Download Abstract

SP09-01
Production of, and regeneration of friable embryogenic callus and
Apical shoot tips in Ugandan farmer-preferred cassava genotypes
Hellen B. Apio1,2*,Wagaba Henry1, Titus Alicai1, Yona Baguma1, Settumba B. Mukasa2, Anton
Bua1 and Nigel Taylor3
1) NaCRRI, K’la, Ug, 2) CAES, MUK, K’la, Ug, 3)DDPSC, 975 NWR, MO, USA
*[email protected], Registrant ID# 4714
Production of embryogenic callus is a key step in genetic engineering of many crop species,
including cassava. Protocols for generation of friable embryogenic callus (FEC) and regeneration
of apical shoot tips have been lacking for Ugandan cassava genotypes, thereby delaying their
genetic engineering for agronomic and other desirable traits. The objective of this study was to
determine conditions suitable for production of FEC, regeneration of plants for cultivars Aladu,
Bukalasa, Ebwanatereka and the model variety 60444. In addition, regeneration of plants from
apical shoot tips of TME 204, Bukalasa, Nase 3, Nase 12, Nase 13, Nase 14 and Nam 130 was
attempted. Immature leaf explants were established on Murashige and Skoog (MS) based
media for initiation of organized embryogenic structures (OES). To produce FEC, the resulting
OES was subcultured onto Gresshoff and Doy based media supplemented with varying levels of
sucrose, maltose, tyrosine, tryptophan, naphthalene acetic acid (NAA) under light and dark
conditions. Subsequently, FEC was subcultured to MS-based embryo maturation and embryo
regeneration media. Apical shoots tips, 3MM in size were established on MS media
supplemented with benzylaminopurine (BAP) for shoot proliferation before transfer to MS
supplemented with naphthalene acetic acid (NAA) for root formation. All genotypes produced
OES and all genotypes produced FEC except Bukalasa. The amino acid tyrosine favoured
production of FEC in Aladu and Ebwanatereka, but not in 60444. while 20 g/L of Sucrose at 20
g/l triggered production of FEC in Aladu and 60444, but 40 g/L of sucrose was superior for
Ebwanatereka. Media supplemented with 1µM NAA facilitated somatic embryo regeneration in
Ebwanatereka and 60444, while Aladu responded better to 5µM NAA. Light, tyrosine and
sucrose were essential for FEC production in Uganda cultivars while NAA was required for
regeneration of somatic embryos. Apical shoot tips from all the genotypes regenerated plants.
The cytokinin BAP at 1 µM favoured regeneration of meristematic tips in genotypes Nase 3,
Nase 12, Nase 13 and Nam 130 while TME 204, Nase 14 and Bukalasa responded better at
0.5µM BAP. Complete regeneration of apical shoot tips was possible at 1µM NAA for all
genotypes derived from apical shoot tips while 1µM BAP was essential for plants regenerated
from FEC. The ability of apical shoot tips and FEC from these genotypes to regenerate into
plants, lays a foundation for their improvement through genetic transformation for the desired
and agronomic traits.
Keywords: Cassava, Friable embryogenic callus, Meristematic tips, Amino acids, Carbon
sources, Plant growth regulators