ROOT WATER-UPTAKE AND PLANT GROWTH IN TWO SYNTHETIC HEXAPLOID WHEAT GENOTYPES GROWN IN SALINE SOIL UNDER CONTROLLED WATER-DEFICIT STRESS

Abstract

A key breeding objective for bread wheat grown in the dry regions of Western Asia and North Africa is to enhance its adaptation to drought and its related salinity. Two newly-developed genotypes of synthetic hexaploid wheat, ‘SW-3’ and ‘SW-4’, their parental durum wheat variety ‘Jennah Khetifa’ and a dry-land bread wheat variety ‘Cham 6’, were compared for plant growth in saline hydroponic culture. They were also compared for root water-uptake and growth in soil culture in pots under combined water deficit and salinity stresses. Under saline hydroponic culture for five weeks, ‘SW-3’ developed a larger leaf area than the other genotypes. In saline soils for the period up to maturity, ‘SW-4’ and ‘Cham 6’ had higher root water uptake than the others. Only ‘SW-4’ developed normal grains and was clearly tolerant of soil salinity. ‘Cham 6’ developed normal spikes but ceased to fill the grains after heading. It may be assumed that salinity stress depressed root water-uptake at the early stages of growth, but the toxic effects of salinity stress increased in the later stages. The four wheat genotypes used in this study responded differently to salinity stress whereas water-deficit stress resulted in relatively few genotypic differences. ‘SW-4’ was more tolerant of soil salinity than its durum wheat variety parent ‘Jennah Khetifa’. This could be a useful genetic resource for improving ‘Cham 6’, which was relatively tolerant of water-deficit stress but sensitive to salinity stress after heading.