Utilization of marker-assisted backcrossing to generate new gynoecious cucumber lines with genetic heritage similar to the indigenous Vietnamese cucumber

The marker-assisted backcrossing (MAB) can help to transfer an interested allele at a target locus from a donor to a recipient line. Gynoecious is a pivotal trait of cucumber since commercial F₁ hybrid seeds produced with gynoecious line as one of the parents are high-yield and affordable. This study aims to transfer the F locus encoded for gynoecious trait to Vietnamese domesticated cucumbers by marker-assisted backcrossing. Two monoecious cucumber lines, A₁ (Ha Giang, Vietnam) A₂ (Yen Bai, Vietnam), and two gynoecious cucumber lines, B₁ (Plantgene, India) and B₂ (Hue, Vietnam) were utilized as the starting materials. BCAT marker (located on the F locus) and 52 SSRs (spread across seven chromosomes and tightly linked with some crucial horticultural traits) were used as the foreground and background markers, respectively. With this, phenotype selection for fruit and leaf sizes was also applied. First, using phenotypic screening and foreground marker, A₁ (Ha Giang, Vietnam) and B₁ (Plantgene, India) were selected as donor and recurrent parents for backcrossing. Then, after two backcrosses followed by two self-pollinations, four gynoecious C cucumber lines were created. These C lines have leaf sizes slightly bigger than the recurrent parent. Importantly, their fruit length is the same or longer than A₁ (Ha Giang, Vietnam). These new gynoecious lines could be used as material lines for producing commercial F₁ hybrid seeds.