II. 42. Trisomic analysis of a mutant gene ovl for ovaryless or male in barley*.
Lindy Seip and T. Tsuchiya, Department of Agronomy, Colorado State University, Fort Collins, Colorado 80523, U.S.A.
*Supported in part by the USDA Research Grant 12-14-5001-265 to T. Tsuchiya.
The gene for male, or ovaryless (ovl) was first reported by Tsuchiya (1962). It has not been the subject of much genetic study, although a detailed description has been made (Tsuchiya, 1969).
This mutant is the result of irradiation treatments and was first found in the M3 generation. It is recessive or a weak form of incomplete dominance in which the heterozygote shows some mutant characteristics but is not always easily distinguished from the normal.
The homozygote of the ovl mutant has only rudimentary female organs while the anthers are completely normal with full pollen fertility. Other features include: a lack of midvein in the second and later leaves, leading to a definite drooping effect; poorly developed lemma; and lack of awns. The homozygous mutant is completely female sterile (Tsuchiya, 1959).
The heterozygote has full fertility but shows some drooping effect of leaves due to incomplete development of the midvein (the midvein extends approximately 75% along the leaf of a normal plant and only 55% of the heterozygous leaf).
The location of the ovl gene is suspected to be on chromosome 4 (Tsuchiya, 1969, 1972; Tsuchiya et al., 1976). To test this, crosses were made over a several year period between the primary trisomic for chromosome 4 (triplo-4 or Robust) and the homozygous male, ovl, plant. Due to the insufficiency of previous data (Tsuchiya et al., 1976), the current work was done to increase the population to be measured. The F2 seeds from the cross Triplo-4 x ovl homozygotes were germinated and the chromosomes were counted. The results are shown in Table 1.
Table 1. Segregation ratios in F2 populations of crosses between primary trisomics and male, ovl.
Results indicate that the ovl gene is most likely located on chromosome 4.
Current and future work includes confirmation of this data as well as telotrisomic analysis to determine the arm location of the ovl gene.
References:
Tsuchiya, T. 1962. Radiation breeding in two-rowed barley. Seiken Ziho 14:21-34.
Tsuchiya, T. 1969. Induced mutations in plants. International Atomic Energy Agency publication, p. 575-590.
Tsuchiya, T. 1972. Cytological identification of a translocation accompanied by a gene mutation. BGN 2:107-108.
Tsuchiya, T., S.D. Tanksley and R. Ward. 1976. Trisomic analysis of three mutant genes in barley. BGN 6:95-96.
