沙漠研究 19-1, 205- 208 (2009 )Journal of Arid Land Studies“Desert Technology IX ”
Refereed Paper

Characterization of Several Local Cultivars of Watermelon Collectedfrom Arid Region in Tunisia
Mokhtar ELBEKKAY1, Layla LAARAYEDH1, Rim LAMARI1, Hamadi HAMZA1, Ali FERCHICHI1
Abstract: This study reports on the analysis of 8 local watermelon cultivars (Citrullus lanatus(Thumb)) collected in the South of Tunisia which were compared to two introduced
watermelon cultivars widely-grown in this arid area. The analysis was based on thecharacterization of fruits. The Principal Component Analyze (PCA) showed that the threemodern cultivars constitute a distingue group specified by their lower weight fruit and theirrelatively high fructose and glucose contents. However, it was found that the eight local
cultivars was more variable and its belong to two diverse groups. This study clearly shows theneed to safeguard and manage this precious local germplasm both ex situ and in situ, as thismaterial may contain valuable genes for future breeding activities and also future cultivation
practices.
Keywords: Arid lands, Biodiversity, Quality, Watermelon

1. Introduction
Watermelon (Citrullus lanatus (Thumb)) is originated in Africa and has a long history of cultivationin Africa and the Middle East. It has been an important vegetable in Egypt for at last 4000 years(Robinson and Deker-Walters, 1997). Watermelon is one of cultivated crops in the world. The
production in 2007 exceeded 93 millions tonsA).
In Tunisia, watermelon is largely consumed in summer as a fresh fruit. This cucurbit is cultivated invarious areas in the country and occupies more than 16000 ha representing approximately 10% of the total
cultivated area with vegetable crops (Boughalleb and ElMahjoub, 2006). Especially modern watermelon
varieties are widely used which was replaced many autochthones cultivars more and more missed
nowadays. According to Elgazzah and Chalbi (1995) and Elbekkay et al. (2008), local seeds of many
crops like watermelon, melon and tomato are nowadays hard to find in Tunisia.
The objective of this study was to examine fruit characterization diversity of several local cultivars ofwatermelon collected from arid region in Tunisia.
2. Materials and Methods
Eight cultivars of watermelon (Citrullus lanatus (Thumb)) were collected from the south of Tunisia in2005 and maintained in the genebank of the Institute of Arid Regions, Tunisia. These cultivars werecompared with two modern cultivars (cv Sugar Baby and cv Giza) which are widely cultivated in south ofTunisia. Local cultivars are coded by the letter "P" and a number of the sample (e.g. P2).
The experiment was conducted under greenhouse, heated and irrigated by geothermal water, at theexperimental station of the Institute of Arid Areas in Kebili in South Tunisia. The experiment wasconducted from December 2007 to the end of May 2008. Nine plants from each cultivar were sown under
the greenhouse on a gross sand soil. The seeds were sown with 1m × 0.5m between and within row
distances. The fertigation solution was prepared by the use of commercial water-soluble fertiliser
containing macro- and micro-nutrients (20-20-20 NPK) as noticed by Sivritepe et al. (2005).
The experimental layout of the experiment was a completely randomized block design with threeblocks. Three plants per accession were randomized within each block.
The cultivars were categorized for 20 variables of fruit characteristics according to UPOV
(International Union for the Protection of New Varieties of Plants) descriptors for watermelon (2004): timeof maturity (P) (Number of days from sowing to first mature fruit for the nine plants), average fruit weight(W), fruit Shape (Shape), type of stripes (Tstripe), width of stripes (Wstripe), size of insertion of peduncle(Size_P), depression at base (Dep_base), fruit length (Fruit_L), fruit width (Fruit_W), thickness of pericarp(T_perica), main color of flesh (C_flesh), total soluble solids content in the juice (˚Brix), Acidity
1

Laboratory of dry land farming and oasis cropping, Arid Region Institute 4119 Medenine, Tunisia;

206(determined by potentiometric titration with 0.1N NaOH to pH 8.1, using 50ml of juice and expressed aspercentage citric acid in juice), pH of the juice, electric conductivity (EC) of the juice, fructose, glucoseand vitamin C (vc) (mg/100g of flesh) contents (obtained using the chromatographic analysis using aKHAUER DEGASSER pumpK-501 HPLC (high performance liquid chromatography)), total phenol
content (measured by spectrophotometer) and the dry mature ratio (dry_m) of the chair fruit.
These variables were observed at least on three fruits for each cultivars (Table1). The data wereanalyzed using SPSS version 11.5 for a Principal Component Analysis (PCA).
3. Results and Discussion
The quantitative trait values (means ± Standard Deviation) of the nine plants per accession of the 10
watermelon accessions are shown in Table 1.
The results of PCA conducted with 20 characters for watermelon accessions were presented in Figure
1. The first three PCs (Principal Components) explained 74.74% of the variation. The first principal
component, which explains 37.26% of the variability, is determined by precocity (-0,53), weight fruit (-0,9),
shape (+0,828), depression at base (+0,747), size of insertion of peduncle (+0,904), fruit length (+0,91),
fruit weight (+0,745), acidity (-0,801), fructose content (-0,673), EC (+0,677) and VC (+0,516). The
second PC explains 22,05% of the variability and is determined by pH (-0,81), Dry mature (+0,864),
phenol content (+0,748), glucose (+0,556), thickness of pericarp (+0,662), type of stripes (-0,669). Wideof stripe (-0,752), color of chair (+0,661) and Brix (+0,689) were relatively more important than othervariables in constructing PC3 which explains 15,4% of the variability.
On the basis of the PCA, three groups can be distinguished: the modern cultivar present a distinctgroup (G1), the second group (G2) is consists of five local cultivars (P27, P28, P31, P33 and P35) and thethird group (G3) is consists of three local cultivars (P2, P15 and P21) (Fig. 1). The local cultivars (G2and G3) are earlier than the two modern cultivars (G1) considered in this study. This is especially true for
P15 with more than 15 days of precocity. Furthermore, the local cultivars showed significantly higher
Table 1. Mean values of the various watermelon quantitative traits examined.
Cultivars
Precocity(days)

Repetition

Weight(g/fruit)

9 fruits

9 plants

Size of insertionof peduncle(mm)9 fruits

Width of stripes

9 fruits

Thickness ofpericarp (mm)Fruit length(mm)Fruit width(mm)9 fruits°Brix (%)

9 fruitspH

9 fruits

EC (mS/cm)

9 fruits

Vitamin C

3 fruits

Fructose

3 fruits

Glucose

3 fruits

9 fruits

9 fruits

Phenol

3 fruits

Acidity (%)

3 fruits

Dry Mature (%)

9 fruits

P2
138,5±3,9P15
121,43±6,5P21
122,86±0,38P27
143,5±4,8P28
131,5±2,12P31
131,5±2,12P33
127,75±4,57

P35
144,5±6,26SB
136±5,46GIZA
147,5±2,02

4050±91,923587,4±188

2714,4±934

1688,9±724,11322,3±138,8

1864,8±616,11413,7±548,31766,4±219,1

912,6±448,1

881,3±514,7

10
±1,41

10,1±1,95

8,3±1,89,5±3,55±1,23,5±0,7

8±1,4

5±1,6

5±0,9

4
±1,3

11,5±0,71
10±0,73
355
±1,71
235
±2,12
8±0,71
5,82
±0,06
3,57
±0,81
4,76
±0,12
3,65
±0,78

14,86
±2,05
11,5±2,64
325,7±4,79
245,7
±2,23
8,77
±0,78
5,81
±0,12
3,51±0,40
4,59
±0,33
0,45
±0,11

9,29±1,119±1,91
270±4,16
244,3±3,91
7,14
±1,49
5,63±0,193±0,26
4,65±0,76
3,42±0,41

22,5±3,36
10,5±1,95
194±6,22128±1,13
5,75±0,35
5,73±0,08
3,74±0,27
3,35±0,17
2,99±0,97
2,16±0,11
1,05
±0,11
0,08
±0,02
8,41±0,92

13,5±0,71
7±0,32
152
±1,13
121
±0,28
6,75±0,35
6
±0,30
2,79
±0,28
1,48±0,21
4,13±0,63

6
±0, 4
6
±0,51
1625
±2,47
157,5±0,35
7±0,326,22±0,27
3,87
±0,06
2,31±0,09
3,29±0,58

9,25±2,50
9,25±2,63
220±5,83
178,8±5,118,35±0,72
6,03±0,02
3,6±0,23
4,41±0,15
3,24±0,22
2,01±0,43
0,81
±0,09
0,09±0,02
7,17±0,82

9±0,71
9±0,82190±2,83160±2,83
9±0,41
5,77
±0,02
2,73
±0,02
4,26±0,47
3,51±0,48
2,82
±0,14
1,05
±0,13
0,19±0,06
9,43
±1,42

4,5±0,54
4,5±0,64
190
±1,41
180
±2,83
7,25±0,35
5,71
±0,08
2,54±0,29
1,76
±0,62
4,36
±0,72

11,5±2,83
11,5±0,71
132±3,96
117,5±3,75
6,5±0,69
5,8±0,012,43±0,164,13±0,89
4,27±0,31
3,52±0,27
1,07±0,210,19±0,05
9,42±1,75

0000,69±0,190,06±0,01
8,45±1,120,92±0,220,09±0,02
9,42±2, 32

1,1±0,170,12±0,04
11,15±1,24000,87±0,16
0,08±0,01
5,2±0,56

0,83±0,12
0,16±0,03
6,04
±1,02

0
0,9±0,10,16±0,03
8,71±1,06

207
2,02,5G1G2

1,5GIZA

2,0P351,5P21P27

1,01,0P150,0P2SB-,5P21SBP35,5PC3PC2,5P310,0P15P33

P2GIZA-,5P33

P28-1,0-1,0G3P28-1,5-1,5P31-2,0P27-2,5-2,0-2,0-1,5-1,0-,50,0PC1,51,01,52,0-2,5-2,0-1,5-1,0-,50,0,51,01,52,0PC1Fig. 1. The results of PCA for Tunisian arid region watermelon accessions.

weight of fruit compared to Giza and Sugar Baby (SB) cultivars. However the modern cultivars havesignificantly higher fructose and glucose content than the local ones.
This study shown that the local germplasm harbours an important variation in agronomically traits.
According to Elbekkay et al. (2008), the local germplasm can be seen as a rich source of variation,although they are less adapted to the market. Therefore modern watermelon cultivars have a high appeal
by local farmers (Navikof, 1951; Loumerem et al., 2004). As in many arid land, also in Tunisian arid
region, the process of replacement by modern cultivars goes (luckily) slowly and consequently there will
be a period that both modern and local cultivars are cultivated adjacent to each other which gives a chance
to collect and preserve the local material (Louette, 2000; Maredia et al., 2000; Bardsley and Thomas,2006).
In subsequent studies we will focus on the further collection and evaluation of this local Tunisianwatermelon material including physiological and molecular studies.
4. Conclusions
Since thousands of years, farmers are relying on their own harvests to select seeds for the following
season. Nowadays, however, many farmers have become dependent on seeds supplied by seed companies
and this can eventually lead to a loss of local crop diversity. The present research focussed on theevaluation of diversity in watermelon in the arid region of Tunisia by comparing traditional local varieties
and two modern widely grown cultivars. Even though Tunisia is not the centers of origin for watermelon
our study showed that high diversity exists for traits in germplasm collected. Selection and evaluation ofgermplasm among these collections have priority for future breeding programs.
AnnotationA) FAO (2008): FAOSTAT. The FAO statistical database on-line. (http://faostat.fao.org/DesktopDefault.
aspx?PageID=567&lang=fr)
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