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The primary gene pool (GP-1) of a crop is composed of gene reservoirs that cross easily with the domesticated, while the crosses regularly produce fertile offspring. The GP-1 is further subdivided into cultivated and wild gene pools. The cultivated gene pool encompasses commercial stocks of the crop, as well as landraces. The wild GP-1 of the crop comprises putative ancestors and closely related species...
The procedures required to produce genetically transformed cassava were developed and are now in place in three laboratories in the USA and Europe. Future implementation and sustainability of transgenic technologies for the agronomic improvement of cassava will depend, however, on transferring these capabilities to locations where cassava has an important socioeconomic niche. If successful, such countries...
The aim of this study was to examine the embryogenic potential of floral material of the cassava cultivar MCOL 1505. Macerated immature inflorescences were found to be highly embryogenic, with almost 78% of the explants producing somatic embryos. Somatic embryos were also produced from whole male florets and half florets although at much lower rates. No regeneration was obtained from anther, microspore...
Knowledge of the origin, organization and nature of the cassava (Manihot esculenta Crantz) germplasm collection in Brazil is incomplete due to lack of critical information on several aspects of the collection. This study verifies the utility of SSR-primed PCR markers for germplasm assessment and then utilizes these markers as well as RAPD's to characterize the Brazilian collection. We specifically...
The storage roots of cassava (Manihot esculenta Crantz) suffer from a rapid post-harvest deterioration that is a major constraint to their increased exploitation. In many ways this deterioration resembles wound responses in other better studied plant systems, though it appears to lack an adequate wound repair response. A cDNA clone (cMeHRGP1) for a hydroxyproline-rich glycoprotein expressed during...
Screening of a tuber specific cassava cDNA library resulted in the isolation of full length cDNA clones with homology to the genes encoding the small and large subunits of ADP glucose pyrophosphoryalse. Sequence analysis revealed that AGPase B the clone with homology to the small subunit shared 54% homology at amino acid level with the AGPase S clone that is more closely related to the large subunit...
Cassava bacterial blight (CBB), caused by Xanthomonas axonopodis pv. manihotis (Xam), is a particularly destructive disease in South America and Africa. The movement of infected asymptomatic stems is a major means of pathogen dispersal as well as infected seeds. The success of a cassava-seed certification program depends on the availability of reliable tests to detect the pathogen in vegetative planting...
A protocol was established for high frequency cyclic somatic embryogenesis for different varieties of cassava. An efficient plant regeneration system was developed for the high cyanogenic variety PRC60a. Linamarin content and linamarase activity were determined in various tissues of secondary somatic embryos and regenerated plants of PRC 60a. Both linamarin and linamarase activity were not detected...
In this paper we present original data on morphological and genetic diversity of cassava managed by the Makushi Amerindians from Guyana. Although they propagate cassava exclusively vegetatively by means of stem cuttings, many Amerindian farmers also use and multiply volunteer plants grown from seeds produced by sexual reproduction. Morphological characters were recorded for 29 varieties cultivated...
In order to isolate an elongation factor-1α (EF-1α)gene from cassava, a lambda EMBL3 genomic library, made from a single cassava genotype (MBRA 534, from the CIAT cassava germplasm collection), was screened with a full length EF-1α cDNA clone(blt63) from barley. Six positive clones were isolated from an amplified library and 4866 bp from one clone (MeEF1) were subcloned into pGEM3zf(-) and pGEM5zf(-)...
One of the major problems for cassava is the rapid deterioration after harvesting cassava tuberous roots, which limits the possibilities for production and distribution of cassava in the world. Postharvest deterioration is an inherent problem for cassava since wounding and mechanical damage of the tuberous roots cannot be prevented during harvesting, which includes postharvest physiological deterioration...
Breeding goals of yield increases, root quality improvement, and disease resistance in cassava are considerably slowed down by biological characteristics of the crop, which includes a long growth cycle, a heterozygous genetic background and a poor knowledge of the organization of crop diversity. These factors severely hamper the speed and ease of moving around useful genes in cassava. The consequences...
An efficient and reproducible method was developed for Agrobacterium-mediated transformation of embryogenic suspension cultures of cassava. LBA4404(pTOK233), containing the nptII, hph and gus marker genes, was used in the experiments. Chemical selection by means of kanamycin was used to establish 1037antibiotic resistant callus lines, of which 526 showed GUS expression. Of the 241 callus lines that...
The virological situation of cassava in Africa is increasing in complexity due to the number and types of viruses isolated from different locations within the continent. Here, we report the complete nucleotide sequences of both A and B components of two geminivirus species infecting cassava in the Ivory Coast and review the current knowledge of the molecular and biological diversity of the African...
Cassava has the reputation of being a drought tolerant crop, however, when deprived of water, plant and root development are affected. This ultimately will translate to an altered starch synthesis expressed by variation of starch quality. The magnitude of which, is influenced by the severity of stress conditions and stage of plant maturity. During early plant development,water stress retards growth,...
Disorganised embryogenic tissues have been utilised as target tissues for transgene insertion and transgenic plant regeneration in cassava (Manihot esculenta). The production of friable embryogenic callus in fourteen geographically diverse cassava cultivars, from which eleven were established as embryogenic suspension cultures, is reported. Embryogenic tissues were similar in nature in all cultivars...
In cassava friable embryogenic callus (FEC) has been used to obtain transgenic plants using particle bombardment, electroporation, and Agrobacterium tumefaciens. FEC cultures have been obtained in 6 of the10 tested genotypes. In all genotypes FEC could be regenerated into plants,however the efficiency differed between the genotypes. Almost all plants regenerated from 6 months old FEC cultures of TMS604444,...
The aim of this study was to obtain information on the response of cassava(Manihot esculenta Crantz) to root-knot nematode infestation. To achieve this aim, a novel in vitro dual root/nematode culture method was used, where root cultures of several cassava cultivars were inoculated with axenic Meloidogyne javanica eggs. Following an incubation period,cassava roots were stained, weighed and dissected...
Tomato mosaic virus (ToMV) is a limiting factor for the success of pepino (Solarium muricatum) as a new crop. The effects of ToMV infection on total and marketable yield, fruit weight, length/width ratio and soluble solids content (SSC) have been studied in two commercial clones (`Sweet Long' and `Sweet Round'). ToMV infection depressed total yield in infected plants of `Sweet Long' (43.1%), while...
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