Browsing by Author "Ntuli, Nontuthuko Rosemary"

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    Genetic improvement of selected indigenous Cucurbitaceae species important for food and medicinal purposes in KwaZulu-Natal, South Africa
    (2007) Ntuli, Nontuthuko Rosemary; Ferreira, D.P.; Hannweg, K.; Zobolo, A.M.
    Coccinia palmata (Cogn.) and Lagenaha sphaerica (Sond.) Naud. are indigenous Cucurbitaceae species widely distributed in pantropical to tropical regions of Southern Africa. They are widely used for food and medicinal purposes, in nature these species exist as diploids, with their basic haploid (n) chromosome numbers being 12 and 11 for C. palmata and L sphaerica respectively. However, in higher plants nuclear DNA endoreduplication often occurs during their growth and differentiation which causes polysomaty in their tissues. For both C. palmata and L sphaerica, the optimum germination conditions were 25°C under light. Growth was either in the nursery (in pots/bags) or in the field (with and without bags). Colchicine treatment of seeds before and after incubation for germination was used to induce polyploidy in both of these Cucurbitaceae species. The effectiveness of colchicine in inducing polyploidy (genetic improvement) in the roots and shoots of both species was established. In both species treated roots had higher tetraploid and octoploid ratios than leaves. Colchicine treatment lowered the germinability (germination percentage), induced dwarfism, enhanced stem branching, reduced leaf area and number of stomata, and increased guard cell length and leaf chlorophyll content in both species. In C. palmata, colchicine treatment increased root fresh and dry weight but reduced shoot fresh and dry weight. However, colchicine treatment inhibited female plants' flowering and therefore fruiting in both species.
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    A survey of traditional leafy vegetables and studies of genetic diversity of Cucurbita landraces in northern KwaZulu-Natal, South Africa
    (University of Zululand, 2013) Ntuli, Nontuthuko Rosemary; Zobolo, A.M.; Madakadze, R.M.; Tongoona, P.B.
    Traditional leafy vegetables (TLVs) are commonly herbaceous plants with relatively high nutrition and health significance. They have formed part of food security in rural-based communities for generations. The utilization of TLVs; the diversity in morphology, yield and genetics of highly preferred vegetable species was investigated. The objectives were to identify the known and preferred TLVs, and determine morphology, yield and genetic diversity of most preferred Cucurbita landraces in northern KwaZulu-Natal. In a total of 72 recorded species, the following were recorded for the first time as TLVs: Commelina erecta, Deinbollia oblongifolia, Erythroxylum delagoense, Galinsoga ciliata, Ipomoea wightii, Limeum sulcatum, Priva meyeri var. meyeri, Trachyandra asperata var. asperata and Trachyandra cf. saltii var. saltii. High species diversity was recorded at Umkhanyakude district when compared with others. Most vegetables were collected from the wild, during rainy seasons, and were consumed daily to every two days. Cucurbita species were predominantly grown in spring and summer, from the seeds that were saved from the previous harvest. Leafy shoots were harvested in less than two months from seeding. Diversity in morphology and yield was evident in landraces within the same and among different Cucurbita species. Cucurbita pepo landraces had the highest shoot, fruit and seed yields. In all Cucurbita landraces, harvest-pruning initiated at six weeks from planting resulted in longer vines and higher numbers of: lateral branches; leaves; pistillate and staminate flowers. Dendrogram from molecular analysis using random amplified polymorphic DNA (RAPD) markers primarily grouped C. pepo landraces according to the fruit colour change at maturity, while both RAPD and simple sequence repeat (SSR) markers also grouped them according to their agro-ecological origin. Some unique RAPD and SSR bands discriminated the self-pollinated C. pepo landraces from the unselfed ones. The newly documented TLVs have formed the basis for future research of their growth, yield as well as improved palatability. Also the results of diversity in morphology and genetics of Cucurbita landraces can be used to improve these vegetable species.