Thesis (M.Sc. (Horticulture)) -- University of Limpopo, 2022 / The South African Avocado Industry has recently announced plans to expand
exports into new markets, such as the United States (US). As a requirement for
these markets, fruit of high quality must be stored at ultra-low temperature to mitigate
phytosanitary risks. However, ‘Hass’ avocado fruit are susceptible to chilling injury
when stored at temperatures below 3°C. Moreover, CI development resulted in
uneven ripening and disease infestation due to damaged cell membranes.
Therefore, the objective of this study was to evaluate the potential of methyl
jasmonate (MeJA) and salicylic acid (SA) on quality maintenance of 'Hass' avocado
fruit during ultra-low cold storage. Matured ‘Hass’ avocado fruit were harvested at
commercial dry matter (22%). The experiment was conducted using a completely
randomized design (CRD) with eight replications per treatment. Treatment
concentrations for methyl jasmonate (MeJA) were 0 (control), 10 and 100 μmol•L−1
,
while those for salicylic acid (SA) were 0 (control), 1.0, 2.0 and 3.0 mM. After
treatments, fruit were stored at 2°C for 31 days and thereafter, ripened at ambient
temperature (±25°C) until fully ripe. During ripening, fruit were evaluated for weight
loss, exocarp colour, firmness, chilling injury, as well as physiological (vascular
browning) and pathological disorders (fruit rot). In this study, dipping fruit in MeJA
solution significantly (P < 0.05) reduced ‘Hass’ avocado fruit firmness loss.
Moreover, MeJA showed a significant effect (P < 0.05) on hue angle (h°) but did not
significantly affect (P > 0.05) visual colour rating, chroma (C*), lightness (L*) and
weight loss. The results showed that ‘Hass’ avocado fruit treated with 10 μmol•L−1
MeJA reduced weight loss when compared with 100 μmol•L−1 MeJA from day 2 to
day 8 of ripening. Overall results showed a visual change in ‘Hass’ avocado fruit
exocarp colour, with eye colour changing from rating 1 (emerald-green) to 3 (olive-
green) for control and fruit treated with MeJA throughout the ripening days.
Furthermore, MeJA reduced ‘Hass’ avocado fruit external chilling injury,
physiological and pathological disorders. With respect to SA treatments, the result
showed that dipping fruit at 1.0 and 2.0 mM SA had a significant effect (P < 0.05) on
reducing firmness loss during ripening. Salicylic acid (1.0 mM) reduced and
alleviated ‘Hass’ avocado fruit external chilling injury during ultra-low cold storage.
Furthermore, result showed that 1.0 and 2.0 mM SA treatments had significant affect
(P < 0.05) on firmness loss. Moreover, a significant effect was observed on visual
colour and C* but did not affect (P > 0.05) L* and h°. Fruit treated with SA showed
poor exocarp colour development with extended exposure to ultra-low cold storage,
as a result, developed chilling symptoms. The treatment of ‘Hass’ avocado fruit with
1.0 mM SA inhibited the incidence of fruit rot and vascular browning when compared
with control and fruit treated with 2.0 and 3.0 mM SA. In conclusion, 10 and 100
μmol•L−1 MeJA and 1.0, 2.0 and 3.0 mM SA effectively preserved ‘Hass’ avocado
fruit quality during storage at ultra-low temperature. / Agricultural Sector Education Training Authority (AgriSeta) and
National Research Foundation (NRF)
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ul/oai:ulspace.ul.ac.za:10386/3978 |
| Date | January 2022 |
| Creators | Monyela, Ngoako Frans. |
| Contributors | Mathaba, N., Mafeo, T. P. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | xi, 75 leaves |
| Relation |
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