Identification And Gene Mapping Of A White Immature Fruit Skin Color Mutant Gene In Cucumber (Cucumis Sativus L.)

The immature fruit skin color of cucumber（Cucumis sativus L.）is an important exterior quality character,influencing the choice of consumers.Currently,the green fruit skin color varieties of cucumber are the main cultivars;however,the white fruit color varieties are very few in the market.With the diversified development of the consumer requirements,more and more different fruit skin color varieties of cucumber are demanded,and the white as well as the halftone between white and green fruit skin color is gradually favored by people.Genetic improvement of cucumber fruit skin color traits will become one of the goals to the breeding of cucumber exterior quality.Genetic analysis and gene mapping of the white fruit skin color trait and the regulation gene are the foundation to the studies of the fruit colors.A white skin color mutant（namely M33）has been found from a huge quantity of green skin color cucumber plants（W33）when conducted the breeding work in our previous research.After several generations of breeding,the white skin color trait is turned to be stable.Herein,we conducted the genetic analysis of the fruit color trait,and gene mapping of target gene（mw）.Finally got the main results bellow:1.Constructing 6 generations of genetic populations by W33 and M33 to conduct the genetic analysis of the white fruit color trait of the mutant,and the result showed that the mutant white skin color is controlled by a single recessive nuclear gene（mutant white,named mw）.2.Using the F₂ segregated population（about 1800 from “9930” × M33）and the SSR markers to conduct gene mapping,and finally mapped the target mw gene to a 2.2 cM region on chromosome 3,which was flanked by SSR21652 and SSR10603 with a physical interval of 60.1 kb.3.The main agronomic traits showed significant difference between the parent lines by comparing the height of the plant,the diameter of the stem,the vertical and horizontal diameter of the fruit,etc.4.Polymorphic analysis of the whole genome microsatellite marker（SSR）sequences showed that there are 3,0,33,13,20,41,18 polymorphic SSR markers detected on each chromosome of cucumber between W33 and M33 by performing the whole genome analysis.5.To verify the relationship of the gene sites of the gene mw and w,other two white fruit skin color materials（Q24 and B-2-2）were chose to build the verification populations（F₁ and F₂）together with M33.The F₁ and F₂ phenotype of M33 × Q24,M33 ×B-2-2 and Q24 × B-2-2 demonstrated that the mw is probably a mutant allele of w,which controls the normal white skin color in cucumber.