ABSTRACT
35S promoter from the Cauliflower Mosaic Virus (pCaMV) is a constitutive promoter commonly used in plant genetic transformation while Cassava Mosaic Virus (pCsVMV) is another promoter which is underutilized. The combination of the two promoters was used to form (pOYE153). The method adopted includes the insertion of a β–glucuronidase reporter gene (UidA) into a promoter cassette comprising the CsVMV promoter. The second construct (pCAMBIA2310) had (pCaMV) used for the selectable marker and gene of interest. This construct was mobilized into Agrobacterium tumefaciens strain LBA4404 and then tested for expression of the UidA gene in transient assays in cassava somatic embryos. After co-cultivation of these Agrobacterium with the plant tissues, histochemical β–glucuronidase (GUS) assays were performed to determine the level of UidA gene expression in transient assays. The results showed that the pCsVMV was able to drive high gene expression of β–glucuronidase reporter gene (UidA) in the transient assays in cassava somatic embryo. Expression of the gene also increases with the increase in the day of cocultivation and likewise expression of the gene was higher for the sample in the light than the dark.
ABSTRACT
This study investigated the influence of age of the cotyledons, cut from primary somatic embryos (PSE) developed from shoot meristems (SM) or immature leaf lobes (LL), on secondary somatic (SSE) and cyclic (CSE) embryogenesis of two cassava cultivars at the Central Biotech Laboratory, International Institute of Tropical Agriculture (IITA), Ibadan, between 2006 and 2010. A completely randomized design with three replicates was used for the study. Only PSE at the age of 4 weeks recorded significant (P<0.05) differences in SSE frequency and efficiency between the SM and LL sources. CSE production was highest using 0 to 4 weeks old SSE cotyledons, and significant (P<0.05) differences were only recorded between the SM and LL sources when the age of the SSE cotyledons was older than 6 weeks. The CSE frequencies from the SM source were significantly greater than that from the LL source when 8 and 10 week-old SSE cotyledons were used. The CSE frequencies from SM (81%, 82%) were still significantly higher than those from LL (41%, 40%) at the 5th and 6th cycles respectively while the CSE efficiency only differed at the 4th cycle, with SM (7.1) being significantly more than from LL (5.2). These results also enrich the literature by specifying the age of somatic cotyledon suitable for further somatic embryogenic cycles; 0 to 8 weeks for SSE and 0 to 5 weeks for CSE, irrespective of the cultivar (TME 12 or Kibaha) or source (SM or LL). This study further concluded that cyclic embryos should be discarded after the 4th CSE cycle and fresh starting material should be used to restart the somatic embryogenic process.
ABSTRACT
The study evaluated high-value African cassava varieties for primary somatic embryogenesis using axillary meristems (AM) and immature leaf lobes (LL) on piclorambased medium. The study was conducted at the Central Biotech Lab, International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria between 2006 and 2009. Completely randomized design with four replicates was used for the study. Using LL explants, there were significant (P=.05) differences in percent responding leaf lobes, percent explant with pre-embryogenic structure, PSEF and PSEE among cassava varieties. The PSEF of the only three varieties that produced mature somatic embryo were 93.6, 88.5 and 85.7% for TME 12, Kibaha and Albert, respectively. Similarly, significant (P=.05) differences existed among the varieties in percent enlarged axillary meristem, percent explant with pre-embryogenic structure, PSEF and PSEE when AM was the explant. The PSEFs of the only three varieties that produced mature somatic embryo were 83.6, 77.5 and 72.7% for TME 12, Kibaha and Albert, respectively. The PSEF and PSEE of LL explant were greater than those of AM by an average of 86.1% and 82.7%, respectively. The study concluded that both AM and LL were good explants for production of primary somatic embryo in cassava.