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University of Pretoria (2017)

Evaluation of morpho-agronomic and nutrient variability in germplasm collection of Corchorus spp. in South Africa

Dube, Sweetbird Phindile

Titre : Evaluation of morpho-agronomic and nutrient variability in germplasm collection of Corchorus spp. in South Africa

Auteur : Dube, Sweetbird Phindile

Université de soutenance : University of Pretoria

Grade : Master of Science MSc (Agric) Agronomy 2017

Résumé
South Africa is known as food secure at a national level producing enough food coupled with the ability to import food if necessary to meet food and nutritional requirements of its population. However, the same cannot be said at a household level. Several rural households are still suffering from hunger, malnutrition, and poverty. One of the ways in which rural households can alleviate food insecurity and malnutrition is to increase the consumption of neglected indigenous vegetables such as Corchorus species. Corchorus has been reported to be rich in nutrients such as beta-carotene, Fe, Zn, Ca, Mg and could play an important role by providing relish with considerable amounts of nutrients to poor households. Its use as a food crop needs to be promoted and for this to be achieved there is a need to understand genetic background and generate knowledge for cultivation through plant breeding and precision agronomic studies. This study was therefore, undertaken to assess the genetic diversity and identify potential parents for future use in a Corchorus breeding program in the country. Eleven Corchorus accessions were sourced from Agricultural Research Council (ARC) and World Vegetable Centre (WVC) Taiwan, were evaluated in a field for morpho-agronomic and nutritional traits using a randomised complete block design with three replications across two cropping seasons in 2015/2016 and 2016/2017. The evaluated Corchorus accessions showed significant (P < 0.05) differences among them in both morphological and nutritional traits evaluated. Qualitative morphological characters were highly diversified in leaf colour, leaf shape, stem colour, pod and seed colour based on Shannon Weaver diversity index analysis. The multivariate analysis was used to determine the patterns of diversity among accessions. Morpho-agronomic traits for the first two principal components (PCs) accounted for 78.46% of the total variance and identified days to 50% flowering, plant height, canopy width, leaf length-leaf width ratio, leaf length, number of branches, stem diameter, pod diameter, number of pods, and number of seeds per pod as the most contributors to variation in the germplasm. Whereas for the nutritional traits the first two principal components accounted for 70.93% of the total variance with K, Ca, Mg, P, Fe, Mn, B, and Cu contributing most to variability. High level of variability was observed from the principal component biplot and cluster analysis among accessions. The ARC and WVC accessions were clustered into two different groups based on morphological traits. Genetic parameters were estimated for morphological quantitative and nutritional traits and showed considerable amount of genetic variability. High genotypic coefficient of variation (GCV), broad sense heritability (H2), and genetic advance (GA) were computed for plant height (59.2%, 89.2%, and 115.1), number of leaves per plant (39.7%, 74.7%, and 70.6), pod length (49.0%, 97.0% and 99.4), number of pods (144.4%, 80.1%, and 266.3), number of seeds per pod (54.1%, 88.4%, and 104.9), calcium (22.3%, 82.1%, and 41.6), magnesium (34.4%, 89.3%, and 66.9), and phosphorus (25.8%, 75.8% and 41.3), respectively, which permits effective selection. This study revealed sufficient genetic variability both for qualitative and quantitative morphological and nutritional characters among the Corchorus accessions, which could be exploited for the improvement in the Corchorus breeding programme in South Africa.

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