Mardé Booyse

Physico-chemical, microbiological, textural and sensory attributes of matured game salami produced from springbok (Antidorcas marsupialis), gemsbok (Oryx gazella), kudu (Tragelaphus strepsiceros) and zebra (Equus burchelli) harvested in Namibia

Differences and consumer acceptability of matured salami produced from game species were evaluated. The pH of the salami differed (p < 0.05) with springbok salami having the highest mean pH value. No differences (p > 0.05) were observed among the species for a(w), shear force, gumminess or cohesiveness. Microbiological counts of the game salami differed for coliform (p < 0.05) but not for E. coli (p > 0.05) counts. The most distinctive characteristics observed by the quantitative descriptive analyses were smoky, salty, pepper and salami flavour, combined with a smoky, salami aroma. Game flavour was not perceived as a strong attribute during the sensory analyses. Gemsbok salami was strongly associated with the attribute colour as described by the male and female consumer panels. The springbok salami scored the lowest for both colour and taste. Salami produced from gemsbok, kudu and zebra were superior to springbok salami.

Inheritance of flavour in six tomato (Lycopersicon esculentum) varieties

Flavour component differences between six tomato varieties and their F1, progenies were investigated. A diallel crossing system, excluding the reciprocal crosses was used. The F-1 and parent varieties were compared by carrying out a sensory evaluation and a chemical component analysis. Statistical analysis of these two data sets revealed significant differences among the F1 and parents for the chemical analysis variables, whereas the sensory variables showed considerably fewer significant differences. The number of correlations found between the chemical analysis and the sensory evaluation were relatively few. In the combining ability analysis, all the chemical analysis variables showed significant differences for general combining ability and specific combining ability. None of the sensory variables showed significant differences for specific combining ability and only one sensory variable, juiciness, showed highly significant differences for general combining ability. Both types of analyses, chemical an...

Valuable Russian wheat aphid-resistant bread wheat accessions identified using four South African Diuraphis noxia biotypes

Resistance-breaking biotypes of Diuraphis noxia have been reported in both the USA and South Africa where commercial cultivars with genetic resistance to this pest have been deployed. The need to identify novel Russian wheat aphid (RWA) resistance for deployment against new biotypes of RWA has driven the recent re-evaluation and characterisation of resistance in landraces of bread wheat from germplasm collections worldwide. Twenty-three genotypes already in use in a South African pre-breeding programme were evaluated with the extended spectrum of South African RWA biotypes, while four genotypes not yet tested with South African RWA were screened with RWASA1, RWASA2, RWASA3 and RWASA4 for the first time. Five accessions, namely PI 94355, PI 243781, PI 361836, PI 626580 and the check CItr 2401, were resistant to all four South African RWA biotypes. The previously unused accessions PI 094355 and PI 243781 will be incorporated into the programme. The sixth accession resistant to RWASA4, namely PI 366518, is susceptible to RWASA2 and RWASA3 and may possibly be unique, meriting emphasis in pre-breeding activities. The use of multiple, distinct resistance genes, including those with a moderate resistance reaction, is seen as the most responsible strategy for the stewardship of genetic resistance to RWA in bread wheat.

Employing the GGE SREG model plus Elston index values for multiple trait selection in sweetpotato

Sweetpotato is a good source of energy, easy-to-grow and hardy and thus useful in contributing to food security. The current study aimed at identification of the best sweetpotato varieties for multiple desirable traits such as good yield, adaptability (including vine vigor) and tastiness (high dry mass content; taste). Ten South African sweetpotato varieties were evaluated during the period 2002/3–2007/8 at six locations each over two seasons. The sites regression model (SREG) of the genotype plus genotype by environment interaction (GGE) biplot analysis was performed with GenStat to determine stability and adaptability of the varieties. Subsequently, multiple trait selection was performed by using the ranking from Elston index selection. To enable inclusion of varietal stability in multiple trait selection, a stability value was calculated. High yielding varieties included Blesbok, Monate, Ndou and Letlhabula, of which Monate and Letlhabula had stable performance. The advantage, particularly for resource-poor farmers, of a specifically adapted, responsive variety such as Ndou, is the ability to respond to changes in the environment. Based on multiple trait selection varieties Ndou and Monate were recommended for production. The results present an innovative use of Elston index selection, including a stability value, in combination with GGE SREG for recommending varieties with multiple desirable traits. The recommended varieties are of significance for future use to improve food security.

Component dry masses and carbohydrate contents in honeybush I: Cyclopia genistoides

Cyclopia (honeybush), a new and largely unstudied South African horticultural crop, was investigated by carrying out a reconnaissance-level survey of C. genistoides (Cg) populations. Four-year average total dry mass (DM) in plantation-grown Cg cuttings and seedlings, and wild (veld) plants were, respectively, 981, 1 261 and 269 g plant−1. Top growth, thick roots (≥5 mm diameter) and thin roots (<5 mm diameter) constituted 39%, 41% and 20% of total DM in the cuttings, 40%, 43% and 17% in the seedlings, and 51%, 36% and 13% in the wild plants. Total root starch content averaged 13 815 mg (cuttings), 26 771 mg (seedlings) and 5 085 mg (wild plants). Of this starch, 74–80% was located in the thick roots. Thick root:thin root starch content ratios averaged 1.95:1 in the plantations and 3.89:1 in the wild plants, whereas shoot DM:total root DM ratios averaged 0.66:1 in the plantations and 1.03:1 in the wild plants. Starch contents and concentrations were higher between January and March than May to July. To optimise yields and starch contents, Cg should be harvested in autumn rather than summer. Top growth yields per plant in Cg plantations, notably seedlings, exceed those from wild Cg plants.

Efficiency of energy conversion and growth of gamma irradiated embryos and young seedlings of Triticum monococcum L. cultivar Einkorn

Abstract The study was conducted to determine whether the efficiency of energy conversion into growth can be used as an indicator for the determination of the optimal gamma irradiation dosage for mutation breeding. To meet this objective, embryo growth, shoot growth, root growth, mobilization of food reserves, respiration and energy conversion were studied in gamma-irradiated wheat Triticum monococcum L. cultivar Einkorn kernels. Kernels were exposed to 50, 150, 250 and 350 Gy and germinated. Kernels were collected 12 h after onset of imbibition and then every 12 h until 168 h. Irradiated seed demonstrated retardation in all parameters, which increased as the gamma irradiation dosage increased. For the most, dosage and time, as well as dosage by time interaction were highly significant. Root growth appeared to be the most sensitive to gamma irradiation, followed by shoot growth, mobilization of food reserves and efficiency of energy conversion. Full recovery of the efficiency of energy conversion took place at 50 Gy, with an increase in inefficiency with an increase in dosage. The point where full recovery of efficiency of energy conversion into growth gives way to incomplete recovery (100 Gy) is in line with the suggested dosages for practical mutation breeding in Triticum monococcum L. by the FAO/IAEA and is therefore an ideal indicator for predicting the dosage that will be optimal for plant mutation breeding.

Effect of rootstock on ‘Forelle’ pear (Pyrus communis L.) growth and production

European pears (Pyrus communis L.) are predominantly planted either on pear (P. communis) or quince (Cydonia oblonga L.) rootstocks. High-density commercial pear orchards require dwarfing rootstocks and the South African selections BP1 and BP3 were considered too vigorous. The growth and production of the important export cultivar ‘Forelle’ were evaluated on a range of rootstocks at three sites for between seven and nine seasons. In the final season, the trunk cross-sectional area (TCA) of trees on Pyrodwarf (PD), ‘Old Home’ × ‘Farmingdale’ (OHxF) 217, BU2/33, BP3, OHxF40 and BP1 averaged 100.0 cm2, with the smallest trees on Quince C51 (QC51). Trees on PD, OHxF217, BP1 and OHxF40 yielded 30.0 kg tree−1, whereas trees on Quince A (QA) and QC51 yielded <25.0 kg tree−1. Trees with a yield efficiency of 0.29–0.35 kg cm−2 TCA were on OHxF97, PD, QC51, OHxF333 and OHxF217, whereas trees on BP3 had a yield efficiency of 0.21 kg cm−2 TCA. Trees on OHxF217, OHxF40 and BP1 had a cumulative yield of 100.0 kg tree−1, whereas trees on QC51 and QA had a cumulative yield of 60.0 kg tree−1. The best rootstock was OHxF217, followed by OHxF40 and OHxF97. PD and OHxF333 also performed well but were evaluated at one site only.

Component dry masses and carbohydrate contents in honeybush II: Cyclopia subternata

A four-year reconnaissance-level survey was carried out in a honeybush (Cyclopia subternata; Cs) population to obtain information concerning this new South African horticultural crop. Average total dry mass (DM) in Cs cuttings under plantation conditions was 2 481 g plant−1, of which the harvestable top growth (shoots), non-harvestable top growth (stem) and roots constituted 17%, 59% and 24%, respectively. Starch reserves averaged 6 321 mg plant−1, (stem 62%, roots 38%). Corresponding values for Cs seedlings were 3 796 g plant−1 (13%, 62% and 25%) and 10 044 mg plant−1 (69% and 31%). Ratios of shoot DM to non-harvestable DM, and of stem to root starch content were, respectively, 1:4.799 and 1:0.620 in the cuttings, and 1:6.753 and 1:0.447 in the seedlings. Yields of dry shoots averaged 3.6 t ha−1 from the cuttings and 4.2 t ha−1 from the seedlings. Top growth DM and starch reserves were greatest in late summer to autumn. Autumn is therefore the best time to harvest.

Effect of blossom stage of ‘Alpine’ nectarine on efficacy of chemical thinning using Armothin

Fruit thinning of peach and nectarine cultivars is essential to maximize profitability and stabilize production and is routinely done by hand thinning of blossoms and early fruit. Chemical thinning of blossoms may reduce the cost of manual labour, but results are inconsistent and commercialization is lacking. Blossom sensitivity to caustic agents may depend on blossom type and degree of pollination and/or fertilization. Armothin®, a registered blossom thinning agent, was evaluated at 1.5% v/v and 3% v/v applied at 11, 17 and 42% full-bloom, to evaluate the effect of blossom type and the fertilization and/or pollination of blossoms, on thinning of ‘Alpine’ nectarine. The earliest application (11% full-bloom) of 3% v/v Armothin® provided optimum thinning and fruit size. Any blossoms showing pink appear to be removed by Armothin®, while open blossoms are removed irrespective of whether they are fertilised and/or pollinated. The removal of early opening blossoms results in the potential loss in early ripening, higher value fruit especially in an early cultivar. Later maturing blossoms remain to develop into later maturing fruit which tend to be smaller. Thus an early application of 3% Armothin®, when less than 50% blossoms show pink, may provide sufficient blossom thinning to expedite later hand thinning, but does not necessarily remove the need for hand thinning.