II. 12. Genetic studies with proanthocyanidin-free barley.
Duane E. Falk. Joint Doubled Haploid Barley Breeding Programme, C/-CRD-DSIR, Private Bag, Christchurch, N.Z. "R"
The discovery of proanthocyanidin-free mutants in barley (Jende-Strid, 1976) has created the possibility of brewing beer with increased chill-haze stability (von Wettstein, et al., 1980). Histological examination of barley seeds has identified the aleurone and testa (Jende-Strid, 1978) or the testa alone (Aastrup, et al., 1984) as the tissue which contained proanthocyanidin. In such cytological studies it is difficult to accurately separate the aleurone and testa tissues. Since the aleurone and testa are of different genetic origin, it may be possible to determine which of these tissues contain the proanthocyanidin by creating genotypes in which the aleurone and testa contain different alleles for proanthocyanidin presence or absence.
Localization of proanthocyanidin in barley seed
Reciprocal crosses were made between proanthocyanidin-free barley genotypes
possessing the ant13-13 or ant17-148 alleles (materials kindly
supplied by Carlsberg Plant Breeding) and normal barley genotypes with
(Triumph) and without (Mata) anthocyanin in the plant tissues. Half seeds
of the parents, crosses and selfed F1 plants (F2 seeds) were stained with
1% vanillin in 6M HC1 (as per Aastrup, et al., 1984) to determine whether
proanthocyanidins were present or absent. Five seeds of each parent, 10
seeds of each cross combination and 25 seeds of each selfed F1 plant (F2
seeds) were tested.
The genetic constitution of the testa, aleurone and embryo were determined based on the testa being diploid and derived entirely from maternal tissue, the aleurone being triploid with one sperm of the male combining with the two polar bodies of the female and the embryo being diploid by receiving one genome from each parent.
The results of the reciprocal crosses (Table 1) indicate that the genotype of the testa corresponds to the vanillin reaction of the crossed seed. The seeds from the selfed F1 plants confirm this as the testas would all be identical and heterozygous while the aleurone should be segregating for different combinations of the Ant and ant alleles. Thus it would appear that the testa tissue alone contains the proanthocyanidin compounds in the barley seed. This genetic evidence confirms the histochemical study of Aastrup, et al., (1984).
Table 1. Vanillin tests on barley seeds with different testa and aleurone genotypes.
Linkage of the ant genes
In the process of assembling male sterile facilitated recurrent selection
populations containing the ant alleles, crosses were made to a stock
containing the linked genes sex1 o msg6. In the resulting
populations ant13-13 has shown close linkage with this gene block.
A recombination value of P = 0.012 ± 0.011 between ant13-13
and sexl has been calculated. There were no crossovers between sex1,
o
and msg6 so the relative position of ant13-13 cannot be determined.
Such close linkage with sex1 would place ant13-13 very near
the centromere of chromosome 6.
Crosses with ant17-148 have shown no detectable linkage with the chromosome 6 marker genes. In crosses with the Pa7 gene for leaf rust resistance, a recombination value of P = 0.240 ± 0.061 has been found. The Pa7 gene has been located on chromosome 3 (Larkins, 1983). Further linkage studies are necessary to confidently assign the ant17-148 gene to this chromosome.
References:
Aastrup, S., H. Outtrup and K. Erdal. 1984. Location of the proanthocyanidins in barley grain. Carlsberg Res. Commun. 49:105-109.
Jende-Strid, B. 1976. Mutations affecting flavonoid synthesis in barley. Barley Genetics III. Proc 3rd Int. Barley Genet. Symp. Verlag Karl Thiemig, Munchen. p. 36.
Jende-Strid, B. 1978• Mutations affecting the flavonoid synthesis in barley. Carlsberg Res. Commun. 43:265-273.
Larkins, J.R. 1983. Location of genes conditioning resistance of barley to leaf rust. Plant Breed. Abstr. 83(10):756 (#8148).
von Wettstein, D., B. Jende-Strid, B. Ahrenst-Larsen and K. Erdal. 1980.
Proanthocyanidin-free barley prevents the formation of beer haze. MBAA
Technical Quarterly 17(1):1623.
