Department of Agronomy

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Browsing Department of Agronomy by browse.metadata.advisor "Combrinck, Nicolaas"

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    Effect of magnesium and boron on potato tuber quality
    (Stellenbosch : Stellenbosch University, 2022-04) Hindley, Renoir; Le Roux, Marcellous; Combrinck, Nicolaas; Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy.
    ENGLISH ABSTRACT: Magnesium (Mg) is an important macronutrient with the main function of facilitating various biochemical reactions and physiological responses throughout the development of plants. Magnesium serves as the central atom of chlorophyll molecules in green tissues, contributing extensively to plant assimilation. However, Mg-related studies in potato nutrition, particularly in terms of keeping quality, are poorly documented. Boron (B) is another nutrient that is often overlooked. This nutrient acts as a stabilizer of the cell wall pectin network and as a result enhances cell wall structure. Boron also facilitates the movement of sugar in the plant by forming sugar borate complexes or by linking with the cell membrane in order to enhance sugar permeability. The conversion of starch-to-sugar in tubers is known to affect the nutritional value of potatoes. In this study, greenhouse experiments were conducted to evaluate the influence of different levels of Mg and B against various parameters of potato tuber quality. Magnesium was shown to have a positive response on tuber weight and a shortage of it was detrimental to the storability of tubers. The most significant finding for B was its moderate improvement of starch content in tubers. In the first experiment, two cultivars were evaluated. Tuber number for each treatment combination was determined on day of harvesting. Tuber weight and specific gravity (SG) were performed using a weighing scale and the water displacement method, respectively. The harvests were stored in a dark room, at room temperature, for a six-week period in order to monitor the rate of weight loss. This was obtained by routinely weighing tubers on days 0, 7, 14, 21, 28, and 42 after harvesting. Thereafter, tubers were sent for starch determination that was done by means of the AMG / α-amylase / HK method. In the second experiment, the study to determine the effect of Mg and B in tuber quality was extended. In addition to number, weight, storage losses, and starch content, tubers were divided into weight classes of 50-100 g and 100-150 g, in order to analyse elemental distribution and periderm thickness, respectively. The distribution of elements was accomplished using a Scanning Electron Microscope (SEM). Potato samples that were used for the analysis of periderm thickness, was done by the help of MicroCT scans. The visualization of these samples was performed in Volume Graphics VGStudioMax 3.1. Taking into account the work of Rian Gericke (2018) in predicting the keeping quality of potato by way of tuber characteristics, where Mg correlated negatively with weight loss, the hypothesis in this study that Mg content would have a positive effect on the storage quality of tubers was true. Boron was shown to moderately improve starch content. The distribution analysis showing that Mg tended to locate near the stem-end, at a decreasing gradient towards the bud-end of tubers, was consistent with several previous studies. Unfortunately, the low levels of B were not detected in any of the samples by this method. In comparison to foliar applications, the supply of Mg through the soil was shown to have a more significant influence on periderm thickness, whereas the effect of B was unclear.