Degree Type


Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Michael Lee


In this investigation, restriction fragment length polymorphisms (RFLPs) were used to construct a genetic linkage map for sorghum and to map quantitative trait loci (QTL) controlling morphological characteristics. For both purposes, an F[subscript]2 population from a cross between Sorghum bicolor subspecies bicolor (CK60) and Sorghum bicolor subspecies drummondii (PI229828) was used;The map consists of 201 loci distributed among ten linkage groups covering a distance of 1530 cM, with an average eight cM between adjacent loci. Maize genomic clones, maize cDNA clones, and sorghum genomic clones were used to identify the loci. Comparison of sorghum and maize maps revealed a high degree of homology, linkage order, and similar genetic distance. Most often a sorghum linkage group contains loci that map to two maize chromosomes. Frequently, these two maize chromosomes share considerable DNA duplication;For QTL identification, 152 unselected F[subscript]2 plants were evaluated. Interval mapping identified a total of 43 QTL, four for plant height, four for tillering, three for leaf length, two for leaf width, three for stalk circumference, two for maturity, six for panicle length, five for seed-branch length, two for sterile portion of the seed-branch, six for peduncle diameter, three for number of seed-branches per panicle, and three for seed weight. For each QTL, the most likely map position, magnitude of effects, gene action, and the source (progenitor) of alleles that increased the trait mean were described. Eighty-one percent of the QTL were placed into four linkage groups;Collectively, the QTL for each trait explained from 26% (in leaf width) to 69% (in panicle length) of the total phenotypic variation. Gene action was specific for each QTL. However, for most traits additive to partial dominance was the prevalent gene action (70% of the QTL). For alleles that increased the trait mean, most (70% of the QTL) came from the parent of higher phenotypic mean;QTL for plant height and for maturity may correspond to loci previously identified by alleles with qualitative effects. Also, QTL for plant height may correspond to QTL previously reported for the same trait in the maize genome.


Digital Repository @ Iowa State University,

Copyright Owner

Messias Gonzaga Pereira



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File Size

180 pages