II.29. The inheritance of high lysine and crude protein content in crosses between Hiproly and a normal lysine, low protein barley.
Odd-Arne Olsen and Knut Aastveit, Insitute of Genetics and Plant Breeding, Agricultural University of Norway, 1432 As-NLH.
Since the discovery of Hiproly (Hagberg and Karlsson, 1969), several investigations have been published concerning the inheritance of the 'hily' character. It now seems generally accepted that the high lysine content is due to a single recessive gene, lys (Munck et al., 1970). However, only in a few of the crosses where Hiproly has been involved, a segregation ratio of 1:3 has been demonstrated in the F2-generation. Munck (1972) explained these significant deviations by assuming modifiers. Linkage between the locus for high vs. low lysine (lys), and the locus for short vs. long haired rachilla (Ss) was reported by Karlsson (1972). In our studies crosses were conducted between Hiproly (ss) and the two-rowed mutant line Jcgamma 124, which is low in lysine as well as crude protein content, and in addition of the genotype SS (Olsen, 1973). In order to minimize the influence of environmental variation, the studies were based on F3-families grown in duplicate blocks and randomly selected from 341 F2-plants. As a measure of the lysine content the DBC-value per 0.500 g barley meal, divided by the KP-value was used. This measure is referred to as DBCP.
The segregation ratio for rachilla hairs differed significantly from the expected 1:2:1 ratio, with a deficiency of recessive homozygotes. Therefore, since the locus for lys and the locus for s are reported to be located in the same chromosome, it is also likely that there would be a deficiency in the number of lyslyslys endosperms in the same experiment. Due to this, and the great environmental influence upon lysine content, all DBCP values were corrected to the same KP value by means of the average coefficient of regression for Hiproly and Jcgamma 124. The distribution of this measure of lysine content, referred to as DBCPc, was then plotted for each of the classes of rachilla hairs, constant long haired, segregating and constant short haired (Figure 1). The average DBcPc-value for the three classes are well in accordance with the expectation based on a 1:2:1 distribution, assuming linkage between the locus for s and the locus for lys. This seems to verify the conclusion that high lysine content is inherited as a single recessive gene.
The distribution of F3-fanilies with regard to crude protein content (KP) was found to be distributed near to the normal distribution, indicating typical quantitative character inheritance, and showing positive as well as negative transgressions (Figure 2). As the F3-families were also scored for heading date, grain yield per plant and 100 grain weight, the coefficient of correlation between all possible pairs of characters were computed. For example, the coefficient of correlation between KP and grain yield per plant was -0.48, and between DBCPc and grain yield per plant -0.45. Several interesting recombinants were obtained, which will be selected for further studies. The studies will be extended to other high lysine barleys.
References:
Hagberg, A. and L. E. Karlsson. 1969. Breeding for high protein content and quality in barley. New approaches to breeding for improved plant protein, LkEA/FAO, STI/PUB Vienna 212:23-28.
Karlsson, K. E. 1972. Linkage studies on a gene for high lysine content in Hiproly barley. BGN 2:34-36.
Munck, L. 1972. High lysine in barley - a summary of the present development in Sweden. BGN 2:54-59.
Munck, L., K. E. Karlsson, A. Hagberg and B. O. Eggum. 1970. Gene for improved nutritional value in barley seed protein. Science 168:985-987.
Olsen, O. A. 1973. Genetical and ultrastructural studies of Hiproly barley. Thesis, University of Oslo.
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