Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Etude de la variabilité des populations de mil ( Pennisetum glaucum (L.) R. Br.) cultivées dans les régions arides tunisiennes et sélection de variétés plus performantes

Auteur : Loumerem, Mohamed

Université de soutenance : Universiteit Gent

Grade : Doctor of Philosophy (PhD) 2004

Résumé
In the Tunisian arid regions where annual rainfall is less than 200 mm and soils are poor, the farmers developed a complex cropping systems known as ’culture de puits de surface ’. These are complex productions systems with multiple components combining several crop and animal production objectives. Farmers maintain a balance between a very successful of production system and high added value. In this system, pearl millet plays a very important role : the grain assures subsistance food and its straw is used for cattle feeding and the construction of huts. We used and developed methodologies defining and guiding priority actions to achieve the research objectives (prospection, evaluation, conservation and selection). This study of the genetic variability of the pearl millet landraces of Tunisian dry regions shows an important phenotypical variability for the majority of the studied characters. Time to flower varied from 30 to 66 days after sowing. Plant height ranged from 59 to 314 cm with a mean of 197.86 ±0.43. The number of tillers varied between 0 to 19 per plant. Considerable variation in spike shapes was observed. However, frequency distribution of different spike shapes shows the predominance of lanceolate (23.7%) followed by oblanceolate (23.5%), cylindrical (18.3%), conical (15.7%), candle (8.7%), spindle (6.6%), club (3.1%) and globose (0.3%) shapes. The landraces collected mostly produced large, grey-coloured, obovate seeds, with partly corneous endosperm. Analysis of variance (ANOVA) was performed to compare variation between the different landraces. The differences are highly significant at α=0.05 for all characters studied. Duncan and hierarchical clustering were carried out to estimate resemblance and to group landraces into homogeneous classes (clusters). The resulting dendrogram shows three principals clusters regrouping landraces according to their geographical origins or farming conditions. Pearl millet germplasm from Tunisia’s arid region presents a wide range of genetic variability. It can be used as a starting basis for breeding programmes to select high yielding varieties tolerating adverse arid conditions. The selection work was directed towards the creation of synthetic varieties with high yield as well as a good adaptation to the farming systems of ’puits de surfaces’ system. The synthetic varieties do not produce high yields as hybrids during the first year of cropping, but they have at least the advantage to continue to express sufficient high yield during two or three following generations. So seed renewal is only needest every 3 to 4 years. The increase in grain yield by unit of area was the main objective of our selection but a particular attention was given to straw and fodder yield in order to meet the secondary needs of certain farmers. The main results have been records first on station (IRA) and were then confirmed through field tests and participatory evaluation tests with the farmers. At the end of the third year of selection, we obtained an improved plant material whose performances meets the assigned objectives

Mots clés : Pennisetum glaucum, Pearl millet, Tunisia, Arid, Biological sciences, Plant propagation

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