| dc.description.abstract | Wheat (Triticum aestivum L.) is the second most important food crop in Kenya by production
and consumption, after maize. However, national wheat productivity has been on the decline
due to its vulnerability to a number of biotic and abiotic stresses. Tissue culture can be
exploited for improvement of this crop for better yields and other desired attributes including
superior grain quality. Due to the fact that tissues culture is highly dependent on genotype
and explant type, this study was done to establish a regeneration system for two Kenyan
wheat cultivars (Njoro BW II and Eagle 10) using mature seed embryo explants.
Three disinfectants Jik® (3.85% w/v NaClO), 0.1% w/v mercuric chloride and chlorine gas
were investigated for their effectiveness in establishment of axenic cultures. Murashige and
Skoog (MS) medium with 0.5-8mg/l of 2, 4-dichlorophenoxyacetic acid (2, 4-D), 1naphthaleneacetic
acid (NAA) and 4-chlorophenoxyacetic acid (4-CPA) were tested for
callus induction. After 7-14 days of initial callus induction, calli obtained were sub-cultured
to fresh MS medium of the same composition for proliferation. After 30 days, calli were subcultured
to hormone free MS medium or MS medium supplemented with 6benzylaminopurine
(BAP), kinetin (KN) and thidiazuron (TDZ) at 0.25-2 mg/l alone or in
combination with 0.1 mg/l indole acetic acid (IAA) for in vitro shoot or plantlet regeneration.
The plantlets obtained were acclimatized using sterile vermiculite for 14 days followed by
vermiculite with soil (1:1) in the culture room for 14 days and eventually unsterile soil alone
in the green house. Data on percentage callus induction, callus fresh weight and regeneration
were subjected to one way analysis of variance (ANOVA) and means separated by Tukey’s
HSD test at p ≤ 0.05.
All the auxins 4-CPA, NAA and 2, 4-D tested were able to induce callus in 20-90% of mature
seed embryos in both cultivars within 1-4 days. However, 2, 4-D induced higher frequencies of callus than 4-CPA or NAA at all concentrations used. Combining 2 mg/l 2, 4-D with either
0.2 mg/l NAA or 4-CPA produced up to 13% higher frequency of callus induction in both
cultivars than when 2, 4-D was used alone. Somatic embryogenesis was observed in calli
inoculated in medium with 1-8 mg/l 2, 4-D. The highest embryogenic callus induction
frequency (i.e. 63%) was observed in MS medium containing 2 mg/l 2, 4-D in combination
with 0.2 mg/l 4-CPA. Plant regeneration was achieved after 12-24 days on MS hormone free
medium. The highest plant regeneration frequency of 67% was achieved on medium
containing 0.5 mg/l BAP plus 0.1 mg/l IAA. A total 9% of plantlets acclimatized survived to
maturity. It took 90-100 days from callus initiation to plantlet establishment.
This study shows that mature seed embryos can be used to regenerate fertile wheat plantlets.
The findings have the potential to inform future effort in the application of tissue culture for
expedited wheat cultivar improvement in Kenya.
Key words:
Triticum aestivum, mature seed embryos, somatic embryogenesis | en_US |
