Genome-Wide Genetic Diversity among Components Does Not Cause Cultivar Blend Responses

ABSTRACT vars had greater grain yield than their component pure lines on average. Furthermore, they reported that blendGenetically diverse plant populations may be better able to exploit response varied among different combinations of cul-ecological resources and reduce interplant competition than geneti-tivars.cally homogeneous populations. Cultivar blends can have greater pro-Most oat, soybean, and wheat cultivars are pure lines.ductivity and yield stability than pure lines; however blend effects are not consistent. The varying levels of genetic diversity represented in The available pure-line cultivars represent a wide range blends may confound the interpretations and comparisons of the re- of unique, homozygous genotypes often adapted to spe-sults of different blend studies. We tested the hypothesis that genetic cific environmental conditions. A genetically variable diversity of blend components is related to blend performance by plant population will often have a greater chance of evaluating blends of a set of five early-maturing and a set of 10 successful adaptation across a range of environments midseason-maturing oat (Avena sativa L.) cultivars in two separate than a genetically homogeneous population (Allard andexperiments at eight Iowa environments. Within each experiment, Bradshaw, 1964). A cultivar blend capitalizes on thispure lines and all possible two-way blends were evaluated for grain principle by using a mixture of two or more pure-lineyield and test weight means and stability and adaptability parameters. cultivars grown in the field at the same time in an at-The genetic diversity of each blend was estimated by pedigree diversit