Somatic embryogenesis from nucellar callus of cashew.

Abstract

SummaryCalli were initiated from bisected ovules with intact nucelli from 3 week-old immature cashew nuts (Anacardium occidentale L. cvs. ‘NRCC Sel-2’, ‘Ullal-1’, ‘Ullal-3’, ‘Goa 11/6’, ‘Vengurla-8’ and ‘Kanaka’) cultured on half-strength Murashige and Skoog (1962) medium (MS) containing 2,4-dichlorophenoxy-acetic acid (2,4-D; at 1.0 or 4.0 µM) alone, or a combination of 2,4-D (0.5, 1.0 or 4.0 µM) with 12 µM kinetin or 10 µM spermine. Calli, which became brown after 4–6 weeks, differentiated into somatic embryos on Raj Bhansali medium (RBM) containing 2,4-D (0.01 or 0.5 µM) and 30 µM kinetin or 10 µM spermine. Somatic embryos were initiated in 2.2 – 27.7% of cultures of cultivars ‘Goa 11/6’, ‘Kanaka’ and ‘Ullal-3’ only. The number of somatic embryos increased more than 5-fold following suspension culture in RBM basal medium. Histological studies on nucellar calli revealed differentiation of all the developmental stages of somatic embryogenesis: a pro-embryonic mass, and globular and heart-shaped embryos. Somatic embryos matured on half-strength MS medium containing 18.9 µM abscisic acid, and 60% germinated on liquid medium containing 0.53 µM -naphthalene acetic acid (NAA) and 4.4 µM 6-benzylamino purine (BAP) giving plantlets with a well-developed tap-root and a shoot with rudimentary green leaves.