Hybridization Between Amaranthus Tuberculatus and Amaranthus Hybridus

Interspecific hybridization can be thought of as a potential adaptive mechanism by which favorable alleles may be transferred among related species. Studies have shown that weedy Amaranthus species are capable of interspecific hybridization, and hybridization may foster the evolution of herbicide resistance. Yet, much remains unknown as to the dynamics of Amaranthus interspecies gene flow. The research presented in this dissertation addresses hybridization between two problematic Illinois weeds (A. hybridus and A. tuberculatus) and introgression at a herbicide resistance locus, ALS. The first chapter of the dissertation reviews the literature on the subject. The subsequent two chapters discuss the findings of a two-year field study aimed at assessing the potential for F1 production. In this study, field hybridization rates as high as 5.9% (A. hybridus as female) or almost 70% (A. tuberculatus as female) were obtained, and prezygotic reproductive barriers appeared to be limited mostly to pollen availability/competition. All F1 hybrids were dioecious and sex segregation was consistent with postulated chromosomal XY-type system, with males as the heterogametic sex. Chapter Four provides a morphological, reproductive and cytogenetic characterization of F1s. Although hybrids differed from parental populations in several morphological characters, these characters were not reliable, by themselves, for unambiguous hybrid identification. However, DNA content analysis was used successfully to discriminate F1s from individuals of the pure species. Hybrid sterility (hybrids attained 3.3% of the seed output of parental A. tuberculatus) also could be used as a discriminatory tool. Hybrid progeny upon backcrossing to the two parental species were profiled for fertility, introgression at ALS and genomic structure, and these data are presented in Chapter Five. Fertility in the BC1 generation was greater than that of F1s, and 3% of BC1S had seed output similar to that of the parental species. Fertility in the BC1 did not correlate (in a strict way) with reconstitution of parental genomes. Hybrid sterility appeared to be controlled by relatively few loci. Heterozygosity at ALS was negatively correlated with fertility. Linkage of ALS to a locus associated (directly or via epistasis) with hybrid sterility may explain the fertility penalty observed with ALS introgression.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Crop Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2005

Author dc:creator

• Trucco, Federico

Contributors dc:contributor

• Tranel, Patrick J.

• Biology, Genetics

Language dc:language

eng

Identifier

(MiAaPQ)AAI3182402

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/85022