Increasing salinity of soil and water threatens agriculture in arid and semiarid regions. By itself, the traditional engineering approach to the problem is no longer adequate. Genetic science offers the possibility of developing salt-tolerant crops, which, in conjunction with environmental manipulation, could improve agricultural production in saline regions and extend agriculture to previously unsuited regions.

Four ecotypes of the species Lycopersicon cheesmanii ssp. minor (Hook.) C.H. Mull. from the Galapagos Islands were compared with L.escukntum MIlI cv. VF 36 with respect to salt tolerance. The L. cheesmanii ecotype that proved most salt-tolerant was selected for detailed comparison with the L. escukntum cultivar. Plants were grown in modifled Hoagland solution salinized with synthetic seawater salt mix. Growth rates under saline conditions were examined and amino acid, sugar, total amino nitrogen, free acidity, and Na and K levels in the tissues of the most and least tolerant plants were measured under salt stress and nonstress conditions. Results indicate that all Galapagos ecotypes were far more salt-tolerant than was the escukntum cultivar. They could survive in ful strength seawater nutrient solution while the esculentum cultivar could not in most cases withstand levels higher than 50%o seawater. Growth rates were reduced in both species under saline conditions but the esculentum cultivar was more severely affected. High levels of total amino nitrogen, specific amino acids, and free acidity along with low sodium content were found in the salt stressed VF 36 cultivar. The opposite responses were noted in the salt stressed treatments of the Galapagos ecotype. Tissue sugar levels did not appear to be similarly correlated with salt stress in either species. Potassium content fell sharply during salinization in the Galapagos ecotype while in the esculentum cultivar it declined relatively little even at high levels of salinity.Almost two decades ago, Bernstein and Hayward (1) wrote: "An understanding of the physiology of salt tolerance of plants is important for an effective approach to the salinity problem, which is of increasingly widespread occurrence." Coupling an understanding of the genetic control of salt tolerance with this physiological approach adds the further dimension of promising to lead to the development of salt-tolerant crops (4, 5). It is axiomatic in modern physiology and biochemistry that specific capabilities of organisms depend on the synthesis of appropriate enzymes, this synthesis in turn being gene-controlled. As sensitive plants in respect to a number of pertinent physiological and biochemical parameters (2, 5, 9, 13). It is becoming evident that the combined tools of the plant physiologist, geneticist, and breeder must be brought to bear on the increasing salinity problems confronting irrigation agriculture on a worldwide scale. Furthermore, if strains of crops capable of coping with seawater or brackish water salinity could be generated, what is now a problem could become a vast opportunity for crop production by tapping the immense wealth of water and mineral plant nutrients of the oceans without the energy-costly process of industrial desalination.The experiments reported here represent a contribution to this approach. Two species of the tomato, one salt-tolerant, the other salt-sensitive, were compared under saline and nonsaline conditions in regard to a number of physiologica...

The roles of K+ and Na+ in plant nutrition have sparked numerous investigations which ultimately have led to the conclusion that K+ is the only monovalent cation that is essential for all higher plants (7) but that Na+ can have beneficial effects on plant growth. Sodium has been shown to be essential for a few species (4) and for improvement in growth and productivity in several crops, particularly those in the family Chenopodeaceae (11,15,23). There is substantial evidence that plants of moderate to high salt tolerance may, under saline conditions, accumulate large amounts of salt and that Na+, in particular, can make a significant contribution to both the osmotic relations (5,8,13,21)

No abstract

Crosses were made between a salt tolerant wild tomato [Lycopersicon cheesmanii ssp. minor (Hook) C. H. Mull.] and a domestic cultivar (L. esculentum Mill. cv. Walter). Selections were made from resulting progenies for salinity tolerance at germination, seedling establishment, and the reproductive stage of their life cycle. The selected progenies were tested for survival and fruit production in salinized solution culture experiments, and in field greenhouse trials where they were irrigated with various dilutions of seawater applied to sand. Salt tolerance was shown to be a heritable trait. Plants selected from the F2 and successive backcrosses to ‘Walter’ survived and produced fruit when irrigated with up to 70% seawater in the sandy soil culture trials, whereas ‘Walter’ did not survive.