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Effect of Environmental Conditions at
Harvest on the Incidence of Lenticel
Damage in MalJgo
S.A. Oosthuyse
HortResearch SA, P.O. Box 3849, Tzaneen 0850
ABSTRACT
Lenticel damage is a common problem whose incidence is thought to be affected by many of the conditions to which
mango fruits are exposed prior to, during and after harvest. The effects on the postharvest incidence of lenticel
damage of air temperature, relative humidity, hours of direct solar radiation, amount of wind, and amount of rain
on the day of harvest were assessed in the present study.
Fruits of the cultivars Heidi, Sensation, Kent, Keitt, Tommy Atkins and Zill were harvested weekly from the same
trees over a period of 4 or 5 weeks. Conditions on the day of harvest were obtained from a weather station situated
in the vicinity of the trees used. Lenticel damage incidence was estimated on fruit ripening following commercial
packline treatment, cool-storage at 9.5C for four weeks, and post-storage ripening at 20C.
Strong negative correlations were generally found with maximum temperature, minimum temperature, and Class
A Pan evaporation. Strong positive correlations were generally found with maximum humidity. Rain at harvest only
occurred in Tommy Atkins. A correlation coefficient of almost 1 was found with amount of rain. The results dearly
indicate that cool, humid or wet conditions on the date of harvest strongly favour the postharvest occurrence of
lenticel damage. Conversely, dry, hot conditions were indicated to disfavour the postharvest occurrence of lenticel
damage.
UITTREKSEL
Lentiselskade is 'n algemene probleem, en die voorkoms daarvan word vermoedelik beinvloed deur toestande
waaraan mangoes blootgestel word voor, gedurende en na pluktyd. Die effek op die voorkoms van lentiselskade deur
temperatuur,
relatiewe humiditeit, ure van direkte sonbestraling, Class A Pan verdamping, hoeveelheid wind, en
reen gedurende die dag van pluk, is in die studie vasgestel.
Vrugte van Heidi, Sensation, Kent, Keitt, Tommy Atkins en Zill is weekliks oor 'n tydperk van 4 of 5 weke van
dieselfde borne gepluk. Weerstoestande
op die plukdag is verkry van 'n weerstasie wat in die omgewing van die
bepaalde borne opgerig is. Die voorkoms van lentiselskade is geskat op vrugte wat pakhuisbehandeling
ondergaan
het, vir 4 weke teen 9.5C in 'n koelkamer geberg is, en na-berging rypmaking teen 20C ondergaan het.
Daar is sterk negatiewe ooreenkomste gevind in maksimum temperature, minimum temperature en Class A Pan
verdamping. Sterk positiewe ooreenkomste het met maksimum humiditeit voorgekom. Toe Tommy Atkins-vrugte
gepluk is, het reen voorgekom. 'n Korrelasie-koofisient
in van amper 1 is met die hoeveelheid reen gevind. Die
resultate het duidelik aangedui dat koel, klam of nat toestande op die plukdag, die voorkoms van lentiselskade
begunstig. Daarenteen is droe, warm toes tan de ongunstig vir die na-oes ontwikkeling van lentiselskade.
Lenticel damage is evidenced by the darkening oftissue
immediately surrounding lenticels on the skin of mango
fruits (Fig. I). Although internal quality is not affected, a
detraction in appearance results. Damaged lenticels on fruits
generally become apparent shortly after the initiation of
cool-storage (pers. obs.). Lenticel damage may also be
noticed prior to the commencement of cool-storage (pers.
obs.). Often it is most conspicuous on skin regions having
been exposed to sap flow (pers. obs.). Lenticels having
become exposed to sap may become sunken, this occurrence
giving rise to the disorder referred to as pitted spot (Oosthuyse, 1993). Varieties apparently differ in their susceptibility (Donkin and Oosthuyse, 1996). The lenticels on
Tommy Atkins and Keitt fruits appear to particularly be
prone to damage (pers. obs.).
The incidence of lenticel damage has been found to be
reduced by hydro-heating at 50C for 5 or 7 minutes (Oosthuyse, 1996). Enhanced damage has been associated with
Fig. 1 Lenticel damage is evidenced by the darkening of
tissue immediately surrounding lenticels on the skin of
mango fruits.
postharvest hydro-heating treatments (Jacobi et al. 1996a,
1996b). A reduction was found when fruits were pre-conditioned by hydro-heating at a reduced temperature (Jacobi et
al., 1996a). Pre-storage of Zill fruits at 20C for 72 hours
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n"lin T
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Fig. 2 Plot of correlation coefficients for the correlations between maximum temperature (max T), minimum temperature
(min T), amount of rain (rain), Class A Pan evaporation (evap), number of sunshine hours (suns), total wind (tot wind),
maximum humidity (max H) or minimum humidity (min H) andfruit lenticel damage incidence.
prior to cool-storage was found to reduce the sensitivity of
lenticels to damage (Oosthuyse, 1994).
Postharvest calcium infiltration of mango fruit under
low pressure has resulted in lenticel damage (Joyce and
Shorter, 1996). Gamma-irradiation exposure of harvested
fruits has been found to induce lenticel damage (McLauchlan et ai., 1990; Johnson et ai., 1990; Lonsdale et ai., 1990;
Lonsdale, 1992).
Research findings concerning the effect of pre-harvest
and harvest environmental conditions on the postharvest
incidence of lenticel damage are lacking.
In the present study, the effect of environmental conditions on the day of harvest on the fruit incidence of lenticel
damage after extended cool-storage was assessed in a
number of mango cultivars.
Fruits of the cultivars Heidi, Sensation, Kent, Keitt,
Tommy Atkins and Zill were harvested weekly over a
period of four or five weeks. In each cultivar, fruits were
harvested on each date from the same trees. The trees were
adjacent to one another in an orchard row. The fruits were
harvested whilst walking around each of the trees used. The
number of trees in each instance varied from 4 to 8.
The trees were on a commercial farm in the Hoedspruit
region, and were situated within 15 km of the weather
station used. On each harvest date, maximum temperature,
minimum temperature, Class- A Pan evaporation, number of
sunshine hours, total wind, maximum humidity, minimum
humidity and total rainfall were obtained.
Eighty to 100 fruits of each cultivar were harvested from
the time harvest maturation was attained. They were subjected to the commercial packline treatment [I % BiProx
soap wash, clear water rinse, hydro-heating at 50C for 5
minutes, 20 second dip in Omega solution (180 ml per 100
I water), waxing with TAG]. Immediately after this treatment, the fruits were placed in cool-storage at 9.5C for 28
days. Packline treatment and placement in cool-storage
were accomplished within 24 hours of harvest. After coolstorage, the fruits were allowed to ripen further at 20C.
When the firm-ripe stage was generally attained, lenticel
damage was assessed.
Lenticel damage incidence was estimated by approximating the percentage of the skin covered by damaged
lenticels. Estimates given were either 0,15,50,75 or 100%.
The estimates were subjected to correlation analysis, stipulating each of the environmental parameters obtained as the
independent variate.
Correlations between harvest date and lenticel damage
incidence were attitionally determined to test the assumption of harvest date not influencing susceptibility to lenticel
damage.
There was no clear indication ofthe incidence oflenticel
damage after harvest being positively or negatively correlated with harvest date in any of the cultivars used (data not
shown).
Fig. 2 shows the correlation coefficients found for the
relationships between the incidence of lenticel damage and
maximum day temperature, minimum day temperature,
amount of rain, Class A Pan evaporation, number of sunshine hours, total wind, maximum humidity or minimum
humidity.
Strong negative correlations were generally found with
maximum temperature, minimum temperature (the higher
minima were associated with less damage), or Class A Pan
evaporation. Strong positive correlations were generally
found with maximum humidity. Rain at harvest only occurred in Tommy Atkins. Here, a correlation coefficient of
almost 1 was found.
The results clearly indicate that cool, humid or wet
conditions on the date of harvest strongly favour the postharvest occurrence of lenticel damage. Conversely, dry, hot
conditions were indicated to disfavour the postharvest occurrence of lenticel damage. The associations found with
maximum temperature, minimum temperature. maximum
humidity and evaporative demand strongly support these
conclusions.
In view of the results, it might be advised that mango
growers refrain from harvesting their fruits on days which
are overcast or wet, or on days when the relative humidity
is high as a result of recent rain.
DONKIN. D.J. AND OOSTHUYSE, SA 1996. Quality
evaluations of sea-exported South African mangoes in
Europe during the 1995/96 season. S.A. Mango Growers'
Assoc. Yearbook 16:1-5.
JACOBI, K.K., WONG, L.S., AND GILES, J.E. 1996a.
Effect of hot air disinfestation treatment in combination
with simulated air freight conditions on quality of
'Kensington' mango (Mangifera indica Linn.). Aust. 1.
Kept. Agric. 36:739-745.
JACOBI, K.K., WONG, L.S., AND GILES, J.E. 1996b.
Conditioning with hot air reduces heat damage caused to
'Kensington' mango (Mangifera indica Linn.) by hot water
disinfestation treatment. Aust. 1. Expt. Agric. 36:507-512.
JOHNSON, G.!., BOAG, T.S., COOKE, A.W .. IZARD,
M., PANITZ, M., AND SANGCHOTE, S. 1990. Interaction of post harvest disease control treatments and gamma
irradiation on mangoes. Ann. Appl. BioI. 116:245-257.
JOYCE, D.C. AND SHORTER, A.J. 1996. Partial pressure
calcium infiltration of mangoes did not delay softening.
Proc. Australasian Postharvest Horticulture Conference,
Melbourne, Australia (1995).
LONSDALE, J.H. 1992. In search of an effective postharvest treatment for the control of postharvest diseases of
mangoes. SA Mango Growers' Assoc. Yearbook 12:32-36.
LONSDALE. J.H., LONSDALE. J.M., GOUGH, T .. AND
LUNT, R.E. 1991. Control of postharvest decay of mangoes
using hot water in combination with radurisation or modified atmosphere packaging. S.A. Mango Growers' Assoc.
Yearbook 11:42-44.
MCLAUCHLAN, R.L., MITCHELL, G.E., JOHNSON,
G.!., AND WILLS, P.A. 1990. Irradiation of Kensington
Pride mangoes. Acta Hort. 269:469-476.
OOSTHUYSE. S.A. 1993. Disorders of fibreless mangoes
grown in South Africa for export. SA. Mango Growers'
Assoc. Yearbook 13:80-88.
OOSTHUYSE. S.A. 1994. Quality of mature Zill mangoes
after long-term refrigerated storage as determined by prestorage ripeness and cold-storage regime. S.A. Mango
Growers' Assoc. Yearbook 14: 37-42.
OOSTHUYSE, SA 1996. Effect of packline hydro-heating
treatments on Heidi fruit quality after four weeks of coldstorage. S.A. Mango Growers' Assoc. Yearbook 16:6-11.
Ilf)(JI~IIS
ONS VERV AARDIG 'N WYE REEKS KARTONNE VIR DIE
LANDBOUBEDRYF
* Sitrus * Piesangs * Tamaties *
Mango's
* Avokado's * Litchi's *
Spanspek
* Ander groente- en vrugtekartonne
*
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