II.1. The possible use of mo-type mutant in hybrid barley production.
H. Ahokas. Department of Genetics, University of Helsinki, P. Rautatiekatu 13, SF-00100 Helsinki 10, Finland.
A spontaneous stiff-strawed mutant with some tendency towards pistillody or multiovarism was observed in Pirkka variety in 1965 and was called HA 21. If the pistillody could be induced at will to manifest perfectly, the mutant could be used for hybrid seed production as the female parent.
During the past three years, there has been a search for a feminizator, a compound capable of induced femaleness in the androeceum. It must be easier to promote the femaleness in this labile mutant than in a normal variety. In the preliminary trials several compounds have been sprayed on microplots of HA 21. They were controlled by the original variety Pirkka, and by the application of HA 21 with the surficant only (Tween 20, 0.1 percent), plus the solvent, if needed. In 1972, the sprayings were done at 5-6 leaf-stage, and usually repeated three days later. The rate of the application has been approximately 1 ml/dm2. Most of the concentrations have been slightly phytotoxic or morphogenetic. In 1972, the following compounds gave a negative result as a feminizator: 6-benzyladenine (2000 ppm); 2-chloroethylphosphonic acid (Ethrel) (2000 ppm); 2-chloroethyltrimethylammonium chloride (10000 ppm); 2-chloro-9-hydroxyfluorene-9-carboxylic acid, methylester (Morphactin) (250 ppm); naphthaleneacetic acid, Na-salt (100 ppm); phenylboric acid (2000 ppm); DL-alpha-tocopherolacetate (500 ppm); 2, 3, 5-triiodobenzoic acid (1000 ppm). Morphactin was sprayed once; the other twice. Most of the compounds have been shown to interfere with the expression of sex in one or more plant species, many even inducing pistillody.
A high male-sterility in Pirkka, and a 100% male sterility in HA 21
were obtained by spraying twice with a mixture of gibberellins (GA3
200 ppm, and GA 50 ppm). In Pirkka the sterile anthers retained their morphology.
The sterility in HA 21 was due to pistillody. While Pirkka grew tall, HA
21 remained short, obviously slightly shorter than the HA 21 control: GA-treated
average = 64.5 + 1.69 cm; control average = 70.4 +
1.80 cm (measured to the spike basis); t = 2.378x,
P < 0.25 for the two-tailed test.
The possible negative effect on the height and the feminizing property of GA were surprising. Gibberellins have almost exclusively been found to promote maleness in different plant species, but only in few studies to promote femaleness (Nickerson 1959, Shifriss 1961, Bose and Nitsch 1970, Kubicki and Potaczek 1972, Sawhney and Greyson 1972).
The mo-type mutant might be profitable for hybrid barley production, because (1) the expressivity of the mutant is not complete, at least in Finland, and the stocks could be maintained by selfing, (2) the male-sterility could be induced at will in the crossing field by spraying the rows of the seed parent carrying the male-sterile gene with a feminizator (or in an ideal case, even treating the seeds before sowing them), and (3) mo-type mutant is a recessive that does not appear in the phenotype of the F1. Evidently, some of the stiff-strawedness of HA 21 can be found in the F1 plants. Hope for a suitable feminizator is good, because occasional pistillody has been proposed to be controlled by external factors, especially by photo- and thermoperiodical ones.
References:
Bose, T. K. and J. P. Nitsch. 1970. Physiol. Plant. 23:1206-1211.
Kubicki, B. and H. Potaczek. 1972. Genet. Polon. 13:67-74.
Nickerson, N. H. 1959. Ann. Mo. Bot. Gard. 46:19-37.
Sawhney, V. K. and R. I. Greyson. 1972. J. Amer. Soc. Hort. Sci. 97: 589-590.
Shifriss, O. 1961. Science 133:2061-2062.
E. Merck (Darmstadt) and Oy Suomen Gullviks Ab are thanked for a sample of Morphactin and Ethrel, respectively. The study was in part supported by Suomen Kulttuurirahasto.