II. 41 Variation in the diagnostic character expression in five white streaked mutants in barley.
T. Tsuchiya, Department of Agronomy, Colorado State University, Fort Collins, Colorado 80523, U.S.A.
In his previous notes the author reported that the genes controlling white streak character in four white streak mutants are allelic to wst in a strain C.I. 11767 (U.S. 163) (Tsuchiya, 1972). During further experiments with these mutant strains, it was found that the diagnostic character expression and breeding behavior of these five mutant types are different in different strains.
1. Segregation of albino seedling in the progenies. All seven white streak mutants segregate various frequencies of albino seedlings in the selfed progenies. The frequencies of albino seedlings in the selfed progenies of five types are given in Table 1.
The percentage of albino seedlings are related to the albino area in the spikes (and leaves) of the parental plants. The frequencies of the albino varied not only from one strain to another, but also varied in different plants in a strain or even different spikes in the same plant.
The mechanism of the strange breeding behavior has been discussed by several workers such as Imai (1928), Arnason and Walker (1949), Hageman and Scholz (1962), and Takahashi and Moriya (1969). The important characters with these mutants are: (1) segregation of albino in the progenies of selfed white streak plants and of crosses in which the white streak plant is used as female, and (2) no albino segregation is observed when white streak is used as male in crosses. Since most of the albino seedlings are lethal, the F2 results from the crosses in which white streak mutant was used as the female will be somewhat complicated in some crosses. If the white streak mutants were used as male parents in the cross, there will be no problem, because cytoplasmic inheritance of albino character is not effective in this cross (Takahashi and Moriya, 1969).
2. Description of diagnostic characteristics of each mutant. The first two strains (C.I. 11767 and 11766) are very similar to each other in their characteristics with very fine and short white streaks distributed all over the leaves, sheaths and spikes. The record shows that these two strains were actually the same stock; the one was derived from the other, and the two are only different in black (B) and white (b) lemma and pericarp. The frequency of albino seedlings is very low. The expression of white streak character of the third stock (T18-19) is very similar to the first two lines just mentioned. Leaves are green with many fine white streaks distributed evenly all over the leaves. Wide white stripes have not been observed in leaves of this stock.
The last two stocks, white streak 3 (wst 3 is proved to be allelic to wst) and Caldecott's streak showed very similar character expression with larger (wider and longer) and more white sectors scattered all over the plants. Some spikes and tillers are almost completely white. Corresponding to wide area of albino sectors, the frequency of albino in the selfed progeny is much higher than the other three strains (Table 1). The results showed that even if the major gene is the same the character expression is different in different stocks with different genetic backgrounds.
References:
Arnason, T.J. and G.W.R. Walker. 1949. An irreversible gene-induced plastid mutation. Can. J. Res. 27: 172-178.
Hageman, R. and F. Scholz. 1962. Ein Fall geninduzierter Mutationen des Plasmotypus bei Gerste. Züchter 32: 50-59.
Imai, Y. 1928. A consideration of variegation. Genetics 13: 544-562.
Takahashi, R. and I. Moriya. 1969. Inheritance and linkage studies in barley. IV. Linkages of four variegated mutants. Ber. Ohara Inst. landw. Biol., Okayama Univ. 15: 35-46.
Tsuchiya, T. 1972. Allelism testing of various mutations in barley. BGN, 2: 80-87.
