Vegetable Species in the Palm Grove of The Ouargla Region (Algeria)

. The present work on the cultivation of winter vegetable species, which was carried out in the perimeters of development of the six communes of the region of Ouargla. We found that the biodiversity recorded is 16 species and 09 botanical families, during the study period. The most frequent botanical families are : Liliaceae (Allium cepa L.), Chenopodiaceae (Spinacia oleracea.), Asteraceae (Lactuca sativa) and Apiaceae (Daucus carota .). Many local cultivars have been identified; their identification is mainly based on: the origin of the seeds, the shape and color of the fruits. According to the average richness and diversity index calculations, we found that the stations of Sidi Khouiled and Hassi Ben Abdallah have a great diversity, unlike Rouissat and Ouargla where the diversity is low. The local diversity seems to be threatened, this is due to several causes among others the non-reasoned selection of local cultivars and the introduction of hybrid seeds which allows us to validate the first hypothesis that says (the development projects have favored the introduction of many new vegetable species, not traditionally cultivated in the areas and have favored the use of hybrid varieties, with high production potential. This policy induces a genetic erosion, especially for local cultivars) and to reject the second hypothesis that says (the development perimeters participate in the preservation of local cultivars, which ensures their sustainability in the medium and long term).


I. INTRODUCTION
Algerian oases have been the cradle of know-how, creativity and continuous adaptation that have led to the creation of sites of great biological diversity. There is an exceptional diversity of date palms and associated crops such as tree species, cereals, vegetables, fodder, aromatic and medicinal. These crops are generally intended to satisfy family needs and local markets [1][2][3][4][5][6][7][8][9][10]. Agriculture in the Ouargla region has undergone, in recent decades, a very remarkable development in terms of agricultural areas, which are being extended thanks to the development of new perimeters and in terms of crop diversity in crop production systems, which tends more and more towards intensive agriculture. This calls for the use of new techniques to ensure good production, in quantity and quality. In this region, agriculture is characterized by two agricultural systems: the old system, defined by the oases and the new system, represented by the new land development perimeters; carried out under the various development programs. [7]. The wilaya of Ouargla has an agricultural area of 4,877,393 ha of which only 31162 ha, are currently exploited [3]. The various agricultural development programs, launched since independence, have doubled the number of date palms. The vegetable crops species have a great food and economic importance. The wilaya of Ouargla has 811 ha of vegetable crops, in irrigated, that of the region is about 191 ha, or about 24% [8]. Our objective is the identification of diversity among vegetable species grown in the development perimeters of the Ouargla region. The study will also analyze the importance of introduced varieties and the place of local cultivars that may exist in the region.
Two hypotheses are put forward:  The development perimeters participate in the preservation of local cultivars, which ensures their medium-and long-term sustainability.

 Choice of Study Stations
To study the biodiversity of vegetable species in the region of Ouargla, we based ourselves on the statistics of the Direction of agricultural Services [7] to choose the study sites. We were interested in stations with high and low potential for vegetable crops. Our surveys were carried out in six large market gardening stations in the region of Ouargla, namely: daïra of Ouargla (municipality of Ouargla and municipality of Rouissat), daïra of N'goussa (municipality of N'goussa) and daïra of Sidi Khouiled (municipality of Sidi Khouiled, municipality of Ain Beida and municipality of Hassi Ben Abdallah). The size of the majority of farms surveyed is medium (1ha-3ha).

 Sampling Method
Sampling consists of selecting elements in order to obtain objective information with a measurable precision on the whole. [9]. According to GOUNOT (1969), subjective sampling is the simplest and most intuitive form. The principle consists in choosing, as samples, areas that seem particularly homogeneous and representative of the plots [9]. For our study, we chose 10 farms in each station. In each of them, we carried out 03 surveys. The choice of these surveys was based on the diversity of species, the sampled surface is 100 m².

 Exploitation of the Results by Ecological Indices
To express the results of our study, we used ecological indices: Total richness (S), Shannon-Weaver diversity index and equi-repartition index.

 Percentage of Occupation of the Market Garden Species in the Region of Ouargla
In order to have an idea on the distribution of market garden species in the region of Ouargla and their importance, we were interested in the analysis of statistical data collected at the level of the Directorate of Agricultural Services of the wilaya (DSA), during 10 years (2006 -2015) [7]. The diversity of species in the 06 communes seems to be different. The most diverse are: N'goussa, Hassi Ben Abdallah and Sidi Khouiled. The commune of Ouargla has relatively low percentages of occupation compared to the other communes ( Figure 2) Lactuca sativa L. Lettuce ‫الخس‬ ‫سالطة‬ Overall, the inventories of species found in the region of Ouargla seem to be the same identified by [1], this can be explained by the similarities in the dietary habits of the Saharan populations and where vegetables have a capital importance. Culinary preparations between the two regions are more or less similar.
Most cultivated species do not have well-defined varieties or cultivars. The seeds used are often from a mixture of populations, grown locally and selected more or less empirically by the farmers. These populations are inherited from generation to generation. In any case, local names are often given to certain cultivars of species in order to express one or more characteristics of the plants such as: the origin of the seeds, the shape of the leaves, the color of the fruits. For this purpose, farmers give names to different populations based on (4) criteria: The equitability indices obtained vary from 0.18, in N'goussa station to 0.16 in Ain Beida, Hassi Ben Abdallah and Sidi Khouiled stations. No value is close to 1, which shows that the equitability is low at all stations studied. The equitability index tends towards 0 because most of the farms are based on the cultivation of one or two main species, the others are considered as secondary or even sometimes marginal species.

 Problems Encountered and Prospects
The surveys carried out in the Ouargla region revealed several problems, the most widespread at the level of farms are -The lack of financial means As perspectives, farmers do not seem to have a strategy for the preservation of biodiversity or its development. The choice of species and even varieties is dictated by market demand.
Raising farmers' awareness of the need to preserve local cultivars (in situ conservation) is essential. There are also opportunities to exchange plant material between localities in order to encourage a reasoned selection of local cultivars. It is true that the use of hybrid seeds cannot be stopped, but in the long and medium term, a strategy must be devised to manage seed introductions. The ITDAS station in Hassi Ben Abdallah is well suited to manage these introductions and assist farmers in choosing their seeds.

CONCLUSION
The agriculture of the 21st century must find a compromise between productivity and sustainability. Specific diversity is the most important: nature abhors homogeneity, and there are almost no mono-specific ecosystems on the globe, except in some extreme desert conditions. The first consequence of this species diversity is spatial heterogeneity, which translates into a great wealth of interfaces between species [6]. At the end of our work on the biodiversity of winter vegetable species, which was carried out in the development perimeters of the six communes of the Ouargla region, we found that the biodiversity recorded is 16 species and 09 botanical families, Numerous local cultivars have been identified; their identification is done mainly according to: the origin of the seeds, the shape and the color of the fruits.
The average richness and diversity indices of Shannon Weaver and equitability showed that the stations of Sidi khouiled and Hassi Ben Abdallah represent the most important diversity; those of Rouissat and Ouargla, with a diversity which seems to be weak. According to the interview established with farmers, the lack of certain species in the study area may be due to two reasons: either to a poor adaptation to the edapho-climatic conditions of the region, including temperature, salinity of water and soil, water insufficiency (case of Sidi Khouiled) on the one hand; and / or or disinterest of farmers to certain species in relation to the main crop which is the date palm and market demand.