Research The genetic architecture of petal number in Cardamine hirsuta Bjorn Pieper, Marie Monniaux and Angela Hay Max Planck Institute for Plant Breeding Research, Carl-von-Linne-Weg 10, 50829 Koln,€ Germany Summary Author for correspondence: Invariant petal number is a characteristic of most flowers and is generally robust to genetic Angela Hay and environmental variation. We took advantage of the natural variation found in Cardamine Tel: +49 221 5062108 hirsuta petal number to investigate the genetic basis of this trait in a case where robustness Email:
[email protected] was lost during evolution. Received: 20 April 2015 We used quantitative trait locus (QTL) analysis to characterize the genetic architecture of Accepted: 4 July 2015 petal number. Αverage petal number showed transgressive variation from zero to four petals in five New Phytologist (2016) 209: 395–406 C. hirsuta mapping populations, and this variation was highly heritable. We detected 15 QTL doi: 10.1111/nph.13586 at which allelic variation affected petal number. The effects of these QTL were relatively small in comparison with alleles induced by mutagenesis, suggesting that natural selection may act Key words: Cardamine hirsuta, comparative to maintain petal number within its variable range below four. Petal number showed a tempo- development, natural variation, petal ral trend during plant ageing, as did sepal trichome number, and multi-trait QTL analysis number, quantitative trait locus (QTL). revealed that these age-dependent traits share a common genetic basis. Our results demonstrate that petal number is determined by many genes of small effect, some of which are age-dependent, and suggests a mechanism of trait evolution via the release of cryptic variation.