Adaptation of barley (Hordeum vulgare L.) to harsh Mediterranean environments

Abstract

In the low-rainfall environments of the Middle East, genetic progress in grain yield through direct selection is slow. This study was conducted to identify a combination of traits or plant ideotype in barley (Hordeum vulgare L.) conducive to adaptation to terminal drought-stressed low-rainfall Mediterranean environments. Thirty-six two-rowed barley entries, ranging from local landraces and breeding lines to European cultivars, were grown at different sites in northern Syria. Observations were made on growth habit, plant colour, growth vigour, ground cover, cold tolerance, and heading date. Good ground cover and vigour in spring and early heading were related to higher yield under terminal drought. However, this good performance in spring was associated with two contrasting plant ideotypes in winter. The first ideotype, characteristic of landraces from Mediterranean environments with cold winters, was based on a moderate vernalization requirement. This assured appropriate cold tolerance, associated in winter with prostrate growth habit, dark plant colour and poor early vigour. It enabled heading early enough to avoid terminal drought stress. The second ideotype was based on avoidance of terminal drought stress through early heading and good early vigour. The associated higher vulnerability to low-temperature stress was compensated by an ability to recover from cold damage. This ideotype was characteristic of entries from Mediterranean environments with mild winters. Since environmental stresses in the Middle East are variable, individual traits can only successfully be incorporated into a breeding program if they are considered within the entire plant ideotype.