沙漠研究 19-1, 213- 216 (2009 )Journal of Arid Land Studies“Desert Technology IX ”
Refereed Paper

Study of the Variability between Local Melon Cultivars in Tunisia-Based on the Content of Mineral Elements in LeavesRim LAMARI1, Leila LAARAYEDH1, Mokhtar ELBEKKEY1, Tebra TRIKI1, Leila BENYAHIA1, Ali FERCHICHI1
Abstract: The levels of 3 mineral elements in leaves, sodium (Na+), potassium (K +) andphosphorus (P) were used to conduct a study of biodiversity between 24 local landraces and 3
reference varieties of melon in Tunisia.
The potassium mineral fraction is the most important since its content can reach 2% of dry
weight of leaves while phosphorus is the minor fraction as does not exceed 0.313% of dry
weight of leaves.
The analysis of variance allowed the mineral elements to be separated into two categories.
The first category includes sodium and potassium and showed a significant difference between
cultivars. The second category, which includes the phosphorus content does not show
variability between cultivars and therefore is not an appropriate setting for the study of
biodiversity.
The dendrogram obtained by combining the three factors gave three distinct groups; thisclassification reveals an affinity between some cultivars and commercial varieties on thecontent of mineral elements.
Keywords: Analysis of variance (ANOVA), Melon, Variability, Mineral elements in leaves(Na+, K+, P)

1. Introduction
Melon (Cucumis melo L 2n =2x =24) whose origin is thought to be Africa (Robinson andDecker-Walters, 1997) belongs to the cucurbitaceae (Kikbride, 1993). Melon is an important horticultural
crop often cultivated in arid and semiarid regions of the world where salinity threatens to become, oralready is, a problem (Navarro et al., 1999).
The level of salts in most irrigation waters is below the threshold for the more sensitive crops, salt
accumulation in irrigated soils from both irrigation and groundwater sources can increase salinity to level
which can reduce growth and yield of even the more tolerant crops. Overcoming salt stress is a main
issue in these regions to ensure agricultural sustainability and continued food production (Heuer, 2003).
Sodium is the predominant soluble cation in many of the soils of arid and semi arid areas. However
most plants, especially glycophytes, are very sensitive to high Na+ concentrations. The ability of plant
cells to maintain sodium concentrations low in the cystol is a vital process associated with the ability of theplant to grow under high salt regimes (Blunowold, 2000; Ashraf and Harris, 2004).
Potassium is a major plant macro-nutrient that plays important roles related to stomatal behavior,osmoregulation, enzyme activity, cell expansion, neutralization of nondiffusible negatively charged ionsand membrane polarization (Maathuis and Sanders, 1996; Elumalai et al., 2002).
2. Materials and Methods
The seeds of twenty-four landraces of melon, collected from farmers in Tunisia (Table 1) andharvested in a field were used to provide the plant material for all studies. In addition to these local
landraces of melon, we chose three commercial varieties that will serve as a reference. Data related tothese cultivars are summarized in Table 1. The melon leaves are collected and dried in the oven for 48
hours at a temperature of 60 ˚C and then they are crushed (powdered). From each sample, 1 g inporcelain crucibles, were placed for 5 h in a muffle furnace set to a temperature of 550 ˚C. Once cooled,samples were exposed to 1 ml of hydrochloric acid and 4 ml of distilled water. Samples were thenbrought to boil after being placed on a hot plate and filtered twice in a flask.
Finally, the volume was brought to 100 ml and this solution served as the extract for the analysis ofsodium, phosphorus and potassium. The concentration of potassium and sodium was determined using a1Arid Areas Institute of Tunisia, laboratory of arid and oasis cropping
Tel. no. +216 75 633 005, fax. no. +216 75 633 006. E-mail: ramroumam@yahoo.fr

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Table 1. Code, date and locality of collection of cultivars.
Cultivar

Locality

Cultivar

Locality

M3

Lbness Elgataya kebili

M50

Eljazira, Souk lahad

M5

Isteftimi Kebili

M58

Gannouche, Gabes

M6

Hniche Douze

M61

Bir Amir, Tataouine

M9

Elrabta Kebili

M95

Ben Guerdane, Medenine

M15

Elrabta Kebili

M97

Oum Elsoumaa, Souk Lahad

M16

Elrabta Kebili

M116

Azmour, Dar Allouch, Nabeul

M17

Elrabta Kebili

M120

Kalaat Elandalouss, Bizerte

M18

Elmenchia, Souk Lahad

M122

Ghar El Melh, Bizerte

M19

Elmenchia, Souk Lahad

M125

Hammet Tozeur

M20

Rabta, Kebili

M131

Elrabta Kebili

M24

Dgache Tozeur

Yellow canari

JC

M26

Elmenchia Souk Lahad

Lobnani

LOB

M29

Rogba Tataouine

MaazounMaz

M31

Ferche Tataouine

flame photometer while the phosphorus was determined using a spectrophotometer.
The data from all parameters were statistically analyzed by one way ANOVA, and means wereseparated by Duncan’s Multiple Range Test using SPSS software. Finally, a dendrogram was obtained bycosine interval using the same software.
3. Results and Discussion
The analysis of variance showed that the mineral elements studied can be classified into twocategories;
Minerals in the first category are sodium (Na+) and potassium (K+) showing significant difference (p= 0.002 and 0.031 <0.05 respectively), these factors are distinguishing parameters between the cultivars.
The second category contains phosphorus where the average between cultivars do not show variability(p=0.073> 0.05), so this parameter is not an appropriate setting for the study of polymorphism. Forsodium (Na+) and potassium (K+), Duncan’s test identified five groups while for phosphorus only three.
Phosphorus represents the minor mineral fraction in leaves of melon as its maximum does not exceed
1.233% of dry weight for the cultivar M18 (Fig. 1). The cultivar with the minimum content is M24(content equal to 0.138% of dry weight).
1,400

3,000

d
1,200ed

2,500

dd

1,000

2,000

a0,800ccc

1,500
0,600

b
0,400

0,200

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1,000

Fig. 1. Average of phosphorus content in leaves ofdifferent melon landraces.

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0,500

0,000
J M
M M M M M M M M M M M M M M M M M M M M M M M M L C
A
3 5 6 9 1 1 1 1 1 2 2 2 2 3 5 5 6 9 9 1 1 1 1 1 O
5 6 7 8 9 0 4 6 9 1 0 8 1 5 7 1 2 2 2 3 BZ
6 0 2 5 1acc

M M M M M M M M M M M M M M M M M M M M M M M M L JC M
O
3 5 6 9 1A5 1
6 1
7 1
8 1
9 20 24 2
6 2
9 3
1 50 58 61 95 97 1
1 12 1
2 1
2 1
3 B
Z
6 0 2 5 1

Fig. 2. Average of potassium content in leaves ofdifferent melon landraces.

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The potassium mineral fraction is the most important and its share can reach up 2% of dry weight for thecultivar M116, its minimum is about 0.704% of dry weight in the variety M9 (Fig. 2).
The sodium content varies widely among different cultivars; it ranges from 0.174% of dry weight for thevariety Maâzoun to 1.03% of dry weight for M6 (Fig. 3).
The differences between cultivars are not related to differences in the availability of mineral elements atground level as the culture has been installed on the same plot.
When compared with those recorded by Sivritepe et al. (2005) on a control culture, the sodium content
for different cultivars are considered high, this may be due to salinity in the irrigation water (2 g/l), or at
ground level (2 dS/cm). The sodium content in leaves can learn about the plants more tolerant to salt stresssince, according to Sebnem et al. (2007), the plants more tolerant to salt stress are those with low content ofNa+ in leaves in the same context Jones and Gorham (1989) reported that the plants more tolerant to stress arethose with an important ratio of K+/Na+, all varieties have an important ratio of K+/Na+.
However other studies suggest that generally the most salt tolerant plants accumulate Na+ in their shoots
whereas sensitive plants don’t. In the first type, called "Includers", salt was trapped and accumulated in theaerial organs cells, mainly in its vacuoles (Levigneron et al., 1995; Yeo and Flowers, 1986).
In the second type, referred to as “excluder” the salt conveyed to the shoots, fault to be trapped, wasre-exported towards the roots by the phloemic tissue (Fortmeir and Schubert, 1995; Lessani and Marschnner,1978; Slama, 1982; Wieneke and Laüchli, 1980).
This accumulation was associated with a water content stability. Such a mechanism reflects probably
an inclusive behavior of the plants and a good aptitude to use the dominant ions (Na+) for the osmotic
adjustment. Consequently, plants have been probably adapted to the osmotic stress by either closing theirstomata or increasing the osmotic pressure of the leaf cells
Recently, Sebnem et al. (2007) reports that the accumulation rate of Na+ in tolerant varieties is high andfound no significant difference between tolerant and sensitive plants to this level and concluded that the ratios
K/Na and Ca/Na are not useful parameters for determining the level of tolerance to salt stress in melon.
The study of genetic variability among landraces of melon on the basis of the mineral analysis hasrevealed variability between cultivars and provided for discrimination among them into three groups (Fig. 4).
The first group formed by cultivars M16, M97, M31, M131, M6, M24 and M5 characterized by a highNa+ containing, relatively low average concentrations of potassium and phosphorus; The second group
includes the cultivars M3, M95, M50, M20, M26, M125, M29, M122, JC, MAZ, that are characterized by a
low content in sodium, variable potassium level, and a low phosphorus level; The third group includes twocultivars: M15 and M61 that are characterized by moderate sodium and potassium content and highphosphorus level.
The fourth group contains M17, M16, M19, M58, LOB, M120; They have mineral leaves concentrations
that are very similar to those of the commercial variety LOB. They are characterized by moderate sodium
content while potassium and phosphorus are variable.

1,400e1,200cdd

1,000de0,800cecdc c cc0,600c0,400ccbb b bbbbbba0,2000,000
M M M M M M M M M M M M M M M M M M M M M M M M L JC M
3 5 6 9 1 1 1 1 1 2 2 2 2 3 5 5 6 9 9 1 1 1 1 1 OA
5 6 7 8 9 0 4 6 9 1 0 8 1 5 7 1Z
6 20 22 25 31 B

Fig. 3. Average content of Na+ in leaves ofdifferent melon landraces.

Fig. 4. Dendrogram of different landraces ofmelon as classified on the bases of threemineral elements.

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The last one regrouped M9 and M8 and is characterized by moderate content in sodium andpotassium and an important phosphorus level.
From this analysis, it appears that cultivars of the same groups are not primarily collected in one place.
This proves that the origin of diversity is not geographic. Some cultivars showed a similarity to thereference varieties at stake but the mineral study alone is not enough to draw complete similarities given
this must be proven to genetic scale.
4. Recommendations
If the landraces studied showed a tolerance, it is due to them being indigenous and therefore adapted
to the environmental constraints.
This study was performed to establish a hierarchical classification of studied landraces; stress
tolerance must be proved by a study with greater salt concentrations.
Variability should be studied at the genetic level because the accumulation of minerals in leaves is a
result of genotype × environment interaction.
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