II.47 Genetic studies of two mutations by means of primary trisomic analysis.
T. Tsuchiya and J.V. Alanko, Department of Agronomy, Colorado State University, Fort Collins, Colorado 80523. U.S.A.
Even though many genes have been located in seven chromosomes, many more good genes are necessary to improve linkage maps of barley. Two mutant genes, male or ovaryless (ov1) (Tsuchiya, 1969) and yellow streak 3 (yst 3) (Tsuchiya and Singh, 1973) are good markers with easily recognizable traits and are viable in homozygous conditions. Trisomic analysis was used to associate these genes to respective chromosomes.
Trisomic plants of variety Shin Ebisu 16 (SE 16) (Tsuchiya, 1967) were used as female in crosses with the mutant plants. Combinations of crosses were shown in Table 1 together with the segregation ratios in F2 generation.
Table 1. Cross combinations between trisomic types and two mutant types and F2 segregations.
Yellow streak 3 (yst 3) is the mutant found in the variety Lion. The gene yst 3 is monofactorial recessive and not allelic to yst or yst 2 (Singh and Tsuchiya, 1973).
The gene yst 3 showed in F2 from cross between Slender (Triplo 2) X yst 3: (1) deviation from 3:1 ratio (X2 = 10.70), (2) good fit to 8:1 ratio in 2x portion, and (3) no recessive homozygotes in 32 plants in 2x + 1 portion. These results indicate that yst 3 is associated with chromosome 2. Similarly the Vv alleles showed trisomic ratio with chromosome 2 confirming the previously established results (Singh, 1974).
On the other hand yst 3 showed disomic ratio (Table 1) in F2 from the crosses of Pale (Triplo 3) X yst 3, Triplo 5 X yst 3 and Triplo 7 X yst 3. In F2 population from cross between Triplo 7 and yst 3 there was no recessive homozygote in 2x + 1 portion. However, the segregation in 2x portion (47:12) fit well to 3:1 ratio, and the segregation in 2x portion does not fit to a trisomic ratio of 8:1. Thus it seems to be safe to conclude that the gene yst 3 is not associated with chromosome 7.
Male or ovuleless is the X-ray induced mutant in the variety Kanto Bansei Gall and monofactorial recessive (Tsuchiya, 1969).
The gene ov1 for ovuleless or male were tested with Robust or Triplo 4. The results show conflict; total population and 2x portion showed good fit to disomic ratio of 3:1, but no recessive homozygote was observed in the trisomic portion. Since the number of plants was only 47 in this population, the conclusion whether the segregation is disomic or trisomic should be given after more plants are studied (see Tsuchiya et al 1976, BGN 6:95).
References:
Singh, R.J. 1974. Cytogenetics of telotrisomics in barley. Ph.D. thesis, Colorado State University, Fort Collins, Colorado. Mimeo. pp. 112.
Singh, R.J. and T. Tsuchiya. 1973. Allelism testing among three yellow streak mutants. BGN 3: 54-55.
Tsuchiya, T. 1967. The establishment of a trisomic series in a two-rowed cultivated variety of barley. Can. J. Genet. Cytol. 9:667-682.
Tsuchiya, T. 1969. Characteristics and inheritance of radiation-induced mutations in barley. Induced Mutations in Plants. (IAEA/FA0) : 573-590.
