonsynonymous mutations,respectively,the gene annotation of Cla97C01G017570.1 was Methylmalonate-semialdehyde dehydrogenase,andthegeneannotationofCla97C01G017980.1wast RNA（Cytosine（34）-C（5））-methyltransferase,possibly related to the morphology of watermelon round stamens.