The Effect of Climate (Temperature) on Potato Production
in Cyprus
AGWATER
Options for sustainable agricultural production and water use in Cyprus under global change
Scientific Report 3
Sophocles Gregoriou and Eleftherios Konstantis
Agricultural Research Institute, Nicosia, Cyprus
January 2014
Table of Contents
Introduction ................................................................................................................................. 2
Potato in the world ...................................................................................................................... 2
Potato in Cyprus .......................................................................................................................... 4
Swot Analysis of Cyprus Potato. ................................................................................................. 5
Effect of climatic conditions on potato ....................................................................................... 6
Plant growth ................................................................................................................................ 6
Material and methods ................................................................................................................. 8
Results - Conclusions .................................................................................................................. 9
Literature ................................................................................................................................... 15
1
The effect of climate (temperature) on potato production in Cyprus
Introduction
Agriculture in Cyprus is limited by highly variable climate conditions with precipitation being the
major constraining factor. The downward trend of precipitation and therefore rising water price are
setting new challenges. Potato crop as an irrigated crop is highly affected by these climatologically
trends and therefore sustainability of irrigation forms a challenge.
Aim of the project is to document and analyze available data in order to cover knowledge gaps and
develop a model in order to compute sustainable irrigation water supplies, agricultural water use,
crop yields and economic indicators.
In the current project data from long term trials on potato are exploited for the assessment of the
effect of climate (temperature) on the production of this highly important crop.
Potato in the world
The potato was first domesticated in the high Andes of South America around Lake Titicaca over a
thousand years ago. Brought by the Spanish conquistadors from Peru to Europe in the mid-16th
century, the potato was first grown as an exotic tropical plant and thought to have mysterious
medicinal properties. Only some two centuries later, did the potato became part of the regular diet
in Europe (FAO, 1995).
Potato was brought to Europe on two occasions, to Spain in 1570 and to England between 1588
and 1593 (Hawkes, 1967). From these two introductions, potatoes were spread into nearly every
part of the world (Hawkes, 1978a).
The most important cultivated potatoes belong to the species, Solanum tuberosum L., 2n=4x=48.
In addition to S. tuberosum some seven other cultivated species and over 160 wild species of
potato, which may be diploids, triploids or pentaploids with somatic chromosome numbers 2n=24,
36, or 60, respectively, are generally recognized (Hawkes, 1978b).
Potato is one of the most important crops worldwide and its importance is increasing as population
of world increases. Correlation of grain crops with oil price underlines the importance of the crop
2
on food security. A remarkable fact about potato is its high yield per unit area, which benefits the
crop against the fight for land due to the “war” between food and bio-fuels.
Potato is the most important vegetable crop, and ranks in fourth place among the most important
food crops, after wheat, rice and maize (FAOSTAT, 2010). Total production represents roughly half
of the world’s annual output of all roots and tubers. The crop is eaten by over one billion people
worldwide and is part of the diet of half a billion consumers in developing countries (FAO, 1995).
Every year 207 millions tones of potatoes are consumed worldwide, fact which places potato crop
in the third place of world’s most consumable crops, after rice and wheat, which have annual
consumptions of 511 and 421 million tons respectively.
World production of potato has increased relatively fast due to the production from developing
countries. One third of the world production belongs to developing countries and especially to Asia
region. High yield, short cultivation period and nutritional characteristics are mainly the reasons for
the selection of potato crop from these countries. These characteristics set potato crop as the top
one for production of edible energy per time per unit area.
Potatoes are produced in over 130 countries, and their consumption is steadily increasing in the
two most rapidly developing countries, China and India. The annual per capita potato consumption
in the world averages 28kg. Demand for fresh potatoes as food is falling in the developed countries
but increasing in the developing countries. Over time, the declining trend in the per capita intake of
table potatoes is partially offset by the increasing per capita consumption of processed products
(Walker et al., 1999; FAO, 1995).
Currently, China is the leading potato producer, while India follows with production equalling with
half of China (FAOSTAT, 2010). The population of China is estimated to increase continuously
until it reaches 1.5 billion. Chinas target for 95% food self-sufficiency equals to an annual increase
of 100,000,000 tons. of which 50% is expected to be potato production.
Potato is grown in different climatological zones, including temperate regions, the subtropics and
tropics, under very different agro-ecological conditions, lowlands as well as highlands, and in very
different socio-economic environments, by large-scale farmers in high external-input agriculture
business as well as by small holders in developing countries (Struik and Wiersema, 1999).
3
In the countries surrounding the Mediterranean sea the potato is a crop of great significance. Due
to favorable climatic conditions, it can be cultivated throughout the year where planting and
harvesting dates depend on the specific area of cultivation. The Mediterranean region differs from
Northern Europe not only in its environmental conditions but also in the different use of high
technology and adaptation of potato cultivars. A great problem related to potato cultivation in the
Mediterranean area is the availability of seed tubers at the right physiological stage (Frusciante
and Ranalli, 1999).
Potato in Cyprus
Potato is considered as the most important vegetable crop in Cyprus, grown across a total area of
4500 ha annually. The total annual value of exports exceeds the value of 30 million Euro,
representing about 40% of all agricultural exports. The annual production of ware potatoes ranges
from 100-120 thousand metric tons. More than 75% is exported, mainly to countries of the
European Union (U.K. and Germany).
Potatoes are cultivated throughout most of the year in Cyprus with the bulk of the spring crop
produced between March and June from plantings during November to January. Smaller quantities
of early potatoes are exported during January/February (intermediate crop) from plantings in
September/October. A third crop (winter crop) from plantings in August/September harvested in
November/December is mainly exported during the Christmas period or is used for local
consumption (Gregoriou and Onoufriou, 2001). The potato seed is mainly imported from Europe.
The quantity of the imported seed and the seed produced locally was 8400 and 2000 tons
respectively (Agricultural Statistics, 2010). The seed produced locally is obtained by the
multiplication for only one year of imported elite seed (Vakis, 1980).
In Cyprus about one fifth of the seed planted in autumn and spring crops is produced locally. Until
now it appears that under Cyprus conditions the best approach to produce part of the requirements
of seed potatoes is a single multiplication of imported stocks (certified or foundation seed). Locally
produced seed perform equally satisfactorily as imported seed. Ware crops grown from local seed
were as healthy as crops grown from imported seed (Vakis, 1980). The physiological stage of local
seed at planting time appears to be such as to allow the production of early crops with satisfactory
yield. Further research work for the production of healthy potato seed through the use of
micropropagation was carried out by the Agricultural Research Institute (Gregoriou, 2009). A
complete system from the laboratory to the production of certified seed in the field was developed.
4
Swot Analysis of Cyprus Potato.
The strengths, weakness, opportunities and threads of the potato crop are summarized below:
Strengths

The mild Mediterranean climate of Cyprus is of its strengths in the production and marketing of
high-quality early potatoes in European and international market.

Climate allows for more than one crops per year

The good infrastructure in human, technological and plant capital, both in scientific research
and support in the sector, and the production and marketing of potatoes, are strong elements.

Powerful element is, of course, the advanced infrastructure in water management and
sufficient irrigation of crops.

The reputation of the Cyprus Potato in the markets abroad as a product with excellent quality.

More than 50% of potatoes exported to overseas markets are certified that have been
produced based on the principles of Integrated Production Management (GlobalGap, etc.)
Weaknesses

The small size and fragmentation of farm units, lead to increased cost and reduced
competitiveness of potatoes.

The limited rainfall and lack of sufficient quantities of water.

Organizations and marketing structures of potatoes need further strengthening and
modernization.

The distance from overseas markets which result in high transportation cost
Opportunities

The registration of Cyprus potatoes as a product of Products of Origin or Products of
geographical Indication

The production of certified organic potatoes will significantly broaden their horizons and
marketing profitability of the Cypriot potatoes.

The possibility of producing seed potato, both for local usage, as well for exports.
Threats

Competitive pressures on Cyprus early potatoes from other Mediterranean Member countries
of the EU to EU markets and other international markets .
5

Competitive pressures on Cypriot potatoes exports from other Mediterranean countries, which
enjoy preferential treatment from the EU, eg Egypt and Israel.

Competitive pressures on Cyprus potatoes from EU-5 countries (U.K., the Netherlands,
Belgium, Germany and northern France).

Possible intensification of climate change and any reduction in rainfall patterns will have
serious negative implications for the Cypriot potato growers.

The intense competition between traders of Cyprus potatoes to foreign markets
Effect of climatic conditions on potato
In general, potato thrives in cool climate conditions. Best yields are founded at areas where
temperature during cultivation period is even, without fluctuations and with moderate to frequent
rainfalls (Patsalos, 2005).
High temperatures of 26-28 °C, or more, favor the foliage development and conversely, low
temperatures of 15-18 °C combined with ample light and high humidity favor the tuber growth.
Relatively low temperatures are appropriate as well for sprout growth. At temperatures of 12-13 °C,
emergence is achieved within 12-30 days.
Potato plant is sensitive at very low temperatures. At temperature of 3 °C serious damage is
caused to the foliage and at temperature below minus 2 °C, plants will entirely freeze and
destroyed (Patsalos, 2005).
Planting seasons are determined by the climate of the area. According to climate and season,
cultivation areas can discerned in two categories: (1) low temperature and (2) high temperature. At
low temperature regions usually only one crop per year is possible and the duration of season is
determinate by the minimum temperature requirements for growth and frost avoidance. In contrast,
at high temperature region until three crops can be grown.
Plant growth
The process of the development and the formation of both stolons and tubers is strongly influenced
by climatic factors such as photoperiod and temperature. The growth and development of potato
plants can be divided into several genetically and environmentally controlled growth stages.
Knowledge of these stages is required for scientists as well as farmers (Kolbe and StephanBeckmann, 1997). Milthorpe (1963) divided the time between planting to the time of harvest of
potato in the field into three periods: the pre-emergence stage, the haulm stage and the tuber
growth stage. The phases of haulm growth and tuber growth are closely interrelated and
overlapping. Kolbe and Stephan-Beckmann (1997) describe the two-digit scale of Hack et al.
(1993, in Kolbe and Stephan-Beckmann, 1997), which includes 10 stages of growth and
development in relative scales from 00 (dormant seed tuber) to 99 (harvested tubers). The storage
phase extends from lifting until the tubers are planted some months later.
The pre-emergence phase involves the establishment of root and leaf surfaces from materials
stored within the mother tuber, and occurs at a rate determined mainly from the soil temperature
and the size of sprout at planting (Milthorpe, 1963; Firman et al., 1992). Rate of sprout elongation
6
increases with the temperature over the range 4-20 °C but there is usually a lag phase before
linear growth occurs (Firman et al., 1992). Rate of emergence is slower in dry soil, and especially
so at high temperatures. Prolonged intervals from planting to emergence in low soil temperatures
frequently lead to shorter stems and lower leaf area (Allen et al., 1992). Planting old seed in cold
soil can possibly cause tuberization before emergence (Moorby, 1978). Throughout the period of
emergence growth the plant is dependent on the carbohydrate reserves of the mother tuber. After
emergence leaf expansion is rapid because most of the primordia, which expand into leaves, are
already present in the shoot apex. The plant rapidly becomes autotrophic, usually by the time 200400 cm² of leaf have been produced (Headford, 1962) but the transfer of reserves from the mother
tuber continues until the latter is almost completely depleted or until microbial infection brings
about decay. Throughout this period there is a net loss of dry weight from the mother tuber.
These is, however, a continual turnover of materials and it is possible to demonstrate the
incorporation of photosynthetically incorporated 14 C into ethanol-insoluble reserves in the mother
tuber at a time when the latter has lost 80% of its original dry weight (Moorby, 1968).
Gregory (1956) found, using cv Kennebec, that tuber yield was good if plants were grown in short
days (SD) with low night temperature, but no tubers were formed in SD with high night
temperature. Menzel (1980) found that the effects of high temperature could be reversed by (2 –
chloroethyl) – trimethylammonium chloride (CCC). Menzel (1980, 1985) considers that both high
temperatures and low irradiance exert their effects by the production of a growth substance,
possibly gibberellin. High temperatures decrease partitioning to tubers, and favour haulm growth
(Ewing, 1981). Went (1959) showed that temperature affected not only the yield of the treated
plants, but also that of their progeny.
Tuber formation may be regulated by the relative activity of several substances rather than the
absolute concentration of a single substance (Slater, 1968; Hammes and Nel, 1975), and the
substances may be involve in the tuber formation stimulus (Okazawa and Chapman, 1962) which
is yet unidentified.
It is evident that tuber initiation is hastened in short days and low temperatures although the
response varies with variety and species. There have been two suggestions concerning the nature
of responses of the plants which are thought to be due either to the presence of some tuberization
stimuli (Madec, 1963) or to the difference in substrate supply to the stolon tips as a consequence
of growth differences in the haulms (Slater, 1963).
7
Material and methods
For the current project, data from long term potato experiments carried out by the Agricultural
Research Institute during the period 1975 to 2010 were analyzed. In this period 520 varieties and
412 clones were evaluated. For the needs of the project, the varieties Cara, Nicola and Spunta
were used. These three varieties are considered of significant economic importance. .Spunta is a
very early variety with long tubers suitable for fresh consumption. Nicola is a salad variety with
long-oval tubers and medium maturity. Cara is a late variety with round tuber, suitable for bakers
and exported mainly in the Scandinavian countries
Data were correlated to meteorological data provided by the Cyprus Meteorological Service for the
period 1970-2012. Data were obtained from meteorological station 731, nearby Larnaca airport.
Even though there are other stations closest to Xylophagou Larnaca’s station was chosen because
is the only one to provide consistence data for the period of the collected data. As mean average
temperature was calculated the temperatures from December to May, representing the growing
period of the spring crop, which is the main growing season for potatoes All the meteorological
data were received from the Meteorological Service.
Location
All the trials were carried out at Kokkinochoria, the main potato growing area of Cyprus. All trials
were set up in the same area, at Xylophagou village. The red soil of the area (Terra rosa), which
sticks to the tuber, and the high tuber quality characterize Cyprus potatoes in the foreign markets.
Cultivation Period
Trials were carried out for the spring crop. Planting took place at late December-early January
while harvesting at late April early May, according to the climatic circumstances of each year. The
cultivation period of the trials averages at four months.
Cultivation Practices
The Randomized Complete Block Design with 2-4 replications was used for all experiments. The
plot size was either 2.6 x 2.4 m or 2.6 x 4.8 m comprising four rows of 12 or 24 plants each. Data
were collected only from the two middle rows; the other two rows were used as guard rows and for
observation purposes during the growing period. The varieties Spunta, Cara and Nicola were used
in most experiments as controls.
Planting distance was 65 cm between rows and 20 cm within rows. Compound fertilizers (14-22-9
or 20-20-10) at the rate of 1500 kg/ha were applied at planting. Supplemental top dressing fertilizer
was applied during February.
Irrigation was applied by mini-sprinklers; depending on weather conditions, there were 6 to 10
irrigations during the growing period. Good quality dam water was used for irrigation. The total
water requirements of the spring crop ranges between 3500 m3 - 4000m3 per hectare.
Weed control was managed with herbicides and also mechanically between the lines during the
earthing up at about 60 days from planting.
8
Results - Conclusions
As far as it concern climatic change, precipitation and temperature are the two main variables that
can affect the crop yield. Since potato is an irrigated crop in Cyprus no conclusions can be made
on any fluctuations of precipitation in comparison with yield. Therefore conclusions are focused on
the effect of temperature.
Ficure 1 presents the annual average temperature for the period 1976-2012 at the area of
Larnaca. There is a continuous slight increase of the temperature from 1976 and thereafter.
Extreme low temperatures were recorded in the year 1982/1983 and the period 1991-1993.
Extreme higher temperatures above the average were recorded after 1995 up to 2010. These were
the periods 1993/1994, 1998/1999, 2000/2001and 2009/2010.
The relationship between the temperature and the time is expressed by the equation:
Temperature = 14.26+0.0421* year
The model as fitted explains 29.1% of the variability in temperature and there is a statistically
significant relationship between the temperature and the year at the 95% confidence level.
The yields of the experimental plots of the Agricultural Research Institute were compared to the
total production of potatoes in Cyprus from the FAO Statistics (Figure 2). Although the lines of the
production are moving in different levels, 40-70 and 10-30 t/ha for the Agricultural Research
Institute and FAO, respectively, the main characteristics of the lines are almost identical. Severe
decrease of the yield was recorded in the years 1980, 1985, 1994, 1997 and 2010. The differences
in the lines as regard their slope and the yield can be explained from the fact that the results from
the Agricultural Research Institute are obtained from small experimental plots in the Xylophagou
area while that of FAO are values covering all the island.
During spring 1985, weather conditions were abnormal in relation to potato growing (Vakis, 1985).
Two severe frosts in February damaged most of the potato plantations. Due to low temperatures
emergence, growth development and lifting were delayed. The low temperature in 1992 especially
after planting (Myrianthousis, 1992) resulted in delay for emergence and lifting. On the other hand
the weather conditions in 1993 from planting to lifting were favorable and yield were above
average (Gregoriou, 1993).
In 1994 although the weather conditions during the growing period were favorable for potato
growing, the yields obtained were at least 25% lower than the normal. This was due to heavy
infection by the leaf miner Lyriomyza huidobrensis (Gregoriou, 1994).
In 1997 the weather conditions for the growth of potatoes were the worst since the beginning of the
century. Temperatures following the second half of December and until the middle of January,
were very favorable for potato growth. Early varieties by the middle of December emerged in less
than 30 days. In the last week of January, temperatures fell gradually and by the beginning of
February, frost (one week) completely destroyed the plant canopy. During plant recovery frosts
came in waves from the last week of February until the 10th of April and the plants were severely
damaged (Gregoriou and Onoufriou, 1997).
9
The decrease in yield in 2000 and 2010 is also caused by night frost. In 2010 the damages were
the result of a heavy frost for only a night, but with duration of five hours (Gregoriou and
Kourtellarides, 2010)
Form the above description is concluded that the most risk factor for the development and the
production of potatoes are weather conditions and especially the frost. Hail, freezing wind, heavy
rains are not negligible and sometimes they cause severe damages, locally. According to weather
conditions, pest and diseases are very often responsible for heavy losses. Phytophthora infestans
is the main pathogen for the potato crop.
The reaction of the varieties Spunta, Nicola and Cara is almost identical on the chronological
period (Figure 3). In a comparison test of the three regression lines there is a statistically
significant relationship between variables (year and yield) at the 95% confidence level.(Figure 4)
but there are no statistically significant differences among the intercepts and slopes for the various
values of variety at the 90% or higher confidence value.
Comparing the yield of the three varieties in relation to the mean temperature of each year
(Figure 5) there is not statistically significant relationship between the variables at the 95% or
higher confidence level and no statistically significant differences were found among the intercepts
and the slopes for the various values of variety at the 090% or higher confidence level.
10
17
Temperature °C
16
15
y = 0.0421x + 14.262
R² = 0.2906
14
13
Year
Figure 1.
Average temperature for the period 1976-2010 at the area of Larnaca Airport
(Meteorological station 731).
90.0
80.0
70.0
Yield (t/ha)
60.0
50.0
ARI
40.0
FAO
30.0
20.0
10.0
0.0
1975
1980
1985
1990
1995
2000
2005
2010
Year
Figure 2.
Yield from the experimental plots of the Agricultural Research Institute (variety Spunta)
and FAO Statistics.
11
1979
1980
1981
1982
1983
1984
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2012
Yield (t/ha)
10.0
30.0
20.0
2012
2006
2005
2004
20.0
2003
30.0
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
1988
1981
1976
Yield (t/ha)
1973
1974
1975
1976
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2012
Yield (t/ha)
90.0
80.0
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
y = 0.7747x + 40.911
R² = 0.3424
A
Year
90.0
80.0
70.0
60.0
50.0
40.0
y = 0.9182x + 43.945
R² = 0.2398
10.0
0.0
Year
90.0
80.0
70.0
60.0
50.0
40.0
y = 0.825x + 40.199
R² = 0.3449
C
0.0
Year
Figure 3. Yield of varieties Spunta (A), Nicola (B) and Cara (C) during the tested period.
12
80
Variety
Spunta
Nicola
Cara
Yield (t/ha)
60
40
20
0
1970
1980
1990
Year
2000
2010
Figure 4.Comparison of regression lines of yield of the varieties Spunta, Nicola and Cara in relation
to the year of growing.
80
Variety
Spunta
Nicola
Cara
Yield (t/ha)
60
40
20
0
13
14
15
Temperature °C
16
17
Figure 5. Comparison of regression lines of yield of the varieties Spunta, Nicola and Cara in
relation to the mean temperature
13
Potatoes are grown under a wide range of daylength regimes from 12 hours of sunlight in the
Andes and equatorial zones of Africa and Asia to over 16 hours of sunlight in Alaska and Chile
(Horton, 1987). Daylength and temperature can influence the growth habit of the potato in
unexpected ways. Short days and moderate temperatures, particularly low night temperatures,
stimulate tuber initiation.
High daytime temperature is usually correlated with a high rate of respiration, which may cause
plant moisture stress even when the soil moisture content is high. Furthermore the rate of net
photosynthesis decreases when temperatures are higher than about 25 degrees C. Minimum
nighttime temperature is also a critical variable. As a rule, tubers will not begin to form if night
temperatures remain above 20 degrees C. High night temperatures increase plant respiration,
depleting carbohydrates reserves and slowing tuber temperature. Soil temperatures below about
12 degrees or above 28 degrees C impair sprout development (Horton, 1987).
In recent years mathematical models were developed to describe the growth of the potatoes
(MacKerron, 2008). Characteristics of crop and models that must be reconciled are: the crop data
and cultivar characteristics, soil data and soil conditions, growth of the crop and weather data.
MacKerron et al. (2004) presented the MAPP (Management Advisory Package for Potato) a model
that set out factors and variables those influence the states of development of the crop. As a
decision support system is giving informed options not making decisions.
It is concluded from ARI experiments in potatoes in the period from 1975 to 2012 that extreme
weather conditions, mainly frost, reduce the possibility of a normal production. There was an
increase in the yield during the years but this was not an effect of the mean year temperature. On
long term basis the varieties examined had no statistical effect on the yield.
14
Literature
Agricultural Statistics, 2010. Statistical service, Republic of Cyprus, Nicosia.
Allen, E.J., O´ Brien, P.J. and Firman, D., 1992. Seed tuber production and management. In: Harris,
P.M. (Ed.). The Potato Crop. The scientific basis for improvement. Second edition, Chapman
and Hall, London, pp. 247-292.
Ewing, E.E., 1981. Heat stress and the tuberization stimulus. Am. Potato J., 58: 31-49.
FAO, 1995. Potatoes in the 1990s: Situation and prospects of the world potato economy.
International Potato Center and FAO. Rome: FAO.
FAO Stat, 2010. http://faostat.fao.org.
Firman, D.M., O'Brien, P.J. and Allen E.J., 1992. Predicting the emergence of potato sprouts. J.
Agric. Sci., Camb., 118: 55-61.
Frusciante, L. and Ranalli, P., 1999. Breeding and physiological aspects of potato cultivation in the
Mediterranean region. Abstracts of Conference Papers, Posters and Demonstrations. 14th
Triennial Conference of the European Association for Potato Research, Sorrento, Italy, pp. 710.
Gregoriou, C., 1993. Progress report on the evaluation of potato varieties and clones (spring crop).
Agricultural Research Institute, Nicosia, 22p
Gregoriou, C., 1994. Progress report on the evaluation of potato varieties and clones (spring crop).
Agricultural Research Institute, Nicosia, 28p
Gregoriou, S., 2009. Intensive Potato Seed production. Agricultural Research Institute, Nicosia (in
Greek).
Gregoriou, S. and Kourtellarides, D., 2010. Progress report on the evaluation of potato varieties
and clones (spring crop). Agricultural Research Institute, Nicosia, 14p
Gregoriou, S. and Onoufriou, N., 1997. Progress report on the evaluation of potato varieties and
clones (spring crop). Agricultural Research Institute, Nicosia, 24p.
Gregoriou, S. and Onoufriou, N., 2001. Progress report on the evaluation of potato varieties and
clones (spring crop 2001). Agricultural Research Institute, Nicosia, 27p.
Gregory, L.E., 1956. Some factors for tuberization in the potato plant. Am. J. Bot., 43: 281-288.
Hammes, P.S. and Nel, P.C., 1975. Control mechanisms in the tuberization process. Potato
Research 18: 262-272.
Hawkes, G.J., 1967. The history of the potato. J. Roy.Hort. Soc., 92:207-224, 249-262, 288-302,
364-365.
Hawkes, G.J., 1978a. The history of the potato. In: Harris, P.M., (Ed.). The Potato Crop. The
scientific basis for improvement. Chapman and Hall, London, pp. 1-14.
Hawkes, G.J., 1978b. Biosystematics of the potato. In: Harris, P.M., (Ed.). The Potato Crop. The
scientific basis for improvement. Chapman and Hall, London, pp. 15-69.
15
Horton, D.,1987. Potatoes, production, marketing and programs for developing countries. IT
Publications, London.
Headford, D.W.R., 1962. Sprout development and subsequent plant growth. Eur.Potato. J., 5: 14-22.
Kolbe, H. and Stephan-Beckman S., 1997. Development, growth and chemical composition of the
potato crop (Solanum tuberosum L.). I. Leaf and stem. Potato Research 40: 111-129.
MacKerron, D.K.L., Marshall, B. And McNicol, J.W., 2004. MAPP, the Management Advisory
Package for Potatoes: decition support means giving informed options not making decisions.
In: MacKerron, C and Haverkort, A.(Eds). Decision support systems in potato production. pp
119-141.
MacKerron, D.K.L., 2008. Advances in modelling the potato crop: sufficiency and accuracy
considering users, data and errors. In:Chirou, S., Olteanu, G., Altea, C. And Badarau, C.,
(Eds.). Potato for a changing world. Abstracts of papers and Posters, 17th Triennial
Conference of the European Assosiation for Potato Research University of Brasov Publishing
House , Brasov, pp 47-49.
Madec, P., 1963. Tuber forming substance in the potato. In: Ivins, J.D. and Milthorbe, F.L., (Eds.).
The growth of potato. Butterworths, London.
Menzel, C.M., 1980. Tuberization in potato at high temperatures: interaction gibberellin and growth
inhibitors. Ann Bot., 46: 259-265.
Menzel, C.M., 1985. Tuberization in potato at high temperatures: interaction gibberellin and
irradiance. Ann Bot., 55: 35-39.
Myrianthousis, T., 1992. Progress report on the evaluation of potato varieties and clones (spring
crop 2001). Agricultural Research Institute, Nicosia, 22p
Milthorpe, F.L., 1963. Some aspects of plant growth. In: Ivins, J.D. and Milthorbe, F.L., (Eds.). The
growth of potato. Butterworths, London, pp. 3-16.
Moorby, J., 1968. The influence of carbohydrate and mineral nutrient supply on the growth of potato
tubers. Ann. Bot. 32:57-68.
Moorby, J. 1978. The physiology of growth and tuber yield. In: Harris, P.M. (Ed.) The Potato Crop.
The scientific basis for improvement. Chapman and Hall, London, pp. 153-194.
Okazawa, Y. and Chapman, H.W., 1962. Regulation of tuber formation in the potato plant. Physiol.
Plant., 15: 413-419.
Patsalos, K., 2005. The cultivation of Potato. Department of Agriculture, Edition 9/2005,
Nicosia Cyprus.
Slater, J.W., 1963. Mechanism of tuber initiation. In: Ivins, J.D. and Milthorbe, F.L., (Eds.). The
growth of potato. Butterworths, London.
Slater, J.W., 1968. The effect of night temperature on tuber initiation of the potato. Eur. Potato J., 11:
14-22.
Struik, P.C. and Wiersema, S.G., 1999. Seed potato technology. Wageningen Press, Wageningen.
16
Vakis, N.J., 1980. Production of seed potatoes in Cyprus. Technical Bulletin 34. Agricultural
Research Institute, Nicosia, 12p.
Vakis, N.J.,1985. Progress report on the evaluation of potato varieties and clones (spring crop 2001).
Agricultural Research Institute, Nicosia, 26p.
Walker, T.S., Schmiediche P.E. and Hijmans R.J., 1999. World trends and patterns in the potato
crop. An economic and geographic survey. Abstracts of Conference Papers, Posters and
Demonstrations. 14th Triennial Conference of the European Association for Potato Research,
Sorrento, Italy, pp. 3-5.
Went, F.W., 1959. Effects of environment of parent and grandparent generations on tuber production
by potatoes. Am. J. Bot., 46: 277-282.
17