The effect of climatic factors at different growth periods on pepino (Solanum muricatum Aiton) fruit quality and yield

Abstract

Pepino, native to South America, is an evergreen, exotic plant species that belongs to the Solanaceae family and has been known and grown for a long time. In the study, the effect of different planting months, April and May in 2004 and 2006, on fruit quality and yield were investigated. Fruit diameter and length, fruit weight, fruit numbers per plant and yield were considered with climatic factors. The experiments were conducted in a split-plot design with three replications, and all data were subjected to statistical evaluation. In 2004 with an April planting time, there were significant differences in fruit diameter, weight, fruit number per plant and yield while fruit length showed numerical difference. With the exception of fruit length, the other parameters did not show statistically significant differences although all data in 2004 were higher than those for 2006 numerically. It could be suggested that in the growing of pepino numerical differences in fruit diameter, fruit weight, fruit number per plant and yield are affected by climatic factors.

Full text

Journal of Food, Agriculture & Environment, Vol.7 (2), April 2009 55 1
The effect of climatic factors at different growth periods on pepino
(Solanum muricatum Aiton) fruit quality and yield
Aysun ÇavuÍo«lu *, Emine s. Erkel and Melekber SülüÍo«lu
Kocaeli University, Arslanbey Agricultural Vocational School, 41285, Kocaeli, Turkey.
*e-mail: cavusoglu@kocaeli.edu.tr, erkel@kocaeli.edu.tr, meleksl@kocaeli.edu.tr
Received 25 January 2009, accepted 11 April 2009.
Abstract
Pepino, native to South America, is an evergreen, exotic plant species that belongs to the Solanaceae family and has been known and grown for a
long time. In the study, the effect of different planting months, April and May in 2004 and 2006, on fruit quality and yield were investigated. Fruit
diameter and length, fruit weight, fruit numbers per plant and yield were considered with climatic factors. The experiments were conducted in a
split-plot design with three replications, and all data were subjected to statistical evaluation. In 2004 with an April planting time, there were
significant differences in fruit diameter, weight, fruit number per plant and yield while fruit length showed numerical difference. With the exception
of fruit length, the other parameters did not show statistically significant differences although all data in 2004 were higher than those for 2006
numerically. It could be suggested that in the growing of pepino numerical differences in fruit diameter, fruit weight, fruit number per plant and
yield are affected by climatic factors.
Key words: Solanum muricatum, pepino, planting time, fruit quality, yield, climatic factors.
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Introduction
Pepino (Solanum muricatum Aiton) is a plant that is produced for
its fruits and belongs to the Solanaceae family. It is grown widely
in the north of South America and cultivated extensively in Chile1.
It has only very recently become known and cultivated in Turkey,
therefore, the amount of scientific study on this species is very
minimal in the country. Pepino, when grown in its natural
environment South America, is an evergreen plant that resembles
a small shrub which can produce fruits up to 15 cm in diameter.
These fruits are not only sweet and tasty but have an attractive
appearance with their purple stripes and yellow skin 1. Pepino is a
versatile fruit and can be consumed in different ways depending
on its maturity stage 2. The fruit is sweet and fragrant, high in
vitamins 3 with hypotensive and anti-tumour effects 4.
Mishqui (Solanum muricatum Aiton), also known as pepino, is
of interest as a crop for horticultural diversification in intensive
horticultural systems 5. Mishqui shows an impressive variation
for many characters of agronomic interest 6. This variation can be
exploited in order to select earlier clones. On the other hand, the
use of growing techniques that allow a reduction in the cycle
length also could contribute to an increase in earliness 5.
Pepino fruits have a very long growing period and also take 4 to
6 months to ripen 7. Several techniques are useful in improving
mishqui earliness. One of them is irrigation with saline water 5.
Others are auxin sprayings during fruit set 8, 9 and ethephone
applications 5. Other studies exist regarding fruit quality and
quantity. Morato et al. 10 have calculated parameters such as the
soluble content, yield, fruit number and fruit weight by applying
two different pruning methods to two pepino clones in hydroponic
culture. Kowalczyk and Kobryn 11 have measured the biological
values of pepinos that were grown in a greenhouse on rockwool
during two different ripening periods, spring-summer and autumn
cycles.
The purpose of this study was to reach information on yield and
some quality components of pepino (Solanum muricatum cv.
Miski) when grown under climatic condition in Kocaeli province
of Turkey. Since the cultivar has been recently given special
attention in the country, information on planting time is essential
in efficient breeding program for yield increase and to make
performance of the commercial cultivar higher. The effects of two
different planting months (April and May) in two different years
(2004 and 2006) on fruit diameter and fruit length as fruit quality,
as well as on total yield parameters such as fruit weight, amount
of fruits per plant and yield measures were studied.
Material and Methods
Experimental site: The experiments were performed in the same
field in the years 2004 and 2006 under Kocaeli University,
Arslanbey Campus, field conditions. Kocaeli province is in North-
Western part of Turkey. At the experimental area, the altitude was
100 m with location at latitude 40°46’N and longitude 29°56’E. In
that part of the country summers are hot and dry, winters are cold
and rainy. However, there are a lot of fields, orchards, glass-houses
and plastic tunnels where most of well-known annual summer or
winter vegetables, field crops and perennial fruits are grown like
in other parts of the country.
Soil analysis: In the first year, soil sampled at the depth of 0-30 cm
was analysed before fertilizer application and planting. The soil
included clay 76.34%, the pH was slightly alcalic at 7.4 and in
terms of salt soil was not salty with a rate of 0.058%. The CaCO3

552 Journal of Food, Agriculture & Environment, Vol.7 (2), April 2009
content was 0.97% and therefore the soil was slightly calciferous.
Organic material content 2.34% was at a medium level, nitrogen
content 0.117% at a good level, the P2O5 level 41.4 kg.ha-1 slightly
phosphoric and K2O level 247.6 kg ha-1 was low in potassium.
Meteorological conditions: Among meterological parameters, the
monthly minimum air temperature, monthly maximum air
temperature, monthly average temperature, monthly average
relative humidity and rainy days during the growing months (from
April to November) are shown in Table 1.
Plant material: The seedlings, used in the experiment were first
obtained during the January months of the aforementioned years,
full-grown pepino plants (Solanum muricatum cv. Miski) that were
recently begun to spread out commercially in Turkey. The cultivar
is herbaceous and has very branching habit with nearly woody
main stem. Fruits have attractive appearance with torpedo-like
semi-heart shape and cream-yellowish peel with dark-purple strips.
The seedlings were brought up in non-heated greenhouses. They
were 15 cm in length and these branch cuttings, which included 7-
8 nodes, were rooted under perlite. In March these rooted cuttings
were planted into seedling bags of 10 cm3 that contained a mixture
of perlite:turf:soil (1:1:1) and they were provided growing up in
the same greenhouse until transplanting of the seedlings.
Field preparation, fertilization and irrigation: Before planting
the seedlings, the field was first ploughed and in both years all
the parcels were equally fertilized at a ratio of 300 kg.ha-1 with 15-
15-15% N-P-K compound commercial granule fertilizer and finally
it was processed with cultivators in preparation for planting.
Seedlings that had 8-10 leaves were transplanted on April 27 and
May 27, 2004 followed by the 2004 experimentation and on April
25 and May 25, 2006 they were planted in the field followed by the
2006 experimentation. Experimental fields were irrigated once in
every three days with drip-irrigation system. Water was supplied
from a deep drilling in the area.
Plantation and experimental design: In both years the planting
times were one month apart. In this experiment, which was
performed in three replications according to the split-plot design,
the rows were separated by 1 m, and the plants by 50 cm within
the rows. In each sub-plot there were 36 plants, with 20 plants
excluded from the tests due to exposure to effects from the side,
so that the data were based on 16 plants per sub-plot. The fruits
that appeared ripe with cream-yellowish peel and purple stripes
were regularly harvested by hand in Monday in every week in
2004 between August 13 and November 19 for fifteen weeks and,
in 2006, between September 21 and October 12 for four weeks.
Fruit diameter and length were measured and recorded from
apparently the widest and the tallest part of all harvested samples
by using caliper-compass. The fruit number per plant was counted
with all samples. Yield was scaled with a scale for each sub-plot
weekly. All fruit samples measured and scaled were of commercial
appearance with no bruised and squashed parts.
Statistical analysis: Data were subjected to ANOVA analysis
(Minitab for Windows), sources of variation were fruit quality
and quantity parameters at two planting times in two years of
treatments. Mean comparisons were performed using Duncan’s
Multiple-Range Test to examine if differences of variables were
significant at p<0.05.
Results
Fruit diameter: As can be seen from Table 2, fruit diameter reached
its maximum and showed statistically difference with the April
2004 plantation at 6.91 cm/fruit, whereas May 2004, April 2006 and
May 2006 brought results which were similar to each
other. In terms of fruit diameter, there is not a
statistically significant difference by years.
Fruit length: The data did not vary in terms of planting
months but varied according to the year statistically,
and as a result the 2004 average in fruit length was
found to be superior, at 8.28 cm/fruit, to the average of
2006 (7.67 cm/fruit). Comparing the months, April 2004
plantation gave the best result numerically.
Experiment month Meteorological parameter Year
April May June July August September October November
2004 0.1 8.2 12.8 15.4 16.0 10.7 9.8 0.3 Minimum air temperature
(qC) 2006 4.2 8.6 13.0 15.0 16.5 14.5 9.1 1.5
2004 32.0 29.7 33.8 34.8 36.5 35.9 30.6 27.2
Maximum air temperature
(qC) 2006 29.4 34.4 37.1 32.8 38.7 30.8 29.0 23.1
2004 13.4 17.2 21.7 23.6 23.6 21.1 17.7 12.3
Average air temperature
(qC) 2006 13.4 17.9 22.1 23.6 26.5 20.3 16.9 10.6
2004 71.1 71.5 69.7 69.0 71.9 71.2 72.1 70.8
Relative
humidity (%) 2006 64.7 62.6 65.5 62.9 63.2 72.4 78.1 71.5
2004 6 8 13 3 9 5 7 11
Rainy days (days/month)
(above 0.1 mm ) 2006 6 5 11 2 2 14 13 9
Table 1. Meteorological parameters in growing seasons (from April to November) in 2004 and 2006*.
*The data were obtained from Republic of Turkey Ministry of Environment and Forestry, Turkish State Meteorological Service.
*Different lower-case letters within a column denote significant differences between the four months at p<0.05 and,
**Different capital within a column denotes significant differences between the two years at p<0.05 by Duncan test after
variance analysis using the Minitab for Windows Statistisc Program.
Year Planting
month
Diameter
(cm)
Length
(cm)
Weight
(g)
Fruit number
(fruits/plant)
Yield
(t ha
-1
)
April 6.91 a 8.51 268 a 7.08 a 36.52 a 2004
May 6.45 b 8.04 223 b 2.97 ab 14.03 ab
Average 6.68 8.28 A 246 5.03 25.28
April 6.09 b 7.58 164 c 2.12 ab 6.48 b
2006
May 6.37 b 7.76 200 bc 0.97 b 3.68 b
Average 6.23 7.67 B 182 1.55 5.08
Table 2. Effects of planting time on fruit quality, yield components and
yield in 2004 and 2006.

Journal of Food, Agriculture & Environment, Vol.7 (2), April 2009 55 3
Fruit weight: The result which is a yield indicator, did not vary
statistically based on the yearly averages, but April 2004 plantings
showed statistically significance with the heaviest weight at 268
g/fruit while the April 2006 plantings yielded the lowest weight at
164 g/fruit.
Number of fruits per plant: It was also statistically independent
of yearly averages, as the April 2004 planting gave the superior
result at 7.08 fruits/plant. The lowest result in this parameter was
obtained with the May 2006 planting (0.97 fruits/plant). The data
showed statistically significance of planting months on fruit
number per plant dependently planting months. The data verified
that early plantation has a great impact on fruit set in the two
years.
Yield: The yield in 2004 did not produce any statistically significant
results, yet on average it was found superior to the yield of 2006,
and statistically April 2004 plantings were the best at 36.52 t ha-1,
May 2004 results were second at 14.03 t ha-1, while 2006 April and
May plantings were last yielding 6.48 and 3.68 tha-1, respectively.
The results showed that early planting time gives the best yield in
both two years. In addition to the results, environmental condition
strictly affected yield in different years.
Comparing the years, even though there were no significant
differences, except for fruit length, the cultivation in the year 2004
was in every parameter superior to the average values of 2006
(Table 2). Taking yearly averages, the fruit diameter was 6.68 cm/
fruit in 2004 and 6.23 cm/fruit in 2006; fruit weight 246 g/fruit in
2004 and 182 g/fruit in 2006; number of fruits 5.03 fruits/plant in
2004 and 1.55 fruits/plant in 2006; while the yield in 2004 was
25.28 t ha-1 and 5.08 t.ha-1 in 2006. In terms of yearly averages the
year 2004 was numerically higher in every parameter.
Discussion
The topic of the experiment, that is, the fruit quality of the plants
planted at different times in the same field, in terms of fruit quality
parameters, yield and yield components, has not been tested before
in our condition, and therefore the discussion is carried out
considering experiments which are similar although not the same.
Accordingly, the planting times (April and May) are very
convenient for annual plants in summer in the city where the
experiment was performed. A study performed by Ercan and Ak²ll²12
in Antalya, the South of Turkey, on pepino plants in an open-area,
was run from April to August and concentrated on parthenocarpy,
implementing various hormone applications. This resulted in a
fruit weight in control fruits of 73.44 g/fruit. In our study, the
average weight ranged from 164-268 g/fruit.
The space distribution we used in our study, 2 plants m-2, is the
same as Welles 13 used in the Netherlands in a glass greenhouse
through January-July. In this study the ripening period of pepino
fruit was about 80-90 days and that he was able to obtain a
production of 9-10 kg m-2. In our study, the highest yield rate was
3.652 kg m-2 which was obtained in the April 2004 planting trial.
Morato et al. 10 performed two different pruning applications on
two pepino clones at two seasons, in a glass greenhouse in a
hydroponic system in rockwool, and the yield ranged from 2 to 4.8
kg/plant depending on the clones and the seasons in which they
were grown. In our study, this range was 0.184-1.82 kg/plant
depending on the treatment of the plants. The differences in
cultivating techniques should not be ignored.
In a study by Gonzales et al. 2, it was emphasized that samples
gathered for color and fruit composition at 3 different stages of
ripeness ranged from 181 to 330 g in commercial weights. In our
studies, the weight of the fruits ranged between 164 and 268 g on
average, ignoring the applications, and this result matches those
aforementioned.
According to a study carried out by Chen et al. 14 under
controlled conditions, NaCl salinity and carbon dioxide enrichment
on pepino in sand culture, the number of fruits varied between
0.75 and 5 fruits/plant depending on the applications. In our studies
this number varied between 0.97 and 7.08 fruits/plant, although
the treatments applied were different.
When the years are considered separately from other factors,
April 2004 planting showed numerical or statistical superiority
over the month of May 2004 in all parameters. In 2006, the April
planting was superior in terms of fruit number per plant and yield
but the May transplantation exceeded April’s in fruit diameter,
fruit length and fruit weight. In addition, when comparing the
avarage values of the two years, the year 2004 was superior in
every respect to the year 2006, although statistically only fruit
length could demonstrate this difference in parameters. This study
suggests that the growing of pepino depends on years and
consequently on climatic conditions.
Prohens et al. 15 showed that temperatures under 10°C and above
30°C are poor conditions for fruit formation, while BeÍirli and
Sürmeli 16 suggested that temperatures below 12°C and above
25°C affected yield negatively and low light intensity would hinder
the fruit from growing creme-yellow after ripening, decreasing the
amount of sugar content. In another study performed under
controlled glasshouse condition in our campus, air temperature
higher than 25°C caused negative effect on flower formation and
fruit set (unpublished data). Rodriguez-Burruezo et al.17 stated
that environmental factors play a large role in fruit quality, which
should be the main object of pepino cultivation programming.
Hewett 1 stated that problems in nutrition, warmth, light and
ripeness were to be solved and the best products would be
obtained under controlled conditions of cultivation. Kowalczyk
and Kobryn 18 performed a study using five pepino clones exposed
to two different light intensities of 70-75 and 200-250 µEm-2s-1
during two different day lenghts for 10 and 16 hours in a day, and
stated that the effect of the short day was observed in reduced
mass of fruit set in all the studied pepino clones.
In the light of all this data, in our experimental years during the
months of May and June, when the blossoms form that will
produce fruits capable of ripening, the highest temperatures in
2004 were 29.7 and 33.8°C; while in 2006 the highest temperatures
for those months were 34.4 and 37.1°C, respectively, significantly
higher than in 2004. This would suggest a negative effect on
flower formation and fruit yield. Nevertheless, during September,
the month when the pepino fruit, which enjoys heat while ripening,
truly matures, the maximum temperatures were 35.9°C in 2004 and
30.8°C in 2006, with 2006 thus showing a significant decrease.
This might indicate an interruption in ripening. Similarly, during
the ripening months, September and October, the number of rainy
days were 5 and 7, respectively, in 2004 and 14 and 13 in 2006. This
information suggests a decrease in light intensity with a
consequent negative effect on fruit maturity.

554 Journal of Food, Agriculture & Environment, Vol.7 (2), April 2009
Conclusions
Ultimately, pepino is a plant the growing of which depends on
years and consequently on climatic conditions, yet early
transplantation (following late spring frosts) might affect other
main quantity parameters such as fruits amount per plant and
yield. In our study, which ended with the first frosts of autumn,
we observed in both two years many fruits that could not complete
ripening although they remained on the plants after harvesting.
Therefore, this study was the first to explore cultivation seasons
in our region and it indicates the need for other experiments
(greenhouse cultivation, application of plant growth regulators,
watering with salt water, etc.) that encourage earliness and the
acceleration of ripening.
Acknowledgements
This research was supported by Scientific Research Committee of
Kocaeli University, Turkey. Project No:2004/25
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