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Title: Dissecting the genetic architecture of shoot growth in carrot (Daucus carota, L.) using a diallel mating design

item TURNER, SARAH - University Of Wisconsin
item MAURIZIO, PAUL - University Of North Carolina
item VALDAR, WILLIAM - University Of North Carolina
item YANDELL, BRIAN - University Of Wisconsin
item Simon, Philipp

Submitted to: G3, Genes/Genomes/Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2017
Publication Date: 11/19/2017
Citation: Turner, S.D., Maurizio, P.L., Valdar, W., Yandell, B.S., Simon, P.W. 2017. Dissecting the genetic architecture of shoot growth in carrot (Daucus carota, L.) using a diallel mating design. G3, Genes/Genomes/Genetics. 8(2):411-426.

Interpretive Summary: Field production of carrots is made difficult by the fact that they grow slower than most weeds early in the season. This slows down the maturation of the carrot crop and it makes weed control expensive for carrot growers, requiring the application of herbicides for conventional production, or the use of hand weeding which can cost thousands of dollars per acre for organic production. We have observed a wide range in the size of carrot tops in breeding populations and in our earlier studies we demonstrated that carrots with large tops suppress weed growth. These observations led us to this study, where we evaluated the genetic control of carrot top size. Evaluating a diverse range of inbred strains of carrots, and their hybrid combinations, we observed a large amount of genetic control of carrot top size throughout the growing season, especially near harvest time. This research suggests we can make progress in breeding carrots for larger tops that will contribute to reduced inputs and economic savings for producers. These results are of interest to carrot growers and breeders, and to plant scientists studying plant growth.

Technical Abstract: Crop establishment in carrot (Daucus carota L.) is limited by slow seedling growth and delayed canopy closure, resulting in high management costs for weed control. Varieties with improved growth habit (i.e. larger canopy and increased shoot biomass) may help mitigate weed control, but the genetics of these traits in carrot is unknown. This project used a diallel mating design coupled with Bayesian analytical methods to determine the genetic basis of carrot shoot growth. Six diverse carrot inbred lines with variable shoot size were crossed in WI in 2014. F1 hybrids, reciprocal crosses, and parental selfs were grown in a randomized complete block design (RCBD) with two blocks in CA (2014, 2015) and in WI (2015). Measurements included canopy height, canopy width, shoot biomass, and root biomass. General and specific combining abilities were estimated using Griffing’s Model I. In parallel, additive, inbreeding, epistatic, and maternal effects were estimated from a Bayesian linear mixed model, which is more robust to dealing with missing data, outliers, and theoretical constraints than traditional biometric methods. Both additive and non-additive effects significantly influenced shoot traits, with non-additive effects playing a larger role early in the growing season, when weed control is most critical. Results suggest that early season canopy growth and root size express hybrid vigor and can be improved through reciprocal recurrent selection.