Analysis of Genetic and Environmental Effects on Broccoli Cultigens Grown in Diverse Environments in the Eastern United States

Glucosinolates (GS) are secondary metabolites in broccoli that break down into isothiocyanates (ITCs) with important anti-carcinogenic effects in human nutrition.  As part of a USDA SCRI sponsored research project to improve the consistency and profitability of broccoli production in the eastern US, we evaluated GS content of broccoli cultigens grown in diverse environments. Three replications of six cultigens were grown in five locations (MA, NY, VA, NC and SC) at two different production times.  Floret tissue was analyzed for GS content by HPLC and quantified by authenticated standards.  The genetic by environment (GxE) interactions evaluated in similar experiments are often analyzed by evaluating averages across replications for a genotype in different environments and then analyzing the means.  Analysis of data from this experiment using SAS Mixed Model Procedures revealed that cultigen, location, season and their interactions significantly affected GS content.  One of our goals was to determine which cultigens had a consistently high GS content across the widest range of environments.  Additive Main Effects and Multiplicative Interaction (AMMI) models were used to combine the analysis of variance for additive main effects with principal component analysis for non-additive residuals. Genetic by environment interactions indicate whether a cultigen can be used over a diverse range of environmental conditions or whether separate cultigens must be developed for different environments.  The data presented here compare the adaptability of six commercial cultigens across environments in the eastern US. Two of the six cultigens maintain high GS contents across five of the location/production time combinations.  The other four cultigens had GS contents below the experiment overall mean in the same five location/production time combinations. Five of the location/production time combinations had lower GS content than the experimental overall mean for all cultigens.  The influence of the specific environments evaluated on the GS content of the cultigens in the experiment will be discussed.  Based on the results from this experiment, we plan to use a similar approach to evaluate the GxE interactions that impact GS content of new breeding lines and use that information in breeding efforts to improve future broccoli cultigens.