Only slight progress can be reported at present in the haploid studies. The problem of recognizing haploid plants in the seedling stage has proved to be much simpler than doubling the chromosome number in such plants (using colchicine as soon as the plants are tentatively identified). However, a homozygous diploid stock has been obtained from a Golden Cross Bantam haploid which was effectively doubled in a sector of the ear and tassel.
A few of the untreated or undoubled haploid plants set a seed or two when self‑pollinated. In order to obtain pollen from these plants it was necessary to open the anthers manually.
Two types of genetic testers have been used to locate naturally occurring haploids; these are Randolph's brown, liguleless stock (a B Pl C R lg) and several purple plumule (Pu) stocks (38‑11, Minn. 385A, Stadler's extract from Minn. 385A, etc.). The brown, liguleless tester has been more satisfactory than the purple plumule testers though on some seed stocks these do (as was hoped) permit a rough classification of the embryos in the dry kernels.
At present I am trying to develop better testers, particularly Pu testers, and am also checking the seedling characters of a number of stocks from which I would like to obtain haploids. I am also interested in the possibility of asexual increase of maize. Such increase of individual haploid plants before colchicine treatment would greatly increase the chances for effective doubling of a given haploid.
One kernel with twin embryos (side by side) was found in which one twin was haploid, the other diploid. On this account a number of other side by side twin embryos were grown out and either selfed or sibbed. No twins have been located in the seed crop of these plants.
Sherret S. Chase