La secheresse est un stress abiotique qui affecte le rendement des cereales et sa stabilite dans le bassin mediterraneen. Du point de vue agronomique, l'adaptation a la secheresse est la capacite d'une plante a maintenir un rendement a travers des environnements ou les periodes de secheresse, leurs durees et leurs intensites sont fluc¬ tuantes. Le rendement etant difficile a ameliorer directement (faible heritabilite, fortes interactions genotype x environnement...), l'etude

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Etude de la tolérance à la sécheresse chez les céréales : l'orge comme modèle biologique, approche QTL

Les emblavures reservees au ble tendre (BT) en Tunisie sont rela¬ tivement inferieures a celles consacrees aux autres cereales, dont essentiellement le ble dur (BD) et l'orge. En effet, sur 1,6 million d'ha (moyenne du 8e plan) reserves a la cultures des cereales, le ble dur occupe 0,88 Mha (55 %) contre 0,55 (34 %), 0,15 (9,5 %) et 0,1 (0,6 %) respectivement pour l'orge, le ble tendre et le triticale (minis¬ tere de l'Agriculture, 1998). La superficie emblavee en BT n'a par ailleurs evolue que tres peu depuis plus de 50 annees. En contrepar¬ tie, un deficit chronique, relativement eleve, est enregistre pour cette cereale et, en moyenne, 72 % de nos besoins sont annuellement importes (O.C., 1998).

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Stabilité de la production en grains d'une collection de blé tendre : comparaison de résultats

Molecular genetic markers and other enabling technologies are now sufficiently developed for exploitation in breeding programmes. They allow the possibility of accelerating, and improving the efficiency, of breeding for abiotic and biotic stress tolerances. Barley is a good model species in which to demonstrate this. Barley is a diploid species in which genetic analysis is relatively easy, its short life cycle and inbred nature has also provided for good physiological research. The results of genetic and physiology studies can now be exploited more efficiently in breeding using the tools of contemporary biotechnologies. A programme of work has been initiated aimed at developing more stable yields in barley (Hordeum vulgare) for droughted, low input agricultural conditions of Mediterranean rim countries. Various molecular breeding approaches are to be compared which vary in gene donors, recipients and methods. Two of the approaches exploit wild barley (H. spontaneum) as a source of genetic variation for abiotic stress tolerance, the third uses an adapted landrace. Results from controlled environment experimentation will be compared with field performance in naturally stressed environments of N. Africa. The work will provide a testing ground for the application of ideas and technologies developed from research.

D. This

Papers

Molecular Breeding of Barley for Droughted Low Input Agricultural Conditions