|Helland, Sara - IOWA STATE UNIVERSITY|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 27, 2003
Publication Date: September 1, 2003
Citation: HELLAND, S.J., HOLLAND, J.B. GENOME-WIDE GENETIC DIVERSITY AMONG COMPONENTS DOES NOT CAUSE CULTIVAR BLEND RESPONSES. CROP SCIENCE. Interpretive Summary: Across varying environmental conditions, genetically diverse plant populations may be at an advantage compared to genetically homogeneous populations. Cultivar blends (representing more genetically diverse populations) often have greater productivity and yield stability than pure-lines (representing the more common type of cultivar that lacks genetic diversity), however blend effects are not consistent. Different cultivar blends represent different levels of genetic diversity. 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 effects by evaluating blends of a set of five early-maturing and a set of ten midseason-maturing oat (Avena sativa L.) cultivars in two separate experiments at eight Iowa environments. We estimated genetic diversity using pedigree methods, DNA markers, and phenotypic variation. Blend response was not consistently related to any of these measures of genetic diversity. We suggest that diversity at specific genes affecting competitive ability of plants is more important than diversity at all genes for predicting blend response. Future research should be aimed at identifying those genes that are important for blend response.
Technical Abstract: Genetically diverse plant populations may be better able to exploit ecological resources and reduce inter-plant competition than genetically homogeneous populations. We tested the hypothesis that genetic diversity of blend components is related to blend effects by evaluating blends of a set of five early-maturing and a set of ten 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), AFLP-derived genetic distances (1 - Dice coefficient), and phenotypic diversity (based on height and heading date differences). Blend response was not correlated with any diversity measure. Greater phenotypic diversity in height and greater pedigree diversity were related to greater test weight adaptability of blends in the midseason-maturity experiment (r2=0.21, P=0.001 and r2=0.32, P=0.0001, respectively). In contrast, lower yield adaptability of blends was associated with greater pedigree diversity and greater genetic diversity in this experiment (r2=0.12, P=0.02, and r2=0.19, P=0.003). We also investigated the relationship between pedigree diversity and blend performance in other crop species by computing the coefficients of parentage of cultivar pairs used in previous blend studies in maize, soybean, and wheat. Greater pedigree diversity was correlated with higher blend response only in the soybean experiment (r2=0.18, P=0.05).