Genotype x Environment Interactions for Mineral Nutrient Concentration and Yield in Organic Wheat.

Nutritional value and grain yield represent two traits vital to the interests of organic wheat farmers and consumers.  The relationship between these traits is not well understood, particularly in the context of diverse organic farming systems.  Here we report the results from a field investigation designed to shed light on the following questions: 1) whether high nutrient concentration in wheat is a trait broadly or narrowly adapted to different organic environments; and, 2) how genotype × environment (G × E) interactions play a role in determining grain yield and nutritional value in organically grown wheat.  The experiment included 18 spring wheat (Triticum aestivum L.) cultivars that were grown in three locations in 2008 and 2009 and evaluated for calcium (Ca), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), phosphorus (P) and zinc (Zn) concentrations and for grain yield.  Three replicates of each variety were grown in a randomized complete block design on three organic farms in Washington State for two years.  Significant G × E interactions were found for grain yield and all minerals except Fe.  Although there might be exceptions for individual genotypes in certain minerals, we found minimal evidence that suggests broad adaptation for mineral concentration across environments.  Significant G × Year (Y) interactions were found for grain yield and all minerals except Fe, Mn and P.   Each of the three farms had consistently high concentrations of particular minerals tested – of these, Mn showed the strongest association with soil mineral content.  Grain yield was positively correlated with Ca, Cu, Fe and P and negatively correlated with Mn, suggesting that for most minerals tested there may not be a grain yield/mineral concentration trade-off.  These results suggest that although breeding for high mineral concentration within high yielding wheat varieties should succeed, specific adaptation may limit a more comprehensive application of these varieties.