PARENT SESSION
Tuesday, August 8, 5:00-6:30 pm
Poster Session 10 - Genetics, evolution, and paleoecology
Exhibit Hall, Ballroom Level, Cook Convention Center

Genetic architecture of leaf ecophysiological traits in Helianthus.

Brouillette, Larry^*,1, Rosenthal, David², Rieseberg, Loren³, Donovan, Lisa¹, ¹ University of Georgia, Athens, GA² Portland State University, Portland, OR³ Indiana University, Bloomington, IN

ABSTRACT- We investigated quantitative trait loci (QTL) for several leaf chemistry traits in early generation hybrids between Helianthus annuus and H. petiolaris, the parental species of the ancient homoploid hybrid sunflower species H. anomalus, H. deserticola, and H. paradoxus. We grew individuals of a second-generation backcross (BC2) toward H. petiolaris under optimum conditions in a glasshouse experiment. Trait values were measured once for each individual. In addition, a 96-marker genotype was determined for each individual using mapped SSR and AFLP markers, and significant QTL were detected using composite interval mapping. We identified QTL for leaf carbon concentration, leaf nitrogen concentration, leaf carbon to nitrogen ratio, leaf nitrogen per unit area, and photosynthetic nitrogen use efficiency. Leaf carbon isotope discrimination (13C) and leaf nitrogen isotopic composition (15N) were analyzed, but no significant QTL were found for the traits. Interestingly, two neighboring loci explained a relatively large percentage of the variation in leaf nitrogen per unit area. This was remarkable because the leaf nitrogen has been shown to strongly affect the fitness of early generation sunflower hybrids in the H. anomalus habitat, and traits controlled by few genes of large effect are expected to respond relatively quickly to selection. We speculate that the genetic architecture underlying leaf nitrogen may have facilitated the colonization of active desert sand dunes by H. anomalus.

Key words: evolution, leaf chemistry, quantitative trait loci