Dosage effect of Uq on the mutability pattern

Two types of mutability patterns are observed on kernels of the original source of the Uq controlling element system. One pattern type is distinguished by the appearance of relatively early and more frequent mutation events (larger and more numerous colored spots on a colorless aleurone background) and is designated coarse-high. A second type of pattern designated fine-low consists of later, infrequent events (relatively few small colored spots on a colorless aleurone background).

Progeny ears of the cross a1-ruq/a1-ruq +/+ x a1-ruq/a1-ruq Uq/Uq only contain kernels with a fine-low pattern of spots. In contrast, the reciprocal cross gives progeny with almost exclusively coarse-high spotting. Selfs or sibs of plants with the genotype a1-ruq a1-ruq Uq/Uq again contain almost exclusively coarse-high spotted kernels. These data when correlated with the origin of the endosperm (female parent, 2 doses; the male parent, one dose to the triploid endosperm) indicate the following:
Aleurone genotype Uq dose Observed spotting pattern
a1-ruq/a1-ruq/a1-ruq Uq/+/+ 1 fine-low
a1-ruq/a1-ruq/a1-ruq Uq/Uq/+ 2 coarse-high
a1-ruq/a1-ruq/a1-ruq Uq/Uq/Uq 3 coarse-high

Visually, no consistent difference is observed between the coarse-high spotting pattern with 2 doses of Uq versus 3 doses of Uq. No dosage effect has been observed when the Uq dose is held constant and the dosage of a1-ruq is varied, i.e., a1-ruq at 1, 2 or 3 doses.

Peter D. Friedemann and Peter A. Peterson

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.

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