Cucumber F1 hybrid derived from two contrasting inbreds ensures high frequency gynogenesis for induction of haploids through a modified in vitro based protocol

• Published in: South African journal of botany 2023-06, Vol.157, p.314-324
• Main Authors: Pradeepkumara, N., Dey, S.S., Munshi, A.D., Behera, T.K., Bhatia, Reeta, Kumari, Khushboo, Prakash, Pragya, Bhattacharya, R.C., Talukdar, Akshay
• Format: Article
• Language: English
• Subjects: Cucumber; Flow cytometry; Gynogenesis; Haploids; Heterosis; Shelf-life; Sucrose concentration; Temperature shock treatment
• ISSN: 0254-6299; 1727-9321
• DOI: 10.1016/j.sajb.2023.03.066

•Demonstrated the better suitability of F1 hybrid for gynogenesis and induction of haploids for the first time.•Flow cytometer confirms high frequency of induced haploids through gynogenesis.•This study establishes the suitability of polymorphic SSRs in detection of haploids from an F1 hybrid.•Significant heterosis for all important parameter of gynogenesis was recorded across the treatments which is first of kind information in vitro gynogenesis of any plant species.•Higher sucrose concentration and combined pre-treatment with cold and heat shock treatments were very useful for induction of large number of ELS. The present study was undertaken to develop an efficient protocol in cucumber for induction of large number haploids through gynogenesis and to understand the effects of heterosis on gynogenesis. One natural variant, DC-48 with exceptionally high shelf life along with another genotype, DC-83 with very low shelf-life and the F1 hybrid using these contrasting parents were used donor mother plants for in vitro gynogenesis. Effects of developmental stages, plant hormones, sucrose concentration and combined cold and heat shock pre-treatment were studied. For the first time, we are reporting significant heterosis for important parameters of gynogenesis using a F1 hybrid and their corresponding parental lines as donor genotypes. Unpollinated ovules cultured at one day prior to anthesis was most suitable developmental stage for efficient induction of embryo like structures (ELS) and haploids. Basal MS based media supplemented with 5.0 mg/L Zeatin and 0.2 mg/L NAA was most effective in induction of large number of ELS in all three genotypes. A combination of low temperature pre-treatment and high temperature heat shock treatment after culture was very useful in formation of ELS. Cold pre-treatment at 9 °C for 4–6 days followed by heat shock treatment at 32 °C for 2–4 days were ideal temperature shock treatment for high frequency direct regeneration. A large set of polymorphic and uniformly distributed SSRs were used to confirm hybridity and allelic distribution of the developed plants through gynogenesis using F1 hybris as mother plant. The ploidy level determined through flow cytometer validated the SSR based detection of ploidy level. This novel approach was suitable in identifying the plants developed from female gametocytes. It was interesting that all the regeneration related traits exhibited significant heterosis in desirable direction across the trea