abstracts of papers presented at the 1962 meetings - Genetics

992 ABSTRACTS
or heterozygote) which is not present in either parent. It can be demonstrated by agglutination
of the cells of the hybrid following absorption of antisera against the hybrid with erythrocytes
of both parental types.-Repeated backcrosses to Streptopeia risoria of species hybrids and selected
backcross hybrids from respective matings of chinensis, orientalis, and senegalensis with risoria
have resulted in the establishment of individuals essentially identical to risoria with the exception
of their content of a gene or genes from one of the other species for the antigen number 8: ch-8
(formerly called d-If), or-8, or se-8. The contrasting character of risoria is designated ri-8. The
cells of each of the three kinds of heterozygotes (ch8/ri-8, or-8/ri8, and se-8/ri-8) invariably
carry a hybrid substance peculiar to itself, but the respective homozygotes produced by inter se
matings do not.-Matings among the three homozygotes have produced two new combinations,
ch-8/se-8, and ch-8/or-8. The cells of each of the three combinations, ch-8/ri-8, ch-8/se-8, and
ch-8/or-8, possess a hybrid substance which is related to the others; but each contains antigenic
specificities peculiar to itself. Thus, it appears that different combinations of the causative genes,
or of genes linked to them, produce different interaction products.
VARMA. BASUDEO, ALAN CASPAR, and W. RALPH SINGLETON, Blandy Experimental Farm, University
of Virginia, Boyce, Virginia: Effect of chronic gamma radiation on proembryos of corn.
-During the summer months of 1960, corn plants of inbred Pr line which are susceptible to the
leaf spot disease of Helminthosporium carbonum were grown in pails. Twenty-four hours after
self pollination, they were moved into the gamma field and were irradiated for one day giving
a total dose of 1000r. In a few cases, ears showed poor seed settings. In the summer of 1961, all
the seeds obtained from irradiating at the proembryo stage were planted in the field and selfpollinations
were made. Mature plants showed differences in their height, abnormal growth
showing signs of chromosomal losses, pollen sterility, etc. In this spring F, seeds have been
tested in the green house for any mutations produced. In a number of cases it seems that gene
mutation have been induced. Seedlings have segregated for green and yellow-green characters
in a 3:l ratio. Another mutant observed is dwarf plants, which also segregated in a 3:l ratio.
These dwarf mutants died after 20-25 days. Other than these, albino, luteus and japonica type
mutants have appeared. The great frequency in the mutation rate produced by semiacute gamma
radiation at the proembryonic stage is worthy of notice. Work is in progress to test these F, seeds
for any resistance induced to Helminthosporium carbonum disease. Results will be discussed.
Complete data will be presented and the fundamental importance of these findings to radiation
genetics and plant breeding will be discussed.
VOGEL, H. J., Institute of Microbiology, Rutgers University, New Brunswick, N.J.: Lysine
synthesis in some ‘‘algal fungi” and blue-green algae: phylogenetic implications.-Among a
number of phycomycetes tested, those having either anteriorly uniflagellate or biflagellate ZOOspores
synthesize lysine via 2,6-diaminopimelic acid (DAP), whereas those having either posteriorly
uniflagellate zoospores or aplanospores produce lysine via 2-aminoadipic acid, as do
higher fungi and euglenids (VOGEL, Symposium on Evolutionary Biochem., Fifth Intern. Congr.
Biochem., Moscow, 1961). These studies carried out with the aid of diagnostic radiocarbon
tracers (3- and &labeled aspartic acids and l-labeled alanine) have now been extended to the
following phycomycetes with anteriorly uniflagellate or biflagellate zoospores: Rhizidiomyces
sp. (Hyphochytriales) , Thraustotheca clavata (Saprolegniales) , Sapromyces elongatus (Leptomitales),
Sirolpidium zoophthorum (Lagenidiales), and Pythium ultimum (Peronosporales) .
All these organisms, in line with the above-mentioned generalization, use the DAP-lysine pathway,
and thus participate in an evolutionary continuum which includes green algae, as well as
bacteria and vascular plants (VOGEL, op. cif.). Similar experiments have now shown that the
DAP-lysine pathway is also employed by the blue-green algae, Nostoc sp. and Plectomma
boryanum. (Aided by the National Science Foundation and the Office of Naval Research.)
WALTERS, MARTA SHERMAN, Santa Barbara Botanic Garden and University of California, Santa
Barbara, Calif.: A nuclear body in meiosis of Bromus.-A structure tentatively called a “nuclear