Elsa S. du Toit

Plant regeneration through somatic embryogenesis of jacket plum (Pappea capensis)

Abstract The study was undertaken to identify an effective culture growing system for mass multiplication of jacket plum (Pappea capensis) through somatic embryogenesis. Calli derived from leaf sections were transferred onto Murashige and Skoog (MS) medium with different supplements. The most effective medium for callus induction was MS supplemented with 0.1 mg litre−1 thidiazuron (TDZ) alone or with 0.1 mg litre−1 indole‐3‐butyric acid (IBA) or a combination of 1.0 mg litre−1 2,4‐dichlorophenoxyacetic acid (2,4‐D) and 0.2 mg litre−1 benzylaminopurine (BAP). Light exposure promoted embryo induction. Three‐quarter strength MS medium supplemented with 0.05 mg litre−1 TDZ and 0.3 mg litre−1 casein hydrolysate (CH) was effective for embryo germination and the most effective culture medium for plantlet conversion was three‐quarter strength MS supplemented with 0.2 mg litre−1 BAP and 0.3 mg litre−1 CH. There was 60% survival of plants under a mist propagation chamber. The study shows that it is possible to improve P. capensis somatic embryogenesis through manipulation of some culture medium constituents and incubation conditions.

Germination and ultrastructural studies of seeds produced by a fast-growing, drought-resistant tree: implications for its domestication and seed storage

The inner layers of the seed coat that remain attached to the cotyledons probably play a role in seed dormancy of Moringa oleifera. Cotyledons of seeds stored for one year showed no sign of deterioration. In some cells of the three-year-old cotyledons, the membranes of the protein bodies were deteriorated. Cell deterioration was also marked by the collapse of the cell wall adjacent to the intercellular cavity. The decrease in seed viability during storage is associated with the loss in membrane integrity as confirmed by the increase in electrolyte leakage. The longevity of seeds can be extended if they are stored within their fruits under favourable conditions.

Origin of the Coleorhiza in Cycad Seedlings and its Structural Homology with That of the Poaceae

In the literature there is disagreement about the existence of a coleorhiza in cycad embryos. In this paper the terminology of the cycad ovule, seed and embryo is revised. It was confirmed that the cycad ovule and seed are pachychalazal and that the seed coat is exclusively formed by the pachychalaza. The term ‘pleurotesta’ as a substitute for the so-called ‘endotesta’ is suggested to describe the inner, membranous part of the seed coat. The anatomy of the cycad embryo was studied in comparison with the grass embryo and it was found that a coleorhiza does exist in cycad embryos and derives from the distal part of the suspensor. It is postulated that the coleorhiza in grasses also derives from the distal part of the suspensor and that the two structures are therefore structurally homologous.ZusammenfassungIn der Literatur gibt es Unstimmigkeit über die Existenz einer Coleorhiza in Palmfarn-Embryonen. In diesem Dokument werden die Termen der Palmfarne Samenanlage, Saatgut und Embryo überarbeitet. Es wurde bestätigt, dass die Palmfarnen-Samenanlage und Saatgut Pachychalazal sind, und dass das Saatgut-Fell ausschließlich durch das Pachychalaza gebildet wird. Der Begriff * Pleurotesta * wird also als Ersatz für die so-genannten * Endotesta * vorgeschlagen, den inneren, Membranöse Teil des Saatgut-Fells zu beschreiben. Die Anatomie der Palmfarn-Embryos wurde untersucht, im Vergleich zu Gras Embryonen und es wurde gefunden, dass eine Coleorhiza in Palmfarn-Embryonen vorhanden ist und stammt von dem distalen Teil des Suspensors. Es wird postuliert, dass die Coleorhiza in Gräser auch abgeleitet ist aus dem distalen Teil des Suspensors und das beide Strukturen daher struktur-gemäss homolog sein.

Efficacy and Utilization of Fungicides and Other Antibiotics for Aseptic Plant Cultures

In vitro plant culture which encompasses cell, tissue, organ and also embryo culture has been a vital technique for mass multiplication of plants (propagules), elimination of plant diseases thorough meristematic tissue culture technique, plant conservation (through cryopreservation) and crop improvement through gene transfer (Pierik, 1987; George, 1993; Singh & Chand, 2003; Sarasan et al., 2011). In vitro culture techniques have been used to shorten breeding cycles of plants and to achieve genetic transformation (Singh & Chand, 2003). Despite the several merits of in vitro culture techniques to the modern world where plant diseases, flower/fruit abortions and low plant regeneration capacity are major challenges, many developing countries, especially in Africa do not utilize them to address the numerous challenges in crop production and improvements. This is mainly due to the high investment costs in equipment, chemicals and intensive and skilled labor demands (Sarasan et al., 2011).

Effect of moringa extract on the leaf anatomy and yield potential of tomato infected by Alternaria solani

Tomato is often exposed to hormones and diseases, among other factors, to which responses in leaf anatomy and yield are observed. This study evaluated responses in the leaf anatomy of Alternaria solani infected (IN) and non-infected (NIN) tomato (Solanum lycopersicum) to moringa leaf extract (MLE) application; the responses were then correlated with fruit yield. MLE concentrations of 0.5, 0.75 and 1.5 kg L−1 (w/v) were prepared. Controls were distilled water (negative) and 50 mg L−1 benzylanimopurine cytokinin (positive). Significant interactions were observed for stomatal density (p < 0.001). MLE increased lamina thickness, stomatal density, stomatal size and yield. There was a strong positive correlation between yield, stomatal density, stomatal size and lamina thickness. Stomatal density showed the strongest correlation (r = 0.7979) with fruit yield.

Moringa (Moringa oleifera) leaf extracts inhibit spore germination of Alternaria solani, causal agent of early blight disease of tomato (Solanum lycopersicum)

Alternaria solani is highly infective and can sporulate on tomato at 13.2 × 106 spores mL−1. The fungicidal effect of Moringa oleifera leaf chloroform and aqueous extracts (MLCE and MLAE, respectively) was investigated in vitro to determine the inhibitory effect on germination of spores (conidia) of A. solani. Mixtures of spore suspension and MLCE, as well as MLAE (1:1), were prepared and dropped on slides by micropipette with 20 µL spore suspension of A. solani and 20 µL of MLCE and MLAE. The two treatments, MLCE and MLAE, were applied at four concentrations (62.5, 125, 250 and 500 mg mL−1) and compared with negative (distilled water; no extracts) and positive (diflucan, a commercial fungicide) controls with five replicates. The two extracts showed relatively high inhibitory effects on the germination of conidia from the lowest to the highest concentration. Germination of conidia decreased with increase in the concentrations of the extracts. The study showed that 250 mg mL−1 is the optimum concentration for both MLCE and MLAE. The highest concentration inhibited germination (0.0%) in both extracts. Based on the results from the present study, MLCE and MLAE are both effective in inhibiting germination of A. solani conidia.