Genotypic Variation for Glycinebetaine Accumulation by Cultivated and Wild Barley in Relation to Water Stress¹

Abstract

The accumulation of betaine (glyclnebetalne, N,N,N‐trimethylglycine) in barley (Hordeum vulgate L.) during water stress may be of adaptive value. The objective of this research was to evaluate the variability for betalne level among genotypes of H. vulgare and H. spontaneum C. Koch in preparation for a physiological‐genetic assessment of the adaptive value of betaine accumulation. Betaine was determined using either a pyrolysis/gas chromatographic method or a periodide spectrophotometric assay, specially modified for screening. In controlled environment tests, 339 genotypes were grown to the four‐leaf stage under well‐watered conditions and analyzed for shoot betaine level; 145 of these were also tested under water‐stressed conditions. There were significant differences for betaine level among genotypes, both without and with water stress (approximate ranges of betaine levels: 10 to 40 μmol/g dry wt in well‐watered conditions; 35 to 90 μtmol/g dry wt under stress). The betaine levels of stressed plants were significantly correlated with those of unstressed plants of the same genotype. Thirteen H. vulgare cultivars which were high and low accumulators in controlled environments were grown in the field under simulated dryland conditions and betaine was analyzed in the upper leaves. At the ear emergence stage, significant variation for betaine level was observed among cultivars although there were no significant differences in their water status. Those cultivars that accumulated either high or low levels of betaine in controlled environments accumulated respectively high or low levels in the field, the correlation among cultivars in the two environments was highly significant (r = 0.71). These results indicate that genotypic variability for betaine level is expressed in both controlled environments and in the field, and that this variability is unlikely to be due solely to variability for water status. Physiological‐genetic studies of the adaptive role of betaine may thus be possible.

Preliminary Genetic Studies of the Phenotype of Betaine Deficiency in Zea mays L.

“…There may be significant genetic variability for other nuclear encoded or cytoplasmic encoded genes that can affect betaine and/or amino acid levels severalfold within this germ plasm. Precedents for such nuclear genes influencing betaine level three-to four-fold have been set for barley (5,6,8,13), and it is not unreasonable to suppose that such genetic differences may also exist in maize. Random segregation for the 1506-specific recessive gene (and its dominant allele) and other genes which may influence betaine and/or amino acid levels an additional three-to four-fold might account for the striking 400-fold range of betaine:amino acid ratios observed in the 1146 x 1074-and 1146 x 1506-F2 populations of rather modest size (< 140 individuals total).…”

The role of cotyledon metabolism in the establishment of quinoa (Chenopodium quinoa) seedlings growing under salinity

“…Aliquots of the extract without desalting were used for proline determination according to Ting and Rouseff (1979). Glycinebetaine was extracted using the method of Ladyman et al (1983) with minor modifications. Briefly, 0.1 g FW of frozen cotyledons were homogenised in 2 ml of distilled water with a mortar and pestle, and then sulphuric acid added to make a final concentration of 0.5 M. The homogenate was shaken for 18 h at room temperature and centrifuged at 3000 × g for 10 min.…”

Solute Accumulation in Tobacco Cells Adapted to NaCl

“…After washing the column with 2 x 4 ml H20, the QACs were eluted with 2.5 N HCl (3 x 2 ml) and brought todryness under a stream of compressed air. QACs were measured according to the procedure of Ladyman et al (17) (Fig. 2, A, C, E, and G).…”