Molecular Marker Assisted Selection For Excellent Traits And CsSH1 Gene Editing Application Of Xishuangbanna Cucumber

Cucumber（Cucumis sativus L.）is an annual creeping or climbing herb of Cucurbitaceae.As an important vegetable crop,it is widely cultivated all over the world.Among them,China’s cucumber planting area,yield and per capita annual consumption are ranked first in the world.Due to the narrow genetic basis of cucumber,the traditional breeding cycle is long and the efficiency is low,which seriously hinders the progress of cucumber genetic breeding.Therefore,it is imperative to use biotechnology to improve cucumber.Xishuangbanna cucumber（Cucumis sativus L.var.xishuangbannanesis Qi et Yuan）is a semi wild variety resource of Cucurbitaceae,which has many special characters superior to common cucumber,such as orange flesh,the number of fruit ventricles,short hypocotyl.Therefore,Xishuangbanna cucumber plays an important role in broadening the genetic background of cucumber,which can provide theoretical basis for genetic improvement and breeding of cucumber and other cucurbitaceous crops.Based on this,this paper aims to use biotechnology and excellent characters of Xishuangbanna cucumber for directional improvement of cultivated cucumber.Using molecular marker assisted selection technology,the characters of multi ventricle,orange flesh and short hypocotyl were transferred into‘Wynia-inbred’,‘EC1’and‘Yixiu weak female’,and the short hypocotyl Cs SH1 gene editing vector was transformed into‘CCMC’by gene editing technology.The specific research contents and results are as follows:1.Molecular marker assisted selection of the traits of multiple carpels,orange pulp and short hypocotylsBased on the multi ventricular trait markers were UW083751,SSR04278,orange pulp traits were SSR15419,SSR07706,SSR3231,SSR11633 and short hypocotyl traits was sh-d CAPS-51,which were developed in the laboratory.In this study,the donor parent‘SWCC8’and the recipient parent‘Wynia-inbred’,‘EC1’and‘Yixiu weak female’were used to verify the polymorphism of seven candidate markers,and five available molecular markers were screened,namely SSR04278,SSR07706,SSR3231,SSR11633 and sh-d CAPS-51.Then,on the basis of previous studies on backcross generation,using breeding marker assisted selection of excellent individual plants,combined with the observation of field agronomic traits,seven intermediate materials with excellent traits were selected from three backcross improved populations,namely 20499F-5,20499F-12,20499F-16,20499F-63,20486F-4,20486F-47 and 20487F-63,and the breeding process was extended for one generation.2.Gene editing of short hypocotyl Cs SH1 geneUsing CRISPR/cas9 system,the Cs SH1 gene editing vector was transformed into‘CCMC’,which was not tolerant to overgrowth,and four positive transformed seedlings were obtained.The results showed that SH1-2 and SH1-3 were transgenic plants,and the two target sequences were edited.The phenotypes of T₁generation SH1-2 and SH1-3 were observed.The hypocotyls of SH1-3-4、SH1-3-5、SH1-3-6、SH1-3-19 and SH1-3-21 were short and strong.This study can provide research ideas and methods for directional improvement and genetic breeding of cucumber to a certain extent by using the excellent characters of Xishuangbanna cucumber through molecular markers and gene editing.