Browsing by Author "Jordaan, Stephen Christiaan"

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    The impact of protective netting on reproductive bud development, flowering, fruit set and fruit quality in apple trees
    (Stellenbosch : Stellenbosch University, 2023-03) Jordaan, Stephen Christiaan; Midgley, S. J. E.; Lotze, Elmi; Stellenbosch University. Faculty of Agrisciences. Dept. of Horticulture.
    ENGLISH ABSTRACT: The overall objective of this study was to determine how yield, fruit quality and maturity, reproductive bud development, flowering, fruit set and early fruit growth of apple orchards are impacted by two types of protective netting compared to open orchards, in the Western Cape Province of South Africa. The study also aimed to investigate the interactive effects between black draped netting and various levels of crop load on reproductive processes of ‘Golden Delicious’ trees. To achieve these aims, three trials were conducted over two seasons. In the first trial, fixed white (20%) netting over ‘Rosy Glow’ resulted in improved fruit growth rate, increased fruit diameter and mass, lighter green ground colour, less peel red colour, lower viable seed count, and less sunburn and hail damage in two consecutive seasons. The netting did not induce any significant effect on percentage reproductive buds (R-buds), R-bud progression for different shoot types, flower progression, flower quality, and early fruit growth. A small but significant reduction in fruit set percentage under netting was, however, found. In the second trial, black draped netting (end-November to end-February) over ‘Golden Delicious Reinders’ resulted in greener fruit, less sunburn and hail damage, reduced firmness, and reduced ratio of total soluble solids (TSS) to titratable acidity (TA). R-bud percentage was promoted under the netting; however, R-bud progression was delayed after net removal. The latter effect may have culminated in delayed flowering, lowered fruit set (farm data) and reduced early fruit growth. In the third trial, black draped netting (mid-December to early March) over ‘Golden Delicious’ resulted in more stem-end russet, greener ground colour, lower firmness and advanced starch breakdown, fewer viable seed, less sunburn, and lower TSS and TA. Significant interactions between net/control and crop load treatments were found for ground colour, TA and TSS:TA. R-bud percentage was higher and more uniform across all crop loads and shoot types under the netting, while the control treatment displayed an increasing R-bud percentage for decreasing crop load level across most shoot types. After the harvest and net removal, R-bud progression was slightly but significantly delayed. Flower progression was unaffected by the netting. For flower quality, significant interaction between flower type and netting was found for pedicel length, receptacle length and number of locules. In addition, significant interaction between net/control and crop load treatments was found for ovule length. Fruit set percentage improved under netting. The different crop load levels did not have a significant impact on flower progression, flower quality and fruit set. The use of both fixed and draped netting in apple orchards has the potential to improve apple fruit quality. However, caution is required based on the impact of draped netting on flowering and reproductive growth during the following season in ‘Golden Delicious’ and its strains. Crop load adjustments are recommended in ‘Golden Delicious’ and its strains to minimise the impact of netting on reproductive growth during the current and following season.