| dc.description.abstract | Pigeon pea (Cajanus cajan (L) Millsp.) is an important multipurpose grain legume that
is a good source of protein for populations living in the semi-arid tropics. Being a crop
that is cultivated under rain-fed agricultural system, its production is threatened by
several biotic and abiotic stresses. Attempts to address these problems through
conventional breeding have achieved partial success due to narrow genetic variability
among the cultivated species. In addition, breeding incompatibility problems associated
with wild species warrant exploration of alternative approaches like gene transfer to
introduce desirable traits. Development of in vitro regeneration protocols amenable to
genetic transformation offer an attractive opportunity for improvement of pigeon pea.
Therefore the aim of this study was to develop a protocol for in vitro regeneration of
two pigeon pea (Cajanus cajan) varieties, KAT 60/8 and ICEAP 00557 grown in
Kenya. Murashige and Skoog (1962) (MS) basal media supplemented with various
auxin and cytokinin concentrations alone or in combinations and different explant types
(embryos or leaves) were tested for callus initiation, induction of somatic embryos,
shoot and root regeneration. For callus induction, MS medium supplemented with 0.5 –
4.0 mg/l 2, 4- dichlorophenoxyacetic acid (2, 4-D) and thidiazuron (TDZ) were tested.
For shoot and root regeneration, 0.1 mg/l and 0.5 mg/l 6- benzyl amino purine (BAP)
and 0.1- 1.0 mg/l Indole- 3- butyric acid (IBA) were tested respectively. Embryogenic
calli were obtained on MS medium with 2 mg/l TDZ and 1 mg/l 2, 4- D. Six week old
embryogenic calli were transferred to MS medium supplemented with 0.1 mg/l or 0.5
mg/l benzyl amino purine (BAP) or MS medium without hormones for shoot
regeneration. Regenerated shoots (>3 cm) were excised after approximately ten weeks
and transferred to MS medium with indole-3-butyric acid (IBA), for regeneration of
roots. Shoot regeneration (6.7%) was achieved with KAT 60/8 variety from leaf callus
induced on 1 mg/l 2, 4- D for 4 weeks and sub cultured on regeneration medium with
0.5 mg/l BAP for five weeks. No regenerants were obtained from ICEAP 00557 embryo
and leaf callus induced on 2, 4- D and sub cultured on regeneration medium with BAP.
The highest frequency of regeneration from ICEAP 00557 was achieved with leaf
explant on 0.5 mg/l TDZ giving 20.0%. On the other hand, a regeneration frequency of
16.67% was obtained with KAT 60/8 leaf explants on 2 mg/l TDZ. IBA at 0.5 mg/l
gave the most profuse rooting. Rooted shoots were hardened in a mixture of soil and
vermiculite (1:1) for 21 days after which they withered. From the results reported in this
study, the best explants for in vitro regeneration of pigeon pea varieties KAT 60/8 and
ICEAP 00557 are leaf discs.
The results obtained show that genotype, plant growth regulator and explant type have a
great influence on the success of an in vitro regeneration system. Moreover,
optimization of the protocols generated in this study will step up the prospects for mass
production of pigeon pea and genetic manipulation. | en_US |
