Abstract
BackgroundTo study the potential of genomic selection for heterosis resulting from multiplicative interactions between additive and antagonistic components, we focused on oil palm, where bunch production is the product of bunch weight and bunch number. We simulated two realistic breeding populations and compared current reciprocal recurrent selection (RRS) with reciprocal recurrent genomic selection (RRGS) over four generations. All breeding strategies aimed at selecting the best individuals in parental populations to increase bunch production in hybrids. For RRGS, we obtained the parental genomic estimated breeding values using GBLUP with hybrid phenotypes as data records and population specific allele models. We studied the effects of four RRGS parameters on selection response and genetic parameters: (1) the molecular data used to calibrate the GS model: in RRGS_PAR, we used parental genotypes and in RRGS_HYB we also used hybrid genotypes; (2) frequency of progeny tests (model calibration); (3) number of candidates and (4) number of genotyped hybrids in RRGS_HYB.ResultsWe concluded that RRGS could increase the annual selection response compared to RRS by decreasing the generation interval and by increasing the selection intensity. With 1700 genotyped hybrids, calibration every four generations and 300 candidates per generation and population, selection response of RRGS_HYB was 71.8 % higher than RRS. RRGS_PAR with calibration every two generations and 300 candidates was a relevant alternative, as a good compromise between the annual response, risk around the expected response, increased inbreeding and cost. RRGS required inbreeding management because of a higher annual increase in inbreeding than RRS.ConclusionsRRGS appeared as a valuable method to achieve a long-term increase in the performance for a trait showing heterosis due to the multiplicative interaction between additive and negatively correlated components, such as oil palm bunch production.
Highlights
To study the potential of genomic selection for heterosis resulting from multiplicative interactions between additive and antagonistic components, we focused on oil palm, where bunch production is the product of bunch weight and bunch number
As the Quantitative trait loci (QTL) number and percentage of pleiotropic QTL are unknown, we considered a range of values for these two parameters, assuming that this would include the true value of number of QTL (nQTL) and pQTL
Number of genotyped hybrids in RRGS_HYB In order to simplify the interpretation of the results, we first focused on the number of genotyped hybrid individuals, as it had a major effect on the annual selection response in RRGS_HYB
Summary
To study the potential of genomic selection for heterosis resulting from multiplicative interactions between additive and antagonistic components, we focused on oil palm, where bunch production is the product of bunch weight and bunch number. Heterosis in a complex trait can result from the multiplicative interaction between additive and negatively correlated components ([7, 8] p68-71]) This can be the case for yield in crops as a product of fruit weight and number, or plant height as a product of internode number and length. As GS proved to be efficient for single additive traits in many studies, it could be beneficial in the case of multiplicative interactions between complementary parental components This potential benefit over conventional phenotypic selection has not been quantified so far. This results in heterosis in the hybrids for bunch production, which is at least 25 % higher than in the parental populations [11]
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