Behavior of diploid lines derived from haploids.

Burdick, A. B.

I originally had four haploies in my collection, the two listed, Hap. D-y and Hap. pimpinellifolium, as well as a very old Hap. d\1\ and a recent Hap. San Marzano ms. The Hap. d\1\ and Hap. SM ms were lost in my collection but I believe Dr. J. B. Griffing at Iowa State still has Hap. d\1\ and Dr. J. A. Jenkins at the University of California, Berkeley, has Hap. SM ms. I have diploid progeny from each of these except the San Marzano haploid.

In 1945 I took 12 cuttings of Dr. E. W. Lindstrom's Hap. D-y and decapitated them in order to get callus growth. When shoots appeared I pruned off all but one on each of the 12 and allowed it to go on and set fruit. Eight of the twelve produced seed and these are numbered 001 through 008 in my stock list.

In 1948 a few plants of each of these eight stocks were set out in the field. The following data were obtained:

Stock No.    No. Plants     Fruit Skin Color (No. of Plants)
                             Yellow (Y-)      Colorless(yy)
001              26                                26
002              1                                 1
003              2                     1           1
004              1                                 1
005              3                     3
006              2  (lost)
007              4                                 4
008              7                                 7
Recalling that the original haploid was y, colorless skin, it is hard to explain the appearence of yellow skinned fruits in these doubled haloids. Other plant characters gave some indication of segregation also.

This apparent segregation from doubled haploids has led to further investigation with such lines. The pimpinellifolium haploid was doubled in 1949 and chromosome counts were taken on 100 randomly selected shoots. About half of these shoots were haploid, 24 were diploid, and the rest included periclinal chimaeras of 12-24, 24-48, and 12-48 chromosome numbers, three 13 chromosome haploids, four tetraploids, and one octaploid. Attempts are now being made to determine what morphological differences, if any, exist within and between these "homozygous" pimpinellifolium diploids.