Orsan/Wilson Hybrids, Inc.

Development of a tertiary trisomic (A A B-A) stock carrying indeterminate gametophyte (ig)

--Bryan Kindiger

The ig gene, first identified by Kermicle in 1969, is known to be a simply inherited single recessive gene. This gene allows the development of androgenetic monoploids at a frequency of 1-3%.

Utilizing the TB-3Ld B-A translocation in a W23 R-nj background, a tertiary trisomic (A A B-A) and of the genetic constitution ig ig B-A(+) has been generated. The breakpoint position of the TB-3Ld translocation is apparently close enough to ig to disallow frequent crossing over in the region.

Classical maintenance of the gene in the heterozygous condition yields only 21% ig/ig individuals (Kermicle, Amer. J. Bot. 58:1-7, 1971). Since homozygous ig individuals are male sterile, it is impossible to maintain them in a homozygous condition. By having ig in a tertiary trisomic stock, this may allow 40-50% regeneration of the ig/ig genotype and successful maintenance of homozygosity by selfing.

Transmission of the B-3Ld chromosome is 50% through the female and about 2% through the pollen. Chromosome counts of 31 root tips showed 14 with 20 chromosomes, 14 with 20 + 1 B-A, 1 with 10 chromosomes and 2 with 20 chromosomes + 2 B-A's. By utilizing the tertiary trisomic stock as male, about 98% of the gametes should carry the ig gene.

Seed of this stock is being supplied to the Maize Genetics Cooperation Stock Center.

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