Most of the symbolized mutants (i. e. mutants which have been assigned a permanent gene symbol) in the Maize Genetics Cooperation � Stock Center collection have known chromosomal locations. However, a small set of symbolized mutants were either never placed to chromosome, or had conflicting mapping data. This past spring, we selected a subset of the symbolized unplaced mutants, and placed them in our summer crossing nursery to be crossed by a comprehensive set of B-A translocations (TB's). The mutants for which we obtained positive results are summarized in Table 1. Additional crosses with linkage markers will be made to confirm chromosome arm placement, and allelism tests will be conducted with mutants with similar phenotype located on the same chromosome arm.

Table 1. Results of TB tests of symbolized unplaced mutants.
 

Mutant	Arm-locating TB Cross	Number of Positive Tests/Total Number of Crosses with this TB	Mutants on Same Chromosome Arm with Similar Phenotype	Note
l3	TB-6Lc	1/4	l10, l12, l15
l4	TB-7Sc	1/2	w17	1
oro2	TB-1Sb-2L(4464)	2/4
pb4	TB-5La	2/2	grt1, ppg1	2
v13	TB-5Sc	2/2
vp10	TB-10L(19)	2/3	vp13
vp12	TB-5La	2/4	lw2	3

1. All Coop stocks of l4 have an albino seedling phenotype, not a luteus phenotype.

2. Previously reported on 6L. This author found some stocks previously thought to be pb4 were in fact pb1, an allele of y1, located on 6L. Perhaps this is where the mapping confusion arose.

3. Previously reported on 6L (Araujo et al., Brazilian J. Genet. 20:71-74, 1997).

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