Selection of annual ryegrass for adaptation to semi-arid conditions

A collection of annual ryegrass (Lolium rigidum Gaudin) from Sardinia was evaluated for the main agronomic and physiological traits in a dense sward. Five other annual ryegrasses, among selected and commercial materials, were grown as comparator. The infra-red canopy temperature was used as an indirect evaluation method of the dehydration avoidance, and selection index for adaptation to water stress during the reproductive phase. The quantitative characters were analyzed using principal component analysis and K-means clustering. The results suggested an annual ryegrass drought-resistant ideotype: tall size, wide flag leaves and spikes with a high number of spikelets. A commercial material, imported from the USA and used as a control, showed clearly different morphological and temperature traits, probably due to an improper certification as L. rigidum of seeds distributed in Italy. Two local progenies (P15 and 32) and two natural populations ('Chiaramonti' and 'Nurra') showed clear drought-resistance traits: dehydration avoidance, wide flag leaf, high seed production capability even with late flowering. It was concluded that the infrared thermometer can help in the understanding of ryegrass responses to water stress in field conditions. This methodological approach could be suggested for screening programmes aimed at introducing new forage cultivars for the semi-arid environments to the seed market. (C) 1998 Elsevier Science B.V. All rights reserved.