Influence of growth regulators on yield, bioactive compounds and postharvest quality of hydroponically grown yellow sweet peppers (Capsicum annum L.)
Mbandlwa, Noxolo Perl
Mbandlwa, Noxolo Perl
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Abstract
Sweet pepper (Capsicum annuum L.) is widely cultivated around the globe for their colour, flavour and nutritional value. Yellow sweet peppers are exceptionally high in carotenoid and ascorbic acid content. However, reduction in yields at harvest and losses during postharvest storage are experienced due to poor agronomic practices and harvesting methods. The NAA treatment significantly improved the quantity of extra-large (XL) fruits; Kelpak® and GA3 treatment significantly improved the quantity of medium (M) fruits and the number of extra-small (XS) was significantly influenced by GA3 as well as 4-CPA+GA3 treatments. The average mass of medium (M) fruits was significantly increased by Kelpak® and GA3 treatments, whereas the 4-CPA+NAA treatment negatively influenced the mass of M sweet pepper fruits. Total fruit yield (marketable & unmarketable) was not significantly influenced by the PGR and biostimulant treatments. Biomass of pepper plants was significantly influenced by PGR and biostimulant treatments, with GA3 treatments having obtained the highest fresh and dry mass. Kelpak® and NAA+Kelpak® treatments were significantly higher in ascorbic acid concentration at 0 Days. At 7, 14 and 21 Days during postharvest storage (at 7.5 ⁰C & 90% RH), the same treatments had significantly higher ascorbic acid content when compared to other treatments. Kelpak® treatment had the highest concentration of total phenols, followed by combined application of NAA+Kelpak®. The total phenol content increased with increasing storage life. Kelpak® treated fruits had healthier looking fruits, with reduced disease incidence at 21 days. The phenolic content and lower antioxidant activity in control treatment fruits were observed from the disease occurrence and severity. The highest antioxidant activity was obtained with NAA treatment followed by Kelpak®. Kelpak® negatively influenced the concentration of carotenoids. However, the highest concentration of carotenoids was detected in NAA+Kelpak®. NAA+Kelpak® had significantly (p < 0.05) higher concentrations of TSS in comparison to all other treatments. NAA+Kelpak® treatment had the highest fruit weight loss whilst Kelpak® treatment had the lowest fruit weight loss during postharvest storage. NAA and Kelpak® sole treatments had the lowest weight loss and moderate fruit firmness when compared to other treatments. Up to day 7, the Kelpak® spayed fruits showed lower carotenoid and higher h ° value indicating the skin colour more towards the greenish yellow. NAA+Kelpak® sprayed fruit showed lower carotenoids and lower h ° value relating to the yellow skin colour on day 7. This study illustrated the influence of PGR and biostimulant treatments on the improvement of plant growth and development and their impact to shelf life and fruit quality of yellow sweet peppers.
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Submitted in partial fulfilment of the requirements for the degree Magister Technologiae Agriculture in the Department of Crop Sciences, Faculty of Science at the Tshwane University of Technology
Date
2018-03
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Tshwane University of Technology
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Keywords
Capsicum annuum L, Stomatal conductance, Fruit yield, Phytochemical content, PGRs