In vitro regeneration of hybrid squash (Cucurbita pepo L.) cv. First Runner from cotyledonary node explants

Abstract

Squash (Cucurbita pepo L.) is highly polymorphic in nature which could con- tribute its different regeneration potentiality for different genotypes. The present investigation was carried to know the effects of plant growth regulators, explant types, explants age and AgNO₃ on in vitro regeneration potentiality of hybrid squash genotype and to optimize regeneration protocol. In this protocol, cotyledon and hypocotyl segments were grown on MS medium supplemented with 1.5 mg L⁻¹ 6-Benzylaminopurine (BA) and 0.2 mg L⁻¹ α-Naphthalene acetic acid (NAA), successfully induced callus and subsequently shoots for C. pepo L. cv. First Runner. The height percentage of shoot production frequency was 66.7% from 6 days old cotyledon explants in MS + 1.5 mg L⁻¹ BA + 0.2 mg L⁻¹ NAA combination. The shoot regener- ation frequency was increased up to 86.67% when 2.0 mg L⁻¹ AgNO₃ was added with MS + 1.5 mg L⁻¹ BA + 0.2 mg L⁻¹ NAA media combination by using 5 days old cotyledon explants. Shoot regeneration potentiality of four other C. pepo genotypes were also investigated with this system and showed a substantial amount of regeneration potentiality for different genotypes. Regenerated shoots induced the height 93.33% rooting frequency which pro- moted long, thick roots on 10 to 12 days in MS medium supplemented with 0.1 mg L⁻¹ NAA. The regenerated plantlets with long and thick roots were acclimatized in pot soil and eventually grown in natural environment with culture facility. The present study describes a simple and efficient protocol for in vitro plant regeneration of hybrid C. pepo genotypes and may be utilized for further transgenic development.