A comparison of procedures for evaluating and selecting alfalfa landrace germplasm for tolerance to salinity

Abstract

In arid and semiarid regions, salinity may affect alfalfa (Medicago sativa) productivity and survival due to either cultivation on salt-affected soils or the use of salinized irrigation water. Exploiting germplasm evolved under salt-stress conditions offers opportunities for crop tolerance improvement. In the first phase of the current study, four reportedly salt-tolerant landraces originated from stress-prone areas of West Asia or North Africa and two reference commercial cultivars underwent three evaluation trials according to different methods, namely, seed germination in saline water, in vitro testing of young plants, and greenhouse evaluation of adult plants in Cone-tainers. Experimental populations obtained by intercrossing landrace genotypes selected according to each evaluation method were subsequently evaluated under stressful field conditions in two regions featuring different salt stress type, namely, southern Tunisia (irrigation with saline water) and northwestern Argentina (rainfed cropping in saline soil). Landrace ranking for salt tolerance differed somewhat depending on the evaluation method, and the proportion of selected plants per landrace depended accordingly on the method. In each field experiment, there were two evaluation phases, and the second phase corresponded in both cases to harsher conditions. The in vitro evaluation and selection resulted in potentially more useful selected germplasm than the other evaluation methods. The field experiments highlighted the large specific adaptation effects that affected the response of salt-tolerant germplasm across the two regions.