The narrow leaf and plant stature mutant narrow sheath (ns) was identified by Elsing and Albertsen as a single factor trait which sometimes displayed non-Mendelian patterns of inheritance (MNL 66:49-50, 1992). Subsequent analyses have determined that, in the original inbred line in which the mutant was isolated, the ns phenotype is inherited as a single recessive factor trait (Table 1). However, in the inbred lines Mo17 and B73, and in our laboratory Mutator-active inbred stock, the ns trait displays duplicate factor inheritance (Table 2). In order to locate the ns duplicate factor pair to chromosome arm using the B-A translocation series (Kindiger and Beckett, MNL 60:43, 1986), plants heterozygous for each of the dual factors were crossed as female onto hyperploid heterozygotes. Hypoploid plants were selected among the F1 progeny on the basis of 50% pollen semi-sterility, and plant phenotype (where applicable). The F1 hypoploids were either self-pollinated or backcrossed to ns mutants. The ratios of ns vs. non-mutant seedlings scored in the progeny of these crosses are presented in Table 3. The data indicate that the ns duplicate factors are located on chromosome arms 3S (ns1) and 4L (ns2). Molecular markers are now being used to RFLP map the ns loci to more precise locations.
Table 1. Number of progeny obtained from self of normal plants generated
from ns x ns / + cross in original stock obtained from Pioneer
|Self #||Mutant No.||Normal No.||Total No.||Mutants (%)|
Table 2. Combined sum total of number of progeny obtained from selfs
of ns/Mo17 and ns/B73 plants.
|F1 genotype||Mutant||Normal||Total||Mutants (%)|
|Combined sum total||134||2002||2136||6.27|
Table 3. Summary of ns1 and ns2 TB mapping results
|TB parent||Hypoploid F1 plants (#)*||F1 cross||Total ns progeny (#)||Total progeny (#)||ns progeny (%)|
to the MNL 69 On-Line Index
Return to the Maize Newsletter Index
Return to the Maize Genome Database Page