Mining for candidate genes controlling secondary growth of the carrot storage root

Authors: MACKO-PODGÓRNI, ALICJA - Agricultural University Of Poland; STELMACH, KATARZYNA - Agricultural University Of Poland; KWOLEK, KORNELIA - Agricultural University Of Poland; MACHAJ, GABRIELA - Agricultural University Of Poland; ELLISON, SHELBY - University Of Wisconsin; Senalik, Douglas; Simon, Philipp; GRZEBELUS, DARIUSZ - Agricultural University Of Poland

Submitted to: International Journal of Molecular Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2020
Publication Date: 6/15/2020
Citation: Macko-Podgórni, A., Stelmach, K., Kwolek, K., Machaj, G., Ellison, S., Senalik, D.A., Simon, P.W., Grzebelus, D. 2020. Mining for candidate genes controlling secondary growth of the carrot storage root. International Journal of Molecular Sciences. 21(12). Article 4263. https://doi.org/10.3390/ijms21124263.
DOI: https://doi.org/10.3390/ijms21124263

Interpretive Summary: For the last 500 years, the shape of carrot roots has been the major characteristic used to determine the use of carrots by industry and by consumers with thick, shorter carrots used for canning and freezing, and thinner, usually longer carrots used for fresh market sale as whole carrots and "baby"/ "cut and peeled" carrots. While important for determining the use of carrots, the genetic control of storage root shape has not been well-described by researchers. In this study the genetic make-up of 307 carrots that varied widely in shape from very long and thin to short golf-ball-shaped storage roots. In a genetic analysis of these carrots a cluster of genes on one chromosome was found to account for a significant amount of the genetic variation in carrot root diameter. This study is of interest to carrot growers, vegetable breeders, seed companies, and plant biologists studying plant growth and development.

Technical Abstract: Diverse groups of carrot cultivars have been developed to meet consumer demands and industry needs. Varietal groups of the cultivated carrot are defined based on the shape of roots. However, little is known about the genetic basis of root shape determination. Here, we used 307 carrot plants from 103 open-pollinated cultivars for a genome wide association study to identify genomic regions associated with the storage root morphology. We found that a 180 kb-long region on carrot chromosome 1 explained 10% of the total observed phenotypic variance in the shoulder diameter. Within that region, DcDCAF1 and DcBTAF1 genes were proposed as candidates controlling secondary growth of the carrot storage root. Their expression profiles differed between the cultivated and the wild carrots, likely indicating that their elevated expression was required for the development of edible roots. They also showed higher expression at the secondary root growth stage in cultivars producing thick roots, as compared to those developing thin roots. This study provided evidence for a likely involvement of DcDCAF1 and/or DcBTAF1 in the development of the carrot storage root and developed a genotyping assay facilitating the identification of variants in the region on carrot chromosome 1 associated with secondary growth of the carrot root.