II. 4. Re-evaluating the protein heterosis in hybrids of erectoides mutants in cv. Union.
H. Ahokas, Department of Genetics, University of Helsinki, P. Rautatiekatu 13, 00100 Helsinki 10, Finland. "R"
Mikaelsen (1973) reported a protein content heterosis of about 40% in the heterozygote of two allelic erectoides mutants of cv. Union, viz. H5 and H14. Since the material was discarded by accident at Mikaelsen's laboratory when he was abroad, Dr. Mikaelsen could not re-examine his finding (Mikaelsen pers. comm.). The present work is an attempt to test the possible heterosis in F1 plants in Finland, an environment different from that in Austria.
The stocks were obtained from Dr. H. Walther (GSF, Grunbach, FRG). A third mutant line H5-9 was also included in the diallelic crosses. The lemmas were not cut at emasculation, so that normal-formed F1 seeds were born in crosses. Four hundred kg/ha of an N-P-K (15-8.7-12.4) fertilizer was drilled crosswise in relation to the plant rows before planting. The seeds were hand-spaced in 1 m rows, 21 seeds per meter (at 5 cm intervals) with a row spacing of 15 cm. The material was randomized in six blocks, although the reciprocal hybrids were raised side by side. With this arrangement, the evident intergenotypic competition was probably reduced. The parental cultivar and mutant lines were also grown in double rows. Only one was selected at random for harvesting by tossing a coin. The blocks were surrounded by additional plant rows of the erectoides mutants. Automatic Kjeldahl analyses of l g meal samples were acquired from Viljavuuspalvelu Oy.
The erectoides mutants and F(l) seeds raised on them had a slightly lower emergence and seedling survival, which may have affected their yields. The results are presented in Table l, where attention is paid to only a couple of points in this text. The highest Kjeldahl N x 6.25 protein content appeared in the erectoides mutant Hl4 which is in accordance with the mean values obtained by Gaul et al. (1976) with these stocks in eleven environments. The erectoides hybrids H5-10/H14 and H14/H5-10 do not have a higher protein content than the better parent H14 itself, while the protein yield is slightly better in these hybrids than in H14.
These results do not support the striking heterosis of protein content. However, it is not entirely certain which protein determination method has been used by Mikaelsen (1973). If he used the DBC method, as is possible, the difference in methods might still explain the difference in results. This explanation, which would mean a higher basic amino acid content in the protein of the hybrid, can be checked because the meal is still available. The nitrogen level (60 kg/ha) was not necessarily limiting to the expression of heterosis, since the mutant H14 is already superior to cv. Union at the level of 40 kg N per ha (Mikaelsen 1972).
Acknowledgment:
The work was done under the auspices of the Research Council for Agriculture
and Forestry (the Academy of Finland) which also supported it.
References:
Gaul, H., H. Walther, K. H. Siebold, H. Brunner, and K. Mikaelsen. 1976.
Estimates of selection parameters in protein mutants of spring barley.
IAEA, STI/PUB/426:73-83.
Mikaelsen, K. L972. An erectoides mutant in barley with increased seed protein content. Hereditas 72:201-204.
Mikaelsen, K. 1973. Studies on the inheritance of the high seed protein content of an erectoides mutant (H-14) in barley. IAEA, STI/PUB/ 320:217.
