II.34 Usefulness of grandpa mutants.
T. Tsuchiya, Agronomy Department, Colorado State University, Fort Collins, Colorado 80521, U.S.A.
Grandpa (gp) is a mutant with good diagnostic traits: at early seedling stages showing white streaked leaves and at heading time showing a white streaked flag leaf and white spike and awn. This gene (gp) has been located in the long arm of chromosome 2 (Matchett, 1968) and will be used as a good marker. However, it grows very slowly and the typical white streaked traits of leaves disappear during the growing period from tillering to just before heading time, particularly under growing conditions with a high temperature.
A grandpa-type mutant was induced by radiation in the variety Montcalm. The gene was given the symbol gp2 and was said to be located on chromosome 6 (Walker et al., 1963). Matchett (1968) has found that gp2 is allelic to gp by allelism test. This finding was confirmed by Tsuchiya (1971) by allelism test of reciprocal crosses between gp and gp2 plants. Trisomic analyses using primary trisomic for chromosome 6, Purple, and telotrisomic for Telo 2L gave conclusive evidence of the location of gp2 in the long arm of chromosome 2.
It is, therefore, now clear from the above-mentioned results that the gp2 is allelic to gp. Probably because of a different genetic background, the plants homozygous for gp2 grow much better and faster than gp homozygotes and show typical white streaks or albino leaves, at least at early seedling stage. The flag leaf, the second leaf from the top, and the spike characters including the awn are all very similar to gp plants.
The present writer recommends the use of the gp mutant from the
variety Montcalm for genetic studies using gp as a marker gene.
Reports II.29 (P. 58) through II.39 (P. 66) by T. Tsuchiya and coworkers are based on the results of researches supported partly by NSF Research Grant GB 4482 X.