II.20. The induction of morphological barley mutants having new specific and generic characters with the methods of radiation and chemical mutagenesis.
M. R. Kozachenko. Ukrainian Institute of Plant Industry, Plant Breeding and Genetics, Kharkov, U.S.S.R.
In trials on induced mutagenesis varied types of changes including morphological mutations filmy spring two-rowed barley vegetative and reproductive organs, have been obtained. Many types of morphological mutations lay out of the range of variety, subspecies or species to which the cultivars under study belong. The most interesting ones are such as: rudimentary awns or normal ones formed in underdeveloped side spikelets, short-awned, awnless, three-awned, smooth-awned, lamina-shaped awns, different ear densities (including erectoides), intermediate, ear two-rowed in lower part and six-rowed in upper end, six-rowed, mace-shaped, pyramidal, verticillate dwarf ear, semi-naked, naked, close occumbent segments of ear heart.
The possibility was also shown of inducing mutants or individual mutant characters that probably have disappeared at a certain stage of evolution and now do not occur within the genus Hordeum L. Very interesting in this respect are morphological mutations of culm, ear, kernel and generative organs of barley.
Some gamma-ray and chemical mutants were of unusual type having thin and naked seeds, like that of rye, wide possage from lemma to awn and tendency to open flowering.
A fairly extraordinary gamma-mutant with many nodes and leaves, and with tendency to branching with formation of additional spikes has been observed.
It is known that at the present time the spikelets in genus Hordeum L. contain only one flower, not like many-flowered spikelets of genera Triticum L., Secale L. and Avena L. of the same family Gramineae; these barley spikelets contain only one ovary and three stamens with two-chamber anthers. In this study mutants with a different number of ovaries and stamens in their flowers have been obtained through chemical supermutagen (N-nitroso-N-methylurea/NMU/ and N-nitroso-N-ethylurea/NEU/) and gamma-ray treatments.
We have observed five stamens instead of three in the flower of one gamma-mutant obtained in these experiments.
Four ovaries of nearly equal size (each bearing two plumose-shaped stigmas) per one flower have been observed within one of the chemical mutants (No. 71-1811-2, 0, 02 % NEU-treatment). The flowers of this mutant had no stamens. Only single seed formation has been observed with these plants.
In another chemical mutant (No. 71-1825-2, 0,02% NEU treatment) various number of stamens (3 to zero, as a result of their transformation into ovaries) and ovaries (1 to 4) have been observed. One can observe 1 to 2 or only 1 kernel and 1 ovary (spread in growing alike glumes of various sizes) per spikelet. Moreover, the additional glume formation (often with incipient awns) could be observed inside two lemmas in the barley spikelets.
One to three ovaries per flower have been observed in the third chemical mutant (No. 71-3056-10, 0,006 % NMU treatment). The stamens usually didn't form, and in case of their formation one of three stamens, as a rule, have been observed. The apparent transformation of stamen anthers into ovary bearing two plumose shaped stigmas, and filament transformation into a rudimentary glume has been observed. It has been found that only single seed formations occured in the spike; moreover, the formations of seeds could occur even in the spikelets that contained one stamen with normal anthers.
Three stamens and three (or two, as a minimum) ovaries (with two plumose stigmas on each ovary) per spikelet have been observed within the fourth chemical mutant (No. 71-2925-2, 0,05% NEU treatment). The additional ovaries were of smaller size, and each subsequent one has been developed in the vallecula of the preceding ovary. The intermediate ovary was the smallest, often underdeveloped to a great extent; sometimes it was completely absent. Between the first and the third (middle) ovary a rudimentary glume has been observed.
Perhaps, certain induced mutants could form 2 to 3 flowered spikelets containing additional ovaries and, particularly, floral glumes (i.e. the flower components) underdeveloped or weakly developed multiflorous gamma-mutant is of great interest in this respect. All these results enable us to suppose that a multiflorous effect was inherent at one time in those initial forms from which genus Hordeum L. had sprung up. The data obtained indicates the certain relationship between genera of Gramineae family which probably had the same initial form in their evolution. Therefore, obtaining and study of induced mutants that possess new generic characters may give the possibility of elucidating certain problems of phylogenesis and systematics of plants.
References:
Kozachenko, M. R. 1972. Mutation variability in barley as depending on chemical supermutagens, their concentrations, cultivar genotypes and realization of mutation in M1- and M2-plant ontogenesis. In: Nauchny trudy kharkovskogo otdeleniya VOGIS im. N.I. Vavilova. Kharkov, U.S.S.R. (In press).
Kozachenko, M. R. 1973. Increase barley induced mutability and extension variability by the way of similtaneous use of hybridization, mutagenesis and selection methods. In sb.: Selectia i semenovodstvo, v. 25. Kiew, U.S.S.R. (In press).