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

Abstract

Genetically diverse plant populations may be better able to exploit ecological resources and reduce interplant competition than genetically homogeneous populations. Cultivar blends can have greater productivity and yield stability than pure lines; however blend effects are not consistent. The varying levels of genetic diversity represented in blends may confound the interpretations and comparisons of the results of different blend studies. We tested the hypothesis that genetic diversity of blend components is related to blend performance by evaluating blends of a set of five early‐maturing and a set of 10 midseason‐maturing oat (Avena sativa L.) cultivars in two separate experiments at eight Iowa environments. Within each experiment, pure lines and all possible two‐way blends were evaluated for grain yield and test weight means and stability and adaptability parameters. The genetic diversity of each blend was estimated by pedigree diversity [1 − coefficient of parentage (COP)], amplified fragment length polymorphism (AFLP)‐derived genetic distances (1 − Dice coefficient), and phenotypic diversity (based on height and heading date differences). Blend response was limited in these experiments and was not correlated with any diversity measure, and blend stability parameters were not consistently related to diversity measures across experiments. We also investigated the relationship between pedigree diversity and blend performance in other crops by computing the coefficients of parentage of cultivar pairs used in previous blend studies in maize, soybean, and wheat. Pedigree diversity was correlated with higher blend response only in two of 10 experiment–environment combinations tested. Genome‐wide genetic diversity alone does not cause positive crop blend responses.