Response of Lettuce Germplasm to Salt Stress at Different Developmental Stages
Salinity is one of the most detrimental abiotic stresses leading to considerable yield and economic losses worldwide. Lettuce is a relatively salt sensitive species, thus placing the interest in the release of salt-tolerant cultivars to enhance production in saline soils. This study aimed at investigating the response of lettuce germplasm to salt stress at the germination and at the whole plant level and to examine possibilities of early selection for salt tolerant genotypes. Fifteen lettuce commercial varieties were initially screened for salt tolerance on the basis of seed germination and seedling growth potential under salt stress conditions (0, 50, 100, 150 mM NaCl). The in vitro evaluation revealed the existence of considerable genetic variation related to salt tolerance at germination and allowed for the classification of genotypes into tolerant, moderately tolerant and sensitive to salt stress. Based on this classification, six cultivars were assessed at the whole plant level using plant height, chlorophyll content and fresh and dry biomass weight as evaluation criteria. Overall findings point to the existence of a satisfactory association of genotype performance between germination and later growth stages, thus suggesting the feasibility of screening for salt tolerance at early growth stages. This approach may considerably upgrade the efficiency of selecting suitable germplasm material for cultivation in saline soils or introgression into relevant breeding programs.