Development and characterization of near‐isogenic lines of sorghum segregating for glycinebetaine accumulation

Abstract

Glycinebetaine (GB) is a compatible solute synthesized by species in a number of plant families, including some grasses such as sorghum (Sorghum bicolor L. Moench). A recombinant‐inbred (RI) population was developed from a cross between GB‐deficient (IS2319) and GB‐accumulating (P932296) sorghum genotypes. The proportions of GB‐accumulating lines in both the F5 and F7:8 generations of this RI population were higher than expected, possibly due to some beneficial effect of GB accumulation on plant growth, survival or seed set. GB levels varied widely in lines of the RI population that were grown under controlled conditions, suggesting genetic control not only for the presence or absence of GB, but also for the level of GB. This hypothesis was tested by analysing individual plants from lines identified as accumulating low, medium or high concentrations of GB based on the F5 and F7:8 screens. The level of GB was conserved within lines, supporting the hypothesis of genetic control of relative GB levels within accumulating lines. Two pairs of near‐isogenic lines (NILs) with contrasting GB levels within pairs were developed from the RI population. The stable inheritance of the GB phenotype and isogenicity of these NILs were confirmed with progeny tests and molecular marker analysis, respectively. Labelling studies demonstrated that the deficiency in GB accumulation was at the choline oxidation step.