Screening open-pollinated maize populations for drought tolerance at germination

Abstract

Drought is one of the most limiting stresses for maize worldwide and is becoming more important in Europe as desertification reaches higher latitudes. In order to face this challenge, we need to search sources of drought tolerance primarily within the collections of adapted germplasm. In order to do so, we have screened 50 open‐pollinated maize populations from the germplasm collection conserved in the Misión Biológica de Galicia (Spanish National Research Council). We followed a simple and sensitive protocol using solutions of polyethylene glycol 6000 (PEG 6000) to simulate the effects of water stress under controlled and uniform conditions (Álvarez‐Iglesias et al., 2013). Up to five replications of each population were evaluated in Petri dishes, and four levels of drought stress were established. The 50 populations belonged to seven germplasm groups, namely Northern and Southern Spain, Canary Islands, USA, popcorn from Spain and from USA, and checks. Germination under stress was highest for popcorn, followed by the American populations, while the Spanish populations had the worst germination. Coleoptile and root growth under stress were highest for American maize and lowest for popcorn but the ranks were not consistent across stress levels and the performance of the other groups was not identical when compared for coleoptile or root growth. Therefore, none of the germplasm groups had an outstanding and consistent drought tolerance at germination and seedling development together, although the American populations showed the best compromise between germination and seedling growth under drought stress. The populations with higher drought tolerance at germination were Longfellow and AS‐A, followed by Rustler, BS17, and AS‐3(HT)C3, while the three checks, namely the commercial hybrid Anjou387 and the two synthetics EPS5 and EPS9, had the highest drought tolerance for coleoptile and root growth. We need to search more complete sources of drought tolerance in other germplasm pools.