Accuracy of Selection in Early Generations of Field Pea Breeding Increases by Exploiting the Information Contained in Correlated Traits

Accuracy of predicted breeding values (PBV) for low heritability traits may be increased in early generations by exploiting the information available in correlated traits. We compared the accuracy of PBV for 10 correlated traits with low to medium narrow-sense heritability (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>h</mi><mn>2</mn></msup><mo stretchy="false">)</mo></mrow></semantics></math></inline-formula> in a genetically diverse field pea (<i>Pisum sativum</i> L.) population after univariate or multivariate linear mixed model (MLMM) analysis with pedigree information. In the contra-season, we crossed and selfed S₁ parent plants, and in the main season we evaluated spaced plants of S₀ cross progeny and S₂₊ (S₂ or higher) self progeny of parent plants for the 10 traits. Stem strength traits included stem buckling (SB) (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>h</mi><mn>2</mn></msup></mrow></semantics></math></inline-formula> = 0.05), compressed stem thickness (CST) (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>h</mi><mn>2</mn></msup></mrow></semantics></math></inline-formula> = 0.12), internode length (IL) (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>h</mi><mn>2</mn></msup></mrow></semantics></math></inline-formula> = 0.61) and angle of the main stem above horizontal at first flower (EAngle) (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>h</mi><mn>2</mn></msup></mrow></semantics></math></inline-formula> = 0.46). Significant genetic correlations of the additive effects occurred between SB and CST (0.61), IL and EAngle (−0.90) and IL and CST (−0.36). The average accuracy of PBVs in S₀ progeny increased from 0.799 to 0.841 and in S₂₊ progeny increased from 0.835 to 0.875 in univariate vs MLMM, respectively. An optimized mating design was constructed with optimal contribution selection based on an index of PBV for the 10 traits, and predicted genetic gain in the next cycle ranged from 1.4% (SB), 5.0% (CST), 10.5% (EAngle) and −10.5% (IL), with low achieved parental coancestry of 0.12. MLMM improved the potential genetic gain in annual cycles of early generation selection in field pea by increasing the accuracy of PBV.