II.4 An induced albino mutation on chromosome 6.
D.R. Clark and R.T. Ramage. Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721, U.S.A. "R"
Seed produced by plants that were trisomic for chromosome 6 in the cultivar 'Betzes' were treated with the chemical mutagen 'diethyl sulfate' (DES). The treated seed were planted and seedlings that were trisomic for chromosome 6 were selected. Progenies of the selected trisomic 6 plants were grown and examined for the presence of mutations (Clark and Ramage, 1975. BGN 5:8).
Mutations that were found in ratios approximating 3:1 were considered to be located on a chromosome other than chromosome 6. Mutations that were found in ratios approximating 11 : 1 were considered likely to be located on chromosome 6. A ratio of 11 : 1 would be expected with chromosome segregation and 25% transmission of the extra chromosome if the mutation was located on chromosome 6.
Several M2 rows that contained mutations in an approximate 11 : 1 ratio were found. Trisomic and diploid plants from such rows were harvested and progenies from them were grown. The numbers and kinds of plants found in the M2, M3 and M4 generations of one albino seedling mutation are given in Table 1.
Diploid plants that were heterozygous for the mutation produced progenies containing approximately 3 green : 1 albino seedlings indicating that the mutation is a monofactorial recessive.
With chromosome segregation and 25% transmission of the extra chromosome, duplex trisomics are expected to segregate 11 green : 1 albino seedlings and simplex trisomics are expected to segregate 11 green : 7 albino seedlings. Plants that were trisomic for chromosome 6 produced progenies containing green and albino seedlings in ratios expected if the mutation was located on chromosome 6. As expected, both duplex and simplex trisomics were found in M4.
