In vitro conservation of pointed gourd (Trichosanthes dioica) germplasm through slow-growth shoot cultures: Effect of flurprimidol and triiodobenzoic acid

• Flurprimidol in the medium suppressed shoot growth of pointed gourd cultures, but it promoted leaf (up to 5.0 μM) and root development.
• Shoot explants cultured on MS medium with 7.5 μM flurprimidol when stored at 9 °C survived for 784 days.
• Triiodobenzoic acid (TIBA) at low concentrations (10−8 M) promoted shoot growth and number of leaves per culture, but at higher concentrations it had suppressive effect, and the shoot cultures survived for 280 days.
• Pointed gourd cultures grown on GR-free MS medium and stored at 9 °C survived ∼700 days; which could be preferable to the 7.5 μM flurprimidol, but if low temperature storage is not feasible, the cultures may be maintained on MS medium with 7.5 μM flurprimidol at 25 °C.

The effects of growth retardants, flurprimidol and triiodobenzoic acid (TIBA) were investigated on the development of slow-growth cultures aimed for in vitro conservation of pointed gourd (Trichosanthes dioica) germplasm. Shoot cultures maintained on MS medium supplemented with flurprimidol (1.0, 2.0, 5.0, 7.5, 8.8, 10.0, 12.5, 15.0, 20.0 μM) or TIBA (10−3, 10−4, 10−5, 10−6, 10−7, 10−8 M) were stored at 25 °C and 9 °C. In general, flurprimidol in the medium suppressed shoot growth, but it promoted leaf (up to 5.0 μM) and root development (all the tested concentrations). The optimum concentration of flurprimidol for storage of the cultures was 7.5 μM as it supported culture survival for 784 days, when stored at 9 °C. In general, TIBA promoted shoot growth and number of leaves per culture at low concentrations (10−8 M), but it had suppressive effect at the higher concentrations. However, root number per culture decreased significantly in response to even 10−8 M TIBA. The shoot cultures maintained on medium containing 10−8 M TIBA survived for 280 d, while the cultures grown on GR-free MS medium and stored at 9 °C survived much longer (∼700 d). Use of TIBA for slow-growth of pointed gourd shoot cultures did not offered any advantage over the GR-free MS medium. The cultures stored at 9 °C survived much longer than those stored at 25 °C. The GR-free MS medium may be preferable to the 7.5 μM fluprimidol as it supported culture survival for up to 700 d at 9 °C, and avoids the additional cost and the possible undesirable physiological and genetic effects of the growth retardant. But when low temperature storage is not feasible, the cultures may be maintained on MS medium supplemented with flurprimidol (5.0 or 7.5 μM) as the cultures survived up to 364 d at 25 °C.