GrainGenes

11. 29. Ripening and yield in barley with high-lysine gene lys-3a.

I. Kreft, B. Javornik and L. Kajfez-Bogataj, Biotechnical Faculty, University E. Kardelj, YU-61 001 Ljubljana, Yugoslavia."R"

Barley with high-lysine gene lys-3a (Jensen and Doll, 1979) of Risø mutant 1508 (Ingversen et al., 1973), like other studied high-lysine lines, has a lower yield than normal lysine high-yielding cultivars. This is apparently connected with decreased seed weight, reduced content of total carbohydrates and increased content of free sugars in high-lysine lines (Kreis, 1978; Oram and Doll, 1981). Endosperm homozygous for lys-3a is typically shrivelled, with a strong dorsal indentation. This morphologic characteristic is not seen in fully formed, wet ripening kernels. It is, however, visible when the seeds are dry. The detailed mechanism of the effects of the lys-3a gene is not yet known.

F2 seeds from the cross of barley KVL 468 (Toft Viuf, 1970) and Risø mutant 1508 were received from D. von Wettstein and L. Munck, Carlsberg Research Center, Copenhagen, Denmark. In F8, several interesting spring barley lines were selected, among them a high-lysine line 22 (with the lys-3a gene) and a high-protein line 26 (without the lys-3a gene). The field experiment was sown in Ljubljana on March 22, 1982.

The content of dry matter of the flag leaf, of the uppermost 20 cm of the stem, of the kernels and of the rest of the main spike was determined during ripening (July 2, 6 and 9; 1982) in line 22, line 26 and cultivar Union. On July 2, the fresh weight of seeds was measured as an estimation of the volume of the seeds. The results are shown in Tables 1 and 2. Figures are means of 5 plants.

Table 1. Mean mass of kernels of main spike in three barley genotypes (in mg).
 

Table 2. Mean mass of uppermost 20 em of main stem in three barley genotypes (in mg).

On July 2, the lines did not differ significantly from cv. Union either in estimated volume of kernels or in content of dry matter. Later dry matter content of kernels of cv. Union and line 26 rose significantly (P=0.01), but the dry matter content of line 22 remained unaltered. The dry matter content of the uppermost 20 cm of the main stem was, in the meantime, reduced significantly in all three barley varieties without any significant difference among them. There were no detectable differences in the dry matter content of the other studied parts of the barley plants. The results indicate that there was an equal movement of photosynthates into kernels in all three barley varieties up to about July 2, but that after that date it was blocked in the high-lysine line 22. As the dry matter content of the stems in all three barley varieties was equally reduced, the lack of available photosynthates in the plant was probably not a reason for the blocked transport of photosynthates into the kernels in line 22. The estimated volume of kernels on July 2 indicates, that the morphology of the sink (for example the number and volume of cells in the endosperm) was also not a probable reason for the reduced flow of photosynthates.

The electrophoretic patterns of the water soluble fraction of proteins, which also contain several enzymes, are different in Risø mutant 1508 to those of the parent cv. Bomi (Kreft, 1976). Allison (1978) found altered amylase activity in Risø mutant 1508 in compaRisøn to Bomi. According to Lingle and Chevalier (1984) the inability of endosperm to convert sucrose to starch may create a physiological barrier to sucrose movement into the endosperm.

It is possible, that the lys-3a gene, at some stage of ripening, blocks the conversion of sugar to starch, and that the high concentration of sugars in the endosperm prevents the unloading of assimilates from the transport mechanism. Thus transportable assimilates, present in or moving through the peduncle, are in lys-3a barley moved to some other parts of the plant.

References:

Allison, M.J. 1978. Amylase activity and endosperm hardness of high lysine barleys. J. Inst. Brew. 84:231-232.

Ingversen, J., B. Koie and H. Doll. 1973• Induced seed protein mutant in barley. Experientia 29:1151.

Jensen, J. and H. Doll. 1979. Gene symbols for barley high-lysine mutants. BGN 9:33-36.

Kreft, I. 1976. Electrophoretic protein patterns in some barley mutants. Genetika (Beograd) 8:159-161.

Kreis, M. 1978. Starch and free sugars during kernel development of Bomi barley and its high-lysine mutant 1508. In Seed Protein Improvement by Nuclear Techniques, IAEA, Vienna:115-120.

Lingle, S.E, and P. Chevalier. 1984. Movemant and metabolism of sucrose in developing barley kernels. Crop Science 24:315319•

Oram, R.N. and H. Doll. 1981. Yield improvement in high lysine barley. Aust. J. Agric. Res. 32:425-434.

Toft Viuf, B. 1970. Undersogelser vederorende sortvariation i hvaelstofindhold og proteinkvalitet hos byg, Licentiatafhandling, KVL:2-78.

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