II. 35. Progress in the production of aneuhaploid plants by using hap gene in barley.(1)
T. Tsuchiya and Azizeh Shahla, Department of Agronomy, Colorado State University, Fort Collins, Colorado 80523.
Original plan for producing aneuhaploid plants in barley was the use of H. bulbosum in crosses with various trisomic types. However, with the finding of a gene for haploid initiator mutant (hap) by Hagberg and Hagberg (1981), the plan was changed to use this gene, hap, in inducing aneuhaploid barley.
Since all trisomic lines in barley at Colorado State University are in the SE 16 background, introduction of the gene hap to S.E. 16 stock was initiated. The process involves completing 5 or 6 backcrosses to produce the hap/hap homozygote in S.E. 16 background.
To obtain some preliminary information on aneuhaploid barley, a hap/hap plant was crossed with Triplo 7S pollen. The F1 Triplo 7S which had hap cytoplasm and heterozygous for hap gene was crossed with the hap/hap homozygote. The Triplo 7S plants in BC1 were expected to segregate in +/hap vs. hap/hap = 1:1. The progenies of a total of 24 Triplo 7S of BC1 were cytologically studied with the results shown in Table 1.
The results shown in Table 1 were rather unexpected compared to the results reported by Hagberg and Hagberg (1981). It was expected that approximately 50% of the BC1 generation would segregate haploid (2n=x=7) and aneuhaploid (2n=x+l=7+1 telo 7S) and the total of these haploids were 15 to 40%, because these plants were supposed to be hap/hap homozygote.
As shown in Table 1 only 4 (16.7%) out of 24 populations segregated some haploid plants; the remaining 20 populations consisting of 388 plants contained no haploids. In some populations the number of plants studied was low with as few as 10 plants. However, this small number should not be critical in finding haploids, because in the original hap/hap stock, 3 haploids were found in a population of 14 plants (Tsuchiya, unpublished).
The average frequency of haploids (2n=7 and 7+1 telo 7S) in a total of four populations in which haploids were found was 3.11% which was equal to that in the progenies of heterozygotes for hap (+/hap). Hagberg and Hagberg (1981) consistently obtained 10 to 22% haploids in the homozygous condition. Probably these authors used the same genotype for the +/+ plants as the mutant type in their crosses. Genetic background may have an effect on the frequency of haploid plants even in the homozygous condition.
The results of this experiment suggest that the genetic nature of the gene hap may be rather complicated.
The aneuhaploid plant (2n = 7+1 telo 7S) seems to be less vigorous than the haploid with 2n=7 chromosomes. At present, only quantitative aspects of the four chromosomal types (2n=14, 14 + 1 telo 7S, 7, 7 + 1 telo 7S) are available. Qualitative characteristics of these four types and possibly plants with 2n = 14 + 2 telo 7S will be obtained in the near future.
References:
Hagberg, A. and G. Hagberg. 1980. Hereditas 93:341-343.
Hagberg, G. and A. Hagberg. 1981. Barley Genetics IV:686-689.
