Abstract
A procedure to regenerate cassava (Manihot esculenta Crantz) cultivars from Cameroon via somatic embryogenesis (SE) was developed. Shoot apical meristems and immature leaf lobes were used as explants on Murashige and Skoog (MS) basal medium containing 33 or 50 µM of the auxins Picloram (Pic), 2,4-Dichlorophenoxyacetic acid (2,4-D), Dicamba (Dic), and α-Naphthalene acetic acid. Cultivar performance was assessed using SE and number of somatic embryos produced. Overall, the frequency of primary somatic embryogenesis (PSE) and the mean number of somatic embryos produced varied considerably with genotype, type of auxin and concentration tested. For example, cultivar (cv.) Ngan Mbada showed the best performance on MS medium supplemented with 50 µM Pic with a SE frequency of 40 % and an average number of somatic embryos of 90. The second best performance was recorded in cv. Local Red on MS medium supplemented with 33 µM 2,4-D, where the SE frequency was 40 % and an average number of somatic embryos of 60.5. Cultivar Ekona Red recorded the best performance on medium supplemented with 50 µM Pic showing a SE frequency of 47 % and an average number of somatic embryos of 45. We further examined secondary and cyclic somatic embryogenesis (SSE, CSE) and both were also observed to vary with genotype, however, both exhibited significantly higher frequencies of SE compared with PSE. SE started to decline at the fourth cycle of embryogenesis. Examination of organogenesis showed that shoot bud induction from green cotyledons varied across cultivars and benzylaminopurine was shown to outperform Thidiazuron in the ability to induce organogenesis. Furthermore, the frequencies of bud induction were identical under light and dark conditions. Finally, regenerated plants grew easily in the greenhouse with 90–100 % survival rate and did not display detectable variation in morphology.
Highlights
Cassava (Manihot esculenta Crantz) is a staple food to nearly a billion people in about 105 countries, providing as much as a third of daily calorie intake (FAO 2008a, b)
Effect of plant growth regulators on induction of primary somatic embryogenesis In this study, seven cassava cultivars from Cameroon were tested for their ability to induce primary somatic embryos on Murashige and Skoog (MS) basal medium containing two concentrations (33 and 50 μM) of 2,4-D, Pic, Naphthalene acetic acid (NAA) and Dic
We showed that the frequency of somatic embryogenesis and the number of embryos produced per explant varied with cultivar and auxin, suggesting a genotype-auxin interaction effect as reported by others (Feitosa et al 2007; Saelim et al 2006; Rossin and Rey 2011)
Summary
Cassava (Manihot esculenta Crantz) is a staple food to nearly a billion people in about 105 countries, providing as much as a third of daily calorie intake (FAO 2008a, b). Because of its resilience and Despite its potentials for achieving food security and economic growth, biotic and abiotic constraints such as diseases, pests, weeds, and drought are limiting cassava production (Barceloux 2009; Bull et al 2011). In addition to these constraints, production has several other constraints, including toxic cyanogenic compounds, very low protein content (1–2 % dried weight) and short fresh. Important traits have been introgressed through traditional breeding, leading to major improvements in resistance to bacterial blight and viruses (Okogbenin et al 2007). Cassava genetic transformation has emerged as a valuable alternative and complementary approach to improve the crop (Sayre et al 2011; Liu et al 2011)
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