GrainGenes
A Database for Triticeae and Avena
Hernandez-Soriano and Ramage, p. 20-21
II.12 Induction of haplo-viable mutations linked with the msg2 locus.
J. M. Hernandez-Soriano and R. T. Ramage. Department of Agronomy and Plant Genetics, University of Arizona, Tucson, Arizona 85721, USA.
Mutants that are transmitted through gametes of one sex and that are not transmitted through gametes of the other sex are termed "haplo-viable" mutants. Stadler (Missouri Agr. Exp. Sta. Bull. 204: 3-29, 1933) described haplo-viable mutants as being intermediate in genetic behavior between typical deficiencies, wholly eliminated in the gametophyte generation and typical mutations which are transmitted without loss by both gametophytes.
Haplo-viable mutants that are transmitted through the egg and are not transmitted through the pollen may be used to produce female parents of hybrid barley. If such a haplo-viable mutant is closely linked in repulsion with genetic recessive male sterile and seedling lethal alleles, it can be used to produce female parents in the same manner as that described for balanced tertiary trisomics (Ramage et al., Barley Newsletter 15: 73-78, 1972). When such plants are selfed, they set seed that will produce about one normal plant to one seedling lethal. Most of the pollen produced by the normal plants will carry the male sterile and seedling lethal alleles.
Tightly linked genetic recessive male sterile and seedling lethal alleles have already been produced. This communication reports progress made in the induction of haplo-viable mutants.
A haplo-viable mutant is recognized by upset genetic ratios of alleles linked with the mutant. A stock in which haplo-viable mutants could be recognized was established by crossing the translocation T2-7d onto male sterile, msg2, plants. T2-7d carries the dominant Msg2 and the recessive elongated outer glume, e, alleles and the male sterile plants carry the recessive male sterile msg2 and the dominant E alleles. Both loci are very closely linked with the break-point of T2-7d. The F2 of this cross should segregate one homozygous T2-7d plant, which would be male fertile and have elongated outer glumes : two heterozygous T2-7d plants which would be semisterile, male fertile and have normal glumes : one homozygous normal which would be male sterile and have normal glumes. Plants homozygous for either homologue can be easily identified.
The F1 of the cross was grown to increase the seed stock. Over 32,000 F2 seeds were treated with a 0.01 M solution of diethyl sulfate. The treated seed was planted at Bozeman, Montana in the summer of 1973. Over 10,000 heterozygous plants, identified because they were semisterile, male fertile and had normal outer glumes, were harvested. They were planted in plant rows in Arizona in the winter of 1973-74. The M2 rows were scored for chlorophyl mutants to obtain a measure of mutation efficiency. Approximately 18 percent of the rows segregated for albino seedling and 12 percent segregated for other seedling mutants such as xanthas, virescents, light greens, etc.
At flowering time, the rows were scored for absence, or near absence, of plants exhibiting elongated outer glumes. A few plants from rows exhibiting few or no plants with elongated outer glumes were crossed onto normal male sterile plants with normal outer glumes. The crosses and their male parents were grown in Montana in the summer of 1974.
About 20 lines had crossed and selfed progenies indicating the presence of a haplo-viable mutant linked with the Msg2 locus; i.e., the crossed progenies were mostly male sterile and the selfed progenies contained about one semisterile to one male sterile plant. Additional crosses were made between potential haplo-viable plants and normal male sterile plants. Crosses and their male parents are now being studied as to their breeding and cytological behavior.