Phenotypic and genotypic diversity is essential and needs more enhancement in different ways to achieve higher productivity and better quality vegetables. The presented research aimed to study the phenotypic characteristics and determine the genetic diversity of F₁ populations compared with the colchicine mutant variants in the Mercy cultivar of cucumber (Cucumis sativus L.), held from March to May 2019 at the experimental field of the Department of Agrotechnology, Islamic University of Riau, Pekanbaru, Indonesia. A total number of 144 studied plants comprised 72 from each of the two plant groups. The data recorded on various parameters attained statistical analysis using paired T-test at a significant P < 0.05. Comparisons between the cucumber plants of both groups included karyotypes and chromosome shapes, idiograms, and sequencing. The results revealed that, on average, the taller plants came from F1 populations (93.49 cm), followed by mutants of the same cultivar (67.83 cm). The F₁ hybrids showed early flowering (29.00 days) compared with colchicine-treated mutants (33.31 days). However, the number of fruits and fruit weight were higher in the mutant variants (9.39 fruits and 1055.39 g), followed by F₁ populations. The karyotypes of cucumber cultivar Mercy F₁ hybrids and mutants have different chromosomes, especially with the arm size. An idiogram also exhibited differences in chromosome length between the variants of both plant groups, while the primers of trnL-F and trnL-R target sequences were the same with the DNA sequence length. Using mutant cucumber seeds demonstrates a change in phenotypic character to increase fruit production. However, polyploidy did not occur, with genetic alterations measured by the length of chromosome arms. As a result, a future study with increased concentrations of colchicine is imperative to obtain significant chromosomal mutations.

Keywords: Cucumber (Cucumis sativus L.), F₁ hybrids, colchicine mutants, growth traits, phenotypic characteristics, genetic diversity, chromosomes

Key findings: The number of fruits and fruit weight were higher in the mutant populations, while the Brix values and plant height were better in F₁ hybrids compared with the mutants in cucumber (Cucumis sativus L.). The varied karyotypes between F₁ and mutant populations with short-arm (p) and long-arm (q) size indicate significant differences in the number of genes. The variation in chromosome arm length phenotypically causes changes in the morphological characters. Therefore, it is necessary to enhance the colchicine concentration and immersion time to obtain polyploidy.