In order to test for linkage between several dominant mutants, all of which have in common the expression of the various Rolled phenes, the following experiment was undertaken. Because previous attempts to generate homozygotes were not successful, known heterozygotes for each of several of the alleles were crossed to each other, generating families which segregated one of the two possible critical genotypes: either Rld1-O/Rld1* or Rld1-O/+, Rld2*/+. Each phenotypically Rolled plant in the resulting population was outcrossed to a +/+ tester. The resulting progeny were grown out and families not segregating 1:1 for the Rolled phenotype were analyzed. In addition to confirming the previously reported close linkage between Rld1-O (previously referred to as Rld-1990) and Rld1-1441 (S. Chao and M.G. Neuffer, MNL67:33), they revealed a very close linkage between two other mutations exhibiting the Rolled phenotype (Table 1). These will be referred to as Rld1-1608 and Rld1-MF. Contamination cannot be ruled out, therefore the map distances expressed may in fact be smaller.
 

Mutant pair	No. outcross progeny observed	No. exhibiting Rld phenotype	No. not exhibiting Rld phenotype	Map distance
Rld1-O, Rld1-MF	416	413	3	0.7
Rld1-O, Rld1-1441	438	437	1	0.2
Rld1-1441, Rld1-MF	90	89	1	1.1
Rld1-1608, Rld1-MF	115	115	0

Another mutation, Rld1-PB, showed no recombination with the linked polymorphism identified by the RFLP marker csu54 in 91 individuals genotyped, also indicating a very close linkage to Rld1-O. Based on this information we conclude that the five dominant Rolled mutants studied are likely to be alleles of rld1. 

Return to the MNL 70 On-Line Index
Return to the Maize Newsletter Index
Return to the MaizeGDB Homepage