Algal biotechnology: real opportunities for Africa

The controlled and intense production of microalgae in photobioreactors has great potential for Africa. Of particular potential are; wastewater treatment, production of food and feed, production of bio-compounds, nutraceuticals and fine chemicals, and bioremediation. Microalgae have several competitive advantages over conventional crop production using agriculture and their biotechnology offers real economic potential. For the immediate future, products for the health food market and applications in bioremediation offer real opportunities for exploitation, environmental and economic benefits

Drought tolerance, traditional crops and biotechnology: breeding towards sustainable development

Germplasm of traditional vegetable crops were screened for drought tolerance. Different physiological, morphological and biochemical traits of drought tolerance were investigated, including enzymes of the antioxidative pathway (SOD, AP and GR), turgor maintenance (LWP, RWC), membrane stability (CMS, TTC), osmoprotection (proline), productivity (photosynthesis), rooting (root architecture), early drought tolerance and leaf area. Different in vitro screening techniques were carried out. Useful traits of drought tolerance were identified in Amaranthus tricolor, A. hybridus, A. hypochondriacus, Vigna unguiculata and V. subterranea, and are currently being applied in a breeding programme in an attempt to develop tolerant genotypes of neglected vegetable and seed crops that might contribute to secure food production in rural areas in Africa

Integrating biotechnology into the polyfarm concept

The polyfarm concept aims at strengthening traditional and appropriate farming technologies within the local agro-economic, cultural and socio-economic constraints of rural small farming. Different modules can be grouped together to suit the needs of the farmer. The polyfarm can serve as a demonstration and training facility to make rural farmers aware of the existence of biotechnologically-enhanced crops, their benefits and potential for use by resource-poor farmers. Enhanced soybean and maize are planted together with the conventional crop to demonstrate that these crops can improve yields, cut costs, reduce spraying and save time for the small-scale farmers

In vitro hardening — the role of supra-optimal sucrose on acclimation stress in Kniphofia leucocephala

Supra-optimal sucrose concentrations (6% and 9%) in vitro resulted in morphological and ultrastructural differences between control and stressed plantlets of Kniphofia leucocephala. Shoot length, in particular, was significantly reduced by increasing sucrose concentrations. Supra-optimal sucrose concentrations did not confer significant benefits on the stressed plantlets after transplanting, indicated by the similar maximum photochemical efficiency of photosystem A. However, environmental stresses ex vitro may not have been sufficiently great to elicit different responses from the control and stressed plantlets

Sustainable production of root and tuber crops (potato, sweet potato, indigenous potato, cassava) in southern Africa

Africa, including South Africa, is faced with a problem of increasing rural poverty that leads to increasing urbanisation, joblessness, crime, food insecurity and malnutrition. Root and tuber crops such as sweet potato and potato, as well as cassava and indigenous potato are important crops for food security. The latter are also important due to their tolerance to marginal conditions. Potato and sweet potato are of great economic value in South Africa, with well-organised marketing chains and, for potato, a large processing industry. There is one cassava starch extraction factory in operation in South Africa. A number of diseases are of importance in potato in South Africa: early blight, late blight, bacterial wilt, scab and virus. Insect pests such as tuber moth and leaf miner are also constraints. In sweet potato the occurrence of viruses and weevils, as well as the availability of healthy planting material are the most important limiting factors in production. African Cassava Mosaic Disease (CMD) caused by a virus, is a problem in growing cassava. Plant biotechnology applications offer a number of sustainable solutions. Basic applications such as in vitro genebanking where large numbers of accessions can be maintained in a small space, meristem cultures to produce virus-free plants and mass propagation of popular cultivars in order to make planting material available for sustainable production. More advanced biotechnology applications that may be of value are molecular marker technology and genetic engineering. The latter can play a role in overcoming virus and potato tuber moth in potato, in resistance to CMD in cassava and possibly in sweet potato to incorporate virus and weevil resistance

Ultrastructural observations on foliar glandular trichomes of Stevia rebaudiana

Foliar glandular trichomes of Stevia rebaudiana (Bert.) Bert. were examined by transmission electron microscopy in order to detect changes occurring in their cells in association with the secretory process. In the foliar, 10-celled lipophilic glandular trichome of Stevia rebaudiana (Bert.) Bert., the six secretory cells forming three pairs of head cells are vacuolated, possess large nuclei and are rich in ribosomes, mitochondria, plastids and ER elements. Dictyosomes are relatively frequent in these cells. The plastids, which form starch grains, are leucoplasts in cells of the apical pair and chloroplasts in cells of the two subapical pairs. The basal cells and stalk cells possess some degree of vacuolation and are rich in ribosomes. Also in these cells, the nuclei are relatively large; ER elements, chloroplasts and dictyosomes are present in moderate number, and mitochondria are frequent. Wall ingrowths are found in head cells as well as in the stalk and basal cells. Plasmodesmata, in moderate number, occur more frequently in transverse walls of head cells, as well as in those between cells of the second subapical pair and stalk cells and between the latter and basal cells. Plasmodesmata connect mesophyll cells and basal cells. To form the secretory sheath, the cuticular membrane detaches from the outer walls of the apical secretory cells, along a line that appears to be the pectin layer

Plant regeneration in vitro from immature embryos of lesser burnet (Sanguisorba minor Scop.)

Efficient and reproducible shoot regeneration has been established from immature zygotic embryos of lesser burnet on MS medium containing 4μM BAP and 10μM NAA. Regenerated shoots were best rooted in half-strength MS medium supplemented with 10μM NAA and later established in the greenhouse

Germ-furrow morphology and storage conditions determine the degree of viability of Pinus caribaea pollen

This study has found a correlation between Pinus caribaea pollen morphology and viability. Eighteen different P. caribaea pollen families were screened to determine the effect of environmental conditions during storage on germination. The results indicated that there was a direct decrease in viability with an increase in the age of the pollen, temperature at which the pollen was stored, and exposure to high humidity during storage. Scanning electron microscopy was used to investigate the dimensions of the 18 families. Upon statistical analysis of the dimensional data, the families were found to group into three clusters. Pollen families displaying narrow germ furrows clustered with those displaying wide germ furrows, while those pollen families displaying intermediate germ furrows clustered into a second group. When the clusters were compared with the germination data obtained it was found that the pollen families displaying highest germination percentages fell into the intermediate cluster, while the pollen families displaying low to intermediate germination percentages fell into the narrow/wide cluster

Watsonias as container plants: using paclobutrazol for flowering and height control

South African watsonias were evaluated for their potential as flowering pot plants, following chemical dwarfing. Corms were treated with paclobutrazol as a 5mg, 10mg or 20mg active ingredient (a.i.) per pot post-emergent soil drench, or vacuum-infiltrated pre-planting with 0.5mg, 1mg or 2mg a.i. per corm. Both treatments significantly reduced perpendicular leaf height, although infiltration of all but the most under-developed corms caused inflorescence abortion. Flowering plants shorter than 36cm were considered to be attractive, commercially viable pot plants — provided that flowering percentage, flower number and the onset of flowering were not adversely affected by treatment and that flowers were displayed clear of the foliage. The highest concentration of paclobutrazol applied as a drench resulted in obscured inflorescences, indicating an enhanced dwarfing effect on the inflorescence rather than leaf heights. Marketable dwarfs were obtained following a single drench treatment of 10mg a.i. per pot or after a single infiltration episode with 1mg a.i. per corm, allowing the successful adaptation of watsonias to container cultivation