Somatic Cell Selection to Genetically Improve Plant Water-Use Efficiency and Tolerance to Stresses

Water conservation may depend on development of improved crop plant water-use efficiency and tolerances to drought and heat stresses. This project tested the hypothesis that increased production of uncommon polyamines may confer greater crop water-use efficiency and/or tolerances to drought and heat stresses, using alfalfa (Medicago sativa L.) and cotton (Gossypium hirsutum L.) as model systems. The genetic strategy involved selection for cellular tolerance to known inhibitors of three biosynthetic enzymes in the polyamine pathway, which should lead to overproduction of the targeted polyamines; and evaluation of selected and nonselected cell lines for cellular tolerance to induced water deficit (alfalfa) or heat (cotton) stresses. Cotton and alfalfa genotypes were chosen that were known to be tolerant or susceptible to heat or drought stress conditions, respectively. Under certain growth conditions, cell cultures expressed stress tolerance traits that correlated with whole plant stress tolerance. Selected cell lines of cotton were recovered that exhibited stable adaptations to the inhibitors or high temperature growth conditions. Unfortunately, all alfalfa cell lines were lost in a devastating laboratory fire. Many of the selected cell lines of cotton with adaptations to the inhibitors exhibited enhancements in the activity of one or more, in several cases all three, of the targeted enzymes. The activities of all three enzymes increased in response to cotton cell adaptation to high temperature alone, suggesting a relationship between adaptation to high temperature and uncommon polyamine biosynthesis. Attempts to regenerate plants from selected cell lines for heritability studies were not successful.