Evaluation and selection for yield, weed suppression ability, competition traits and mineral nutrient content in organic and low-input wheat breeding systems

Organic agriculture is often criticized as low-yielding and unable to produce enough food to supply the world's population. Using wheat as a model crop species, I show that poorly adapted cultivars are partially responsible for the lower yields often found in organic farming systems when compared with conventional farming systems. This indicates that increasing yield in organic systems through breeding will require direct selection within organic systems rather than indirect selection in conventional systems.;Genetic variation for traits conducive to crop competitiveness against weeds may be concentrated in historical cultivars and landraces that were selected before the widespread use of crop protection chemicals. Regression analysis of 63 spring wheat cultivar showed an increase in yield and a decrease in weed suppression ability (WSA) over the past 150 years. Our results indicate that direct selection would be most effective for tolerance to mechanical tillage, whereas indirect selection on plant height may be effective in improving WSA. Selection of winter wheat cultivars with long coleoptiles is an important component of improving emergence, weed suppression and grain yield in low rainfall regions. Seven winter wheat cultivars were hybridized in a half-diallel and the progeny analyzed for coleoptile length in the F₁ through F₄ for response to selection, general and specific combining ability and heritability. Sustained selection over generations for coleoptile length was more effective than one generation of selection for genotypes both with and without reduced height genes.;Approximately three billion people worldwide are nutrient deficient and most of the world's poorest people are dependent on staple food crops as their primary source of micronutrients. We evaluated 63 historical and modern wheat cultivars for yield and mineral nutrient content of calcium, copper, iron, magnesium, manganese, phosphorus, selenium, and zinc. Here we report that while grain yield has increased, mineral nutrient content has decreased significantly in modern cultivars for all minerals except calcium. Plant breeders in the Pacific Northwest, through intentional selection of low ash content in soft white wheat cultivars, have contributed to the decreased mineral nutrient in modern wheat cultivars. These results contradict the theory of a genetically based, biological trade-off between yield and mineral content.