Marker-assisted Development Of Near-isogenic Lines For Little Leaf Introgression Into Different Genetic Backgrounds Of Cucumber (Cucumis Sativus L.)

Cucumber(Cucumis sativus L.),2n=2x=14,is an annual vining crop of cucurbitaceae family,which is one of the most important vegetables in the world.With the completion of the whole genome sequencing of cucumber,it provides great convenience for marker-assisted breeding,gene mapping and functional verification,and others.Molecular marker-assisted is widely used in crop breeding.Because of its special genetic composition,near-isogenic lines have become ideal materials for research gene functions,development of molecular markers,etc.Recurrent parents are the North-china fresh cucumber 9930 and the gynoecious determinate cucumber line Gy14,the donor parent is the monoecious indeterminate little leaf line H19.Development of near-isogenic lines for little-leaf introgression into genetic background using once cross,twice backcrosses,once self-crossing,and three molecular marker-assisted selections.The following results were obtained:1.Based on the parental combinations of 9930×H19 and Gy14×H19,there are 102 pairs of SSR markers and 88 pairs of SSR markers were used for molecular marker assisted of background selection from 288 pairs of SSR markers covering the whole genome of cucumber,which were evenly distributed on 7 chromosomes of cucumber.The average distance between the two markers was 1.61 Mb and 2.18 Mb respectively,and the marker density was moderate,which was suitable for the background selection of each generation.2.To development of near-isogenic lines for little leaf,the d CAPS marker co-segregation with target gene was uesd for foreground selection,the whole genome of candidate individual plants were selected in BC1F1,BC2F1 and BC2F2 population by using above 102 and 88 pairs of SSR markers.In the 9930×H19,54 candidate indicidual of BC2F2 were obtained for the development of near-isogenic line under the 9930 genetic background.In the Gy14×H19,the individual plant with a high PRPG was selected among the 43 candidate plants in BC2F1 for the next-generation self-crossing.3.Results of analysis of candidate indiciduals graph of each backcross generations:in the 9930 genetic background,PRPG of the BC2F1 and BC2F2 has been highly restored,with an average of PRPG are 90.2% and 92.22%,respectively.This results are consistent with expectations.The average of PRPG with BC1F1 and BC2F1 are respectively 66.45% and 69.19% in Gy14 genetic background,and BC2F1 population were selected for the next-generation genetic background recover.In this study,using marker-assisted selection to rapidly development of near-isogenic lines for little leaf introgression into different genetic backgrounds,which will provide the material basis for through study of little leaf function and mechanism of organ size regulation,and at the same time will provide genetic resources for reserch of cucumber fruit size.