Diallel Analysis of Top Size in Carrot (Daucus carota, L.) Using Biplots and Image Analysis

Crop establishment in carrot is limited by erratic germination, poor seedling growth, and delayed canopy closure. As a result, carrots compete poorly with weeds and weed control is a substantial cost of production. Varieties with rapid top growth are one option to improve weed management, but little is known about the inheritance and genetic basis of top size in carrot. This project aims to determine the genetic components contributing to top size using a diallel mating design and to develop image-based phenotyping approaches, which will facilitate future breeding efforts. Six diverse carrot inbred lines were crossed, including reciprocals, in Madison, WI in 2014 and 2015. F1 progenies and parents were grown out in a randomized complete block design (RCBD) with two blocks in El Centro, CA in 2014 and in Hancock, WI in 2015. Midseason and harvest measurements were taken for canopy height, canopy width, shoot biomass, and root biomass. Data was analyzed using Griffing’s Method I, Model I to estimate general combining ability (GCA), specific combining ability (SCA), and reciprocal effects.  Estimates are traditionally viewed in a tabular format, but graphical representation using the GGE biplot method provides opportunities to visualize heterotic groups, superior hybrid combinations, and potential gene action. Additionally, development of an image based phenotyping platform will reduce the time required for data collection. Preliminary results suggest the primary gene action for height, width, and biomass is additive. Conclusions from this analysis will provide valuable insight into the inheritance of top size traits and inform selection strategies.