P. axillaris and P. exserta differ in scent production and petal color. P. axillaris is white and heavily scented, whereas the intensely red flowers of P. exserta are devoid of scent. Two QTL for scent production of major effect were detected on chromosomes II and VII. ODO1, a MYB transcription factor, underlies the QTL on chromosome VII and current work is being carried out to isolate the gene underlying the QTL on chromosome II.

Moths Prefer Scented Flowers, Be They Red or White (A) Setup of wind tunnel, where pure, standardized air enters from the right in a laminar flow. (B) Choice experiments investigating preferences by the moth M. sexta for scented flowers. For each experiment, the proportion of the moths that made their first choice (white bars) and first proboscis extension (black bars) on scented plants (left) is plotted against unscented plant (right bars).