II. 31. The linkage of the genes mo5* and n in barley.
* This symbol was not officially given (T. Tsuchiya).
O.T. Tazhin, Biological Faculty, Department of Genetics, Kazakh State University, Alma-Ata 480091, USSR.
There have been known four alleles of the gene "multiovary" which control the multiovary character in the florets of barley. When the mutants controlled by the alleles mo1-mo4 are pollinated artificially, more than one seed per spikelet is set. All the alleles are recessive and the characters, controlled by them, are inherited monofactorially (Kamra, 1966).
In 1964 we found in a sample of Revelatum 1886 (Mongolia) a plant with many ovaries which had appeared spontaneously. Revelatum 1886 belongs to the six-rowed barleys with hull-less seeds. Each of its florets has one ovary, three stamens and two lodicules. The mutant with many ovaries differed from it only by its floral structure. The mutant plant has four ovaries per flower (one ovary is the main one and the three others have developed from a stamen) and two half-curled up greenish leaflets in place of the two lodicules (Fig. 1).
Figure 1. The upper row: to the right - the organs of a normal flower (one ovary, three stamens and one of the lodicules); to the left - the ovaries of the mutant plant; The middle row: to the left - the main ovary; to the right - the three ovaries which developed from the stamens; The lower row: the two half-curled leaflets, developed from the two lodicules.
The crossing of this mutant plant with the normal plant, as well as the hybrid analysis, have allowed us to describe a new allele - the allele mo5, which controls monofactorially the multiovary character in barley florets. The allele mo5 conditions the transformations of the two lodicules into two leaflets, that of the three stamens into three nonfunctional ovaries, and that of the main ovary into a partially functional organ.
The initial mutant and the plants with many ovaries, which have appeared during the segregation of the hybrids in 1964-1972, were artificially pollinated with the pollen of var. Pallidum, Nutans and Nudum. In some combinations analysing crosses have been performed. In 1964-1972 there have been pollinated 10073 flowers and 302 hybrid seeds obtained which averages 3.33%. The hybrid seeds are small and in most cases are twisted. Their field germination rate does not exceed 70%. The Fl hybrids had in all combinations normal floral structure and a closed type of blossoming. Seed setting took place in every flower.
The six-rowed mutants were artificially pollinated with the pollen of var. Pallidum. This always resulted in F1 hybrids with hulled seeds, and F2 hybrids segregated into normal and multiovarious plants with the ratio 3:1. All normal plants were hulled with one exception. A single plant showed hull-less seeds.
The six-rowed mutants were artificially pollinated with the pollen of var. Nutans. This resulted in Fl hybrids with hulled seeds with the ear character of an intermediate type. The F2 hybrids segregated into plants with normal seeds (two-rowed, intermediate and six-rowed plants) and into plants with many ovaries (two-rowed, intermediate and six-rowed plants) with the ratio 3:1. All normal plants were hulled with one exception. A single plant showed hull-less seeds.
The two-rowed mutants were artificially pollinated with the pollen of var. Nutans. This always resulted in F1 hybrids with hulled seeds, and F2 hybrids segregated into normal and multiovarious plants with the ratio 3:1. All normal plants were hulled with one exception. For example, in 1973 one of such hybrids segregated into 1841 normal and 623 multiovarious plants. A single plant showed hull-less seeds.
The six-rowed mutants were artificially pollinated with the pollen of var. Nudum. This resulted in F1 hybrids with hulled seeds and F2 hybrids segregated into normal seed plants (two-rowed, intermediate and six-rowed plants) and multiovarious plants (two-rowed, intermediate and six-rowed plants) with the ratio 3:1. All normal plants were hull-less.
For lack of anthers in the flowers of the multiovarious plants there has been observed no self pollination and fertilization and no seeds have been set.
The multiovarious mutants carry the recessive gene n, which is linked with the recessive gene mo5. When such plants are crossed with the hull-less seed plants, F1 hybrids have always hull-less seeds and F2 hybrids segregate with the ratio 3 normal and hull-less plants and 1 mutant plant. In F1 hybrids the recessive character of hull-lessness is revealed because the multiovarious parents are homozygous and carry the same recessive gene of hull-lessness, the gene n, which var. Nudum does.
When the multiovarious plants are crossed with the hulled plants (var. Pallidum, var. Nutans), the F1 hybrids have always hulled seeds, and F2 hybrids segregate with the ratio: 3 normal and hulled plants and one mutant plant. The segregating single plant with hull-less seeds are crossover plants. On the basis of such crossover plants, occurring in F2, the crossing-over value between the linked genes mo5 and n is being determined.
The recessive genes mo5 and n are nonallelic genes. The first one conditions the multiovary character in the barley flowers, the second one conditions the hull-less character of the seeds. If these genes were situated in different chromosomes, they would condition the segregation, characteristic of the dihybrid crossing. Such segregation was not observed. In all combinations, the F2 from mutants X hulled plants segregated with ratio: 3 plants with normal and hulled seeds and 1 mutant plant as it takes place in the case of tightly linked inheritance of the two nonallelic genes.
There has not been found the linkage group for the gene multiovary; it is known, however, that the gene n is located in chromosome 1 (Moh and Nilan, 1953; Nilan, 1964; Kamra, 1966; Bakhteev, 1971).
Consequently, it may be concluded that the gene mo5, described by us and which is linked with the gene n, is located in chromosome 1 of barley.
Bakhteev, F.H. 1971. On the genetical basis of barley breeding. In: "The Genetical basis of plant breeding." Published by "Nauka", Moscow, p. 374-416.
Kamra, P. 1966. Genetic control of the development of floral organs in Hordeum vulgare. Mechanism of mutation and inducing factors. Proceedings of Symposium held in Prague in August 9-11, 1965, p. 213-215.
Moh, C.C. and R.A. Nilan. 1953. Multi-ovary in barley. J. Heredity, 44:183-184.
Nilan, R.A. 1964. The cytology and genetics of barley. 1951-1962. Monographic supplement N 3, vol. 32. N l,Washington State University, p. 96-117.
BGN 10 toc
BGN Main Index