Polymorphisms in intron 1 of carrot <i>AOX2b</i> – a useful tool to develop a functional marker?

Alternative oxidase (AOX) has been proposed as a promising functional marker candidate for multiple plant stress behaviour. The present paper describes natural polymorphism in AOX2b of Daucus carota L. ( DcAOX2b ). Exon-primed intron crossing-PCR (EPIC-PCR) revealed length variation (intron length polymorphisms, ILPs) in intron 1. Six fragment patterns were identified in 40 genotypes. However, no more than two fragments were found per genotype, suggesting the presence of two alleles. The ILPs were able to discriminate between single plant genotypes in cv. Rotin and to distinguish individual wild carrot plants. The repetitive pattern of intron 1 length variation allows the grouping of genotypes for functional analysis in future studies. Sequence analysis in intron 1 of polymorphic but also of obviously identical PCR-fragments revealed underlying high levels of sequence polymorphisms between alleles and genotypes. Variation was due to repetitive insertion/deletion (InDel) events and single-nucleotide polymorphisms (SNPs). The results suggest that high AOX2b gene diversity in D. carota may be a source of functional markers for agronomic traits related to environmental stress responses.