CyToGENETIC EVIDENCE 
The conception of Tripsacum as an amphidiploid of 
wild maize and Manisuris originated from the rather sur- 
prising results of a segregation of Tripsacum chromo- 
somes from a hybrid of 7 dactyloides with a unique 
multiple tester stock of maize which has recessive marker 
genes on seven chromosomes (1, 2, 8, 4, 7, 8, 9). This 
“WMT” stock of maize was developed by Mangelsdorf 
some years ago expressly for the purpose of crossing with 
Tripsacum. Its development started in Texas on a back- 
ground of the variety ‘‘Mexican June.’’ Later, after 
being moved to Massachusetts where earlier maturity 
proved to be necessary, germplasm from two northern 
inbreds, P39 and A158, was added. The original hybrid 
of 7. dactyloides with this multiple tester was actually 
produced on a vigorous line cross between two inbred 
strains of the WMT stock. The principal purposes in 
making this hybrid with Tripsacum were: (1) to deter- 
mine whether T'ripsacum carries dominant alleles of the 
maize recessives; (2) to determine whether Tripsacum, 
having almost twice as many chromosomes as maize, 
carries the dominant alleles in duplicate in some cases; 
(3) to identify cytologically the Tripsacum chromosomes 
which carry the dominant alleles. 
A hybrid plant, obtained by the embryo culture work 
of Dr. Hager, exhibited none of the seven recessive 
characters introduced from maize but proved to be com- 
pletely sterile. Consequently, colchicine treatment to 
double the chromosome number was required in order 
to produce a tetraploid hybrid. This proved to have only 
about 50 per cent female fertility (Galinat, 1961), al- 
though virtually full female fertility of the Fy on the 2n 
level occurs in maize-Tripsacum hybrids involving 
another species, 7. floridanum (Galinat, 1962). Back- 
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