Degree Type


Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Michael Lee


In general, maize, especially germplasm from the tropics and subtropics, is sensitive to photoperiod. This sensitivity hindered the exchange of germplasm between latitudes. To identify quantitative trait loci (QTL) associated with the response to photoperiod, a population of 236 F3 lines produced from a cross between a photoperiod-sensitive line CML9 and insensitive inbred A632Ht was used. These F3 lines were evaluated in three long and three short-day environments, in adjacent fields using artificial light, and in fields located in different latitudes, Mexico and Iowa. Days from sowing to anthesis (DTA), final leaf number (FLN) and plant height (PH) were measured. For each of these traits, photoperiod response (PPR) was estimated as the difference between the trait in long- and short-days divided by the trait in short-days. Composite interval mapping was used to detect QTL for each trait and comparison of locations of QTL detected in different daylengths for the same trait and for different traits were examined. A unique set of QTL was detected for each photoperiod and for each trait. One QTL for DTA, three QTL for FLN and four QTL for PH were detected in the same genetic regions in both daylengths. Five QTL for DTA, four QTL for FLN and three QTL for PH were detected only in long-day environments. Nine QTL for DTA, five QTL for FLN and three QTL for PH were detected only in short-day environments. QTL for photoperiod response were detected on four chromosomes for PPRDTA , on three chromosomes for PPRFLN and on three chromosomes for PPRPH. Chromosomes 2, 3, 4, 5, 6, 8, 9, and 10 had a cluster of QTL for different traits. This might suggest a common initial mechanism with subsequent specific pathways that regulate different traits.



Digital Repository @ Iowa State University,

Copyright Owner

Rkia Moutiq



Proquest ID


File Format


File Size

140 pages