Variability and heritability of nutritional composition among L. siceraria landraces from Northern KwaZulu-Natal, South Africa | IJAAR 2020
Lagenaria siceraria (Molina) Standley of the Cucurbitaceae family has nutritious tender shoots, fruits, and seeds that are of culinary use in rural communities as vegetables. However, no studies on variation, correlation, heritability, and genetic advance of its nutritional traits were conducted in northern KwaZulu-Natal, South Africa. This study aimed to characterize nutritional variability and heritability among L. siceraria genotypes from different origins. Nutritional traits were compared among different landraces using ANOVA, correlation, principal component analysis, cluster analysis, and heritability estimates. Landraces varied significantly in their nutritional traits. Significant positive correlations were recorded among nutritional traits. The first three informative principal components had a total variability of 80.270%. Landraces in a biplot and dendrogram clustered closely to the nutritional components they strongly relate with, either positively or negatively. In five distinct clusters, landraces NRC, KSP, and NRB were singletons in Clusters I, II, and V, respectively. Cluster (III) consisted of NqSC, KSC, KRI, NSRC, and DSI; whereas Cluster IV grouped landraces NSRC, RRP, MSC, NSRP, NqRC, and RSP. High heritability estimates and genetic advances were recorded among nutritional traits. Therefore, this study serves as a reference for potential L. siceraria germplasm with ideal nutritional composition for future breeding programs.
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Materials and methods Collection and study area Germplasm for the study represented of 14 L. siceraria landraces that were collected from Dundee (28.1650° S, 30.2343° E), Khangelani (29.0106° S, 31.2211° E), Mbazwana (27.4937° S, 32.5882° E), Ndumo (26.9342° S, 32.2824° E), Nquthu (28.2195° S, 30.6746° E) and Rorke’s Drift (28.3492° S, 30.5351° E) in northern KZN. Landrace names were coined according to their origin as well as fruit and seed morphology (Table 1). The field experiment was conducted at the University of Zululand, KwaDlangezwa Campus (28.8530° S, 31.8500° E), which has a sub–tropical climate (Ntuli and Zobolo 2008). The KwaDlangezwa area has a daily mean temperature of 28.4°C in summer and 14.5°C in winter (Nelson et al., 2014). This study was conducted over two summer seasons (September 2016–February 2017) and (September 2017–February 2018), in a complete randomized block design. Design and sampling procedures Eighty (80) seeds from each of the 14 landraces were sown onto the plug trays and irrigated to plug tray capacity two to three times per week. At 31 days after sowing (31 DAS) all 14 landraces were at first to second true leaf stage and were transplanted onto a 1050m2 plot of land with three replicate plots randomly assayed for each of the 14 landraces, corresponding to 42 plots within the 1050 m2 in total. Each plot was 9m2 in area with 2m inter-plot spacing and 1m intra-row spacing, housing 16 plants per plot and 672 plants in total. At transplanting, fertilizer NPK 2:3:4 (30) at a rate of 40g/m2 was applied below the seedlings in 10–15-cm-deep pits and the field was irrigated to capacity. At 31 days after transplant (DAT), nitrogen fertilizer (limestone ammonium nitrate (LAN 28)) at the same rate was band placed around each plant. Plants were irrigated adequately depending on the amount of rainfall and temperature. Weeding and insecticides applications were performed when necessary.