Breeding for heat and drought tolerance in bread wheat by means of field and laboratory screening procedures

Abstract

About 200 varieties have been cultivated during the period 1985-1989 in quite different environmental conditions: in Italy near Milano in the Po Valley, in Sicily (Catania) and in two locations in Morocco. Optimal growing conditions, with supplementary irrigation when necessary, and both heat and drought stressing conditions have been created by either delaying the sowing date or drying up the green apparatus with chemical desiccants. Drought susceptibility indices (DSI) were therefore calculated. All the cultivars have been screened with the following laboratory tests: Cellular membrane stability in heat stress and drought stress conditions (CMShs and CMSds respectively), germination in osmotic solution (GOS), seedlings heat shock (SHS) and excised leaf water loss (LW). The relationships among the different evaluation indices for tolerance to stress conditions, their reliability and repeatability are discussed in relation to the possibility of application in plant breeding. It has been concluded that the available laboratory tests are of limited value in screening cultivars because of the high genotype x environment interactions and of the weak association with the performance under field stress conditions. On the contrary consistent associations have been found among yield related traits of varieties cultivated in very distant sites. The perspectives to cultivate the varieties bred in Southern Europe in the cereal growing areas of the Asiatic and African countries bordering the Mediterranean basin are discussed. © 1990 Taylor and Francis Group, LLC.