Benzyladenine-induced adventitious shoot regeneration from hypocotyls of adzukibean (Vigna angularis {Willd.} Ohwi & Ohashi)

A complete in vitro plant regeneration systemvia adventitious shoot-bud formation from seedlinghypocotyls of adzukibean was developed. Cotyledonarynode (CN) and root explants from 4-d-old invitro-germinated seedlings of 4 cultivars werecultured on agar-solidified R medium consisting of MSsalts, B5 vitamins, 3.0% (w/v) sucrose and 4.4 µM6-benzyladenine (BA). Shoot buds arose adventitiouslyat the basipetal cut of the hypocotyl in 40 to 85%of type 1 CN (8–10 mm) explants 6 weeks later with cvsBansei aki azuki and Tanbadainagon azuki exhibitingsignificantly higher response. Shorter type 2 (4–5 mm) CN explants responded poorly (0–6%) in culturewhile intact roots were regenerative but at lowerfrequencies (5 to 31%). In cv Bansei aki azuki,optimum shoot initiation (78.7%) was achieved whentype 1 CN explants from BA-preconditioned seedlingswere re-cultured in R medium (SC0). BA supplied at8.8 µM during SC0 significantly reduced the shootinitiation response to 46.7%. In the same manner,substituting equimolar concentration (4.4 µM) ofkinetin (KN), zeatin (Z) or thidiazuron (TDZ) to BAduring SC0 yielded no or significantly lowerresponses. Mean shoot production ranged from 6.2 to9.8 shoots per explant 6 weeks after subculture (SC1)and varied significantly among the 4 cultivars used. Efficient rooting (93–96%) was achieved on excisedshoots transferred to MS salts + B5 vitamins basalmedium alone. The tissue culture system covered only16 weeks to completion. Regenerated plantlets weretransferred to soil with 86–100% survival rate andall surviving plants were morphologically normal andseed-fertile.