Evaluation of Lettuce Genotypes for Salinity Tolerance

Lettuce is one of the most commonly used salad vegetables and considered to be a relatively salt sensitive crop. Salinity is a major constraint to crop production in all important lettuce districts of the U.S., and the water quality problem is exacerbated by the climate change. In order to identify salt-tolerant lettuce genotypes, 174 cultivars and germplasm accessions (54, 39, 34, 32 and 15 genotypes of butterhead, crisphead, romaine, leaf, and wild types, respectively) were screened in sand cultures under greenhouse conditions. Leaf fresh and dry weight (FW and DW), chlorophyll index and maximal photochemical efficiency (Fv/Fm) were measured four weeks after the varieties were seeded and grown in Hoagland nutrition solution either with or without 30/15 mM NaCl/CaCl₂. Generally chlorophyll index increased while Fv/Fm remained unchanged under salt stress. Some lettuce varieties showed salt tolerance (less than 10% reduction in FW) such as Morgana, PI 358020c, PI 342515 (butterhead), Laura (crisphead), PI 289023, PI 278066 (romaine), PI 171676a, PI 177423, PI 358018b, PI 342477 (leaf). The result of this study indicated that lettuce genotypes differ greatly in their salt sensitivity, which could be useful for growers to choose cultivars and for breeders to improve lettuce adaptation to salinity stress.