MOLECULAR GENETIC DIVERSITY AND EFFICIENT PLANT REGENERATION SYSTEM VIA SOMATIC EMBRYOGENESIS IN SWEET POTATO (Ipomoea batatas (L.) Lam.)

Abstract

Somatic embryogenesis and plant regeneration at high frequency have been restricted to few sweet potato varieties. For enhancing and accelerating somatic embryogenesis from stem segments of the Egyptian sweet potato cultivar Abees were investigated using three different phytohormones; 2,4-dichlorophenoxy-acetic acid (2,4-D), benzyleaminopurine (BAP) and indole acetic acid (IAA). The phytohormone BAP was found to be the best for the induction of embryogenic calli and most studied traits. Data analysis showed a significant variation in three different tissue culture media for all parameters, expect root induction percentage. Two different isozymes; peroxidase (PRX) and α naphthyl acetate esterase (EST) were used and analyzed to determine the genetic variability among the regenerated plants. The two analyzed isozymes successively showed polymorphic variations among the parent and 98 sweet potato plants regenerated from the three different callus induction media. Peroxidase isozyme produced seven polymorphic bands showing genetic variation as compared to the control (Abees cultivar), while esterase isozyme produced only three polymorphic bands. The regenerated plants exhibited somaclonal variations that can be utilized for selection of desired traits in sweet potato. On the other hand, five RAPD primers were used for assessment of genetic diversity in the somaclonal variants compared with control. A total of 68 RAPD loci were amplified with molecular size range of 300–3000 bp with 13.6 loci per each primer. Out of the 68 loci scored, 26 loci (38.24%) were found to be polymorphic and the polymorphism% ranged between 18.18% for (OPB-05) and 75% for (OPB-07). Moreover, all primers produced positive and negative unique DNA bands, except OPB-05 for negative unique bands and OPB-07 for positive unique bands. The same result was confirmed by the cluster and principal coordinate analyses for the positions of somaclonal variant no. 4 which showed high diversity from the parental cultivar.