In vitro Regeneration of Wild species of Guar (Cyamopsis serrata and Cyamopsis senegalensis)

Wild relatives of Cyamopsis i.e. C. serrata is an early maturing (40–50 days), slow growing and branched species, while the other species i.e. C. senegalensis is a slow growing annual herb and matures in 120–130 days. Both these wild relatives possess some desirable attributes like drought resistance, photo-and thermo-insensitivity and disease resistance.

Seedling explants like cotyledon, cotyledonary node and hypocotyl taken from 7–10 d old aseptically grown seedlings and immature embryos (10–12 d after pollination) were cultured on MS medium with B5 vitamins and fortified with different concentrations of growth regulators. Maximum callus induction from cotyledon explant was evident in C. serrata and C. senegalensis on MS medium with B5 vitamins and supplemented 2, 4-D (2mg/l). Hypocotyl explants of both the tested species of Cyamopsis showed very good callus induction response in media supplemented with 2, 4-D @2mg/l. BAP at concentrations of 0.5 and 2.0 mg/l supported indirect multiple shoot regeneration via callusing in C. senegalensis whereas 1 mg/l BAP supported direct multiple shoot regeneration. On the other hand, BAP induced differentiation of multiple shoots in C. serrata and the number of shoots per hypocotyl explant increased with the increasing concentration of BAP. Indirect shoot regeneration from hypocotyl explants was evident in C. serrata at MS medium supplemented with 1mg/l each of NAA and BAP, whereas NAA (2mg/l) with BAP(1mg/l) and NAA(2mg/l) with BAP(2mg/l) showed callusing in both the wild species. Cotyledonary node explant was the most responsive explant for plant regeneration in both the wild species of Cyamopsis under investigation. Indirect shoot regeneration in C. serrata was observed in MS medium supplemented with NAA alone and response increased at 2mg/l. NAA induced only callusing from cotyledonary nodes in C. senegalensis. 2,4-D (1mg/l) induced callusing and indirect shoot regeneration in C. serrata and C. senegalensis while its higher dose (2mg/l) induced callusing only from cotyledonary node explant in both the species tested. Supplementation of MS medium with BAP alone lead to indirect shoot regeneration via callusing and its frequency decreased with increasing its concentration for 0.5 mg/l to 2.0 mg/l. Interestingly, 2mg/l BAP supported multiple shoot formation from cotyledonary explants in C. serrata. Supplementation of 1.0 mg/l BAP to the medium containing 2.0 mg/l NAA lead to indirect shoot regeneration in C. senegalensis while it induced only callusing in C. serrata. The frequency of shoot regeneration however, decreased with the increase in concentration of BAP to 2mg/l. Half strength of MS with 0.1 mg/l and 0.5 mg/l IBA supported best rooting in C. senegalensis and C. serrata, respectively and plantlets were successfully transferred to paper cups.