Development of cucumber autotetraploids and their phenotypic characterization

Abstract

Polyploidy induction is expected to increase its breeding potential. Cucumber, Cucumis sativus L. (2n=2x=14), is one of important vegetable worldwide. The objective of this work was to develop autotetraploids three ecotypes of cucumber through colchicine and to reveal their phenotypic characterization. Autotetraploid plants were produced by colchicine using the treatment method to shoot apexes of seedlings with different concentrations (0, 0.1%, 0.2%, and 0.3%) and treated times (3, 5 and 7 applications). The treatment with 0.2% colchicine for 5 or 7 times and 0.3% colchicine for 5 times were proved to be more effective in producing autotetraploids. Candidate polyploids were preliminarily screened by morphological characteristics and stomatal apparatus, then detected by flow cytometry and confirmed by chromosome counting. As expected, the chromosome number was 2n=2x=14 in diploids, and 2n=4x=28 in the autotetraploid. The genome size was not altered in the second-generation progeny from all plants analyzed by flow cytometry. The tetraploid plants were accompanied by larger leaf size, flower diameter, stoma size, pollen grains and more chloroplast number in guard cell, but decrease in stoma, fruit size, and percentage of normal pollen. This study established an efficient method for the induction and identification of autotetraploids in cucumber.