Germination and emergence variability of alfalfa (Medicago sativa L.) landraces collected in Southern Tunisia oases

Variability in germination under controlled conditions with and without salt, seeds characteristics and field emergence were evaluated for 20 landraces of Medicago sativa ssp sativa, a forage legume collected from three sites in Tunisia. Highly significant differences were recorded among the landraces (p < 0.001) for all the characters studied except tegument colour. Number of seeds produced per plant ranged between 378 and 460 seeds g(-1). Emergence responses of seeds were different among landraces and sites and their values ranged between 12 to 45%. Salt stress (150 mM) caused substantial reduction in final and rate of germination of all the landraces with an average decline of 62.4 and 69.7%, respectively. Final germination values ranged from 26.5 to 75.75% when supplied distilled water. However, final germination values ranged from 10.75 to 32.5% when the seeds were exposed to saline water (150 mM). Rate of germination ranged from 12.75 to 63.25% and from 6.25 to 21.25% at non-saline and salt stress, respectively. Cluster analysis separated the 20 landraces into four clusters. Three landraces in the first cluster had the lowest germination and the greatest field emergence. One landrace composed the second cluster and showed both high germination and field emergence. Two landraces in the third cluster presented greater germination and low emergence. The other landraces constituted the fourth cluster and had intermediates emergence and germination.