In vitro rapid regeneration through direct organogenesis and ex-vitro establishment of Cucumis trigonus Roxb.—An underutilized pharmaceutically important cucurbit

• Cucumis trigonus is promising candidate to fulfill the demands of pharmaceutical and nutraceutical industries.
• Simple, rapid, reproducible and cost-effective approach for regeneration of elite, genetically homogenous germplasm.
• Direct organogenesis using axenic nodal explants, leads to low risk of somaclonal variations.
• An efficient alternative system for commercial cultivation and extraction of active biomolecules.
• The established protocol useful for the conservation of other rare and endemic Cucumis spp.

Rapid, reproducible and prolific in vitro plant regeneration via direct organogenesis has been achieved from axenic seedling derived nodal explants of Cucumis trigonus Roxb.—an underexploited plant of an immense industrial value in coming years. The organogenic capability of nodal segments was investigated on Murashige and Skoog (MS) medium supplemented with different concentrations of cytokinins and auxins either alone or in combinations. The highest frequency of shoot induction (92.00 ± 1.73) was achieved when nodal explants were cultured on Murashige and Skoog (MS) medium incorporated with 2.0 mg/l 6-benzylaminopurine (BAP) with an average of (4.90 ± 0.25) shoots per node explant. Microshoots exhibited best rooting response on ½ strength MS medium supplemented with 1.0 mg/l indole-3-butyric acid (IBA) by producing a highest frequency of root formation (100%), number of roots (21.6 ± 0.88) and root length (7.00 ± 0.73 cm) were achieved after four weeks. The rooted microshoots were successfully hardened and transplanted from different planting substrates to the field with maximum survival rate (95%). Micropropagated plants established ex-vitro was uniform and identical to donor plants with respect to vegetative and reproductive phase of growth. The present cost-effective regeneration protocol would facilitate an alternative method for fast mass multiplication of Cucumis trigonus to fulfil the pharmaceutical and nutraceutical needs of growing population. This the first report of an efficient in vitro regeneration protocol for C. trigonus through direct organogenesis via axenic seedling derived nodal explants, which can be efficiently applied for the exploitation of active biomolecules, genetic manipulations of commercially valuable genotypes of Cucumis and also helps to speed up cucurbit breeding programmes.

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