Rick, C. M.
Our material of this mutany traces to a single plant brought to us by a former student, Irwyn Rammer. It had attracted attention in a field of Pearson because it had a peculiar dwarf, stunted appearance. The plant which was potted and grown during the summer in the greenhouse at Davis, managed to survive, although its growth was very slow and foliage highly abnormal. The few flowers produced failed to set fruit an selfing but did yield viable pollen which permitted a crcss with normal Pearson.
When seedlings first emerged from this cross, part of them seemed to have all the symptoms of damping-off, despite control measures and healthy progenies growing in adjacent rows in the same flat. In spite of their short size, dark green and deeply furrowed cotyledons, they survived and it became apparent that their genotype, not disease, was at fault, for 13 seedlings had this abnormal appearance and 15 were normal, the difference between the two types being unmistakable. All progenies of such pedigree grown to date total 80 furrowed and 75 normal.
Furrowed plants in Pearson genotype remain stunted throughout their life cycle. Performance is generally much better in the field than in the greenhouse, but even the best plants we have seen are very much reduced with very short internodes and small leaves, which tend to bronze and the edges of which curl downward. Anthers usually appear normal, but corollas are greatly reduced and flowers never open properly. No fruits are set despite abundant pollen and frequent manual selfings. Viability of pollen is indicated by the good seed set obtained in crosses.
The above remarks apply strictly to furrowed in pure Pearson genotype; in hybrids with distantly related stocks growth is much improved at all stages and seeds can be produced by selfing, some fruit even setting naturally.
The pooled data from the progeny of various selfed hybrids is: 1263 furrowed, 806 normal. In addition to these two phenotypes, certain families yielded an eqxtreme grooved type, which failed to survive cotyledon stage. The totals of these families are: 488 extreme furrowed, 1154 furrowed, 735 normal. These data plus indication below of a strong linkage with tf provide fair evidence of a single gene with incomplete dominance, lethal when homozygous and semilethal when heterozygous. One family, in which conditions for emergence were excellent yielded. 211 Fw/Fw, 516 Fw/+, 253 +/+. Linkage tests are summarized as follows:
Combination X2
Fw-a Fw/+ + 84, Fw/+ a 15, +/+ + 53, +/+ a 18 2.5
Fw-ag Fw/+ + 84, Fw/+ ag 31, +/+ + 63, +/+ ag 14 0.7
Fw-bu Fw/+ + 84, Fw/+ bu 71, +/+ +113, +/+ bu 41 0.1
Fw-c Fw/+ + 84, Fw/+ c 13, +/+ + 51, +/+ c 20 5.5*
Fw-d Fw/+ + 84, Fw/+ d 13, +/+ + 54, +/+ d 14 4.2
Fw-dl Fw/+ + 84, Fw/+ dl 36, +/+ + 80, +/+ dl 29 2.7
Fw-e Fw/+ + 84, Fw/+ e 110, +/+ +220, +/+ e 33 7.6
Fw-l Fw/+ + 84, Fw/+ l 12, +/+ + 59, +/+ l 12 0.8
Fw-rv Fw/+ + 84, Fw/+ rv 17, +/+ + 31, +/+ rv 9 0.2
Fw-tf Fw/+ + 467, Fw/+ tf 49, +/+ + 62, +/+ tf 32 344.1**
Fw-yv Fw/Fw + 92, Fw/Fw yv 33, Fw/+ + 183, Fw/+ yv 32 4.2
(2 df)
+/+ + 78, +/+ yv 31
* ** Asterisks indicate significant indication of linkage.
Although many of the families deviate from normal ratios and the combination
with e gives a significant coupling value despite the cross having been made
in repulsion phase, the only sure-fire linkage is that with tf, for which the
estimate of crossing over is 11%.