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#recurrent selection

3 public questions tagged with this topic.

Plant Breeding 3

Progeny testing is essential in recurrent selection because:

Phenotype of a single cross-pollinated plant poorly reflects its transmitting ability because heterozygosity, dominance, and micro-environment mask genotype. Superior appearance may result from favorable interlocus interactions or non-heritable environmental boost, not additive alleles that can be passed to progeny. Progeny testing evaluates half-sib or S1 families derived from selected plant in replicated trials, providing estimate of breeding value, general combining ability, and heritability. In recurrent selection, selected S1 plants are selfed and testcrossed to a common tester; progeny mean performance indicates whether parent carries concentration of favorable alleles affecting yield and adaptation. Without such testing, selection would favor non-heritable phenotypic deviates and genetic advance stalls. Progeny testing also distinguishes homozygous superior from heterozygous impostors, enabling accurate selection for low heritability traits where h² less than 0.3, which is typical for yield components requiring replicated evaluation. Combining ability terminology from Sprague and Tatum distinguishes general combining ability due to additive effects measured by progeny testing from specific combining ability due to dominance, guiding choice of testers and selection intensity in recurrent population improvement schemes worldwide.

Ref: Lush JL. Animal Breeding Plans; Acquaah Chapter 13 – importance of progeny testing in recurrent selection

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Plant Breeding 3

The objective of recurrent selection is to:

Recurrent selection functions as a population improvement strategy aimed at slowly accumulating favorable alleles at multiple loci controlling polygenic traits. Each cycle selects individuals or families with superior phenotypic value or good combining ability, then recombines them to break repulsion linkages and generate new genotypic arrays. Over cycles, frequency of positive additive alleles rises, additive genetic variance converts to breeding value, and mean performance of population for traits like grain yield, kernel weight, and stress tolerance increases. Unlike pedigree breeding which fixes alleles quickly toward homozygosity, recurrent selection maintains heterozygosity and prevents rapid drift, allowing prolonged gain across many cycles. Methods differ by selection unit: phenotypic recurrent, half-sib, full-sib, S1, and reciprocal recurrent for heterosis exploitation. Mathematically, response R = i h² σp per cycle, cumulatively shifting population mean toward desired ideotype without immediate varietal release, forming base for later line development. Allele frequency change can be modeled using quantitative genetics theory where delta p equals pqa over mean fitness; selection pushes population mean toward ideotype and recombination assembles favorable linkages while breaking repulsion phase linkages hindering yield potential improvement over long term.

Ref: Comstock RE et al. 1949 Genetics – recurrent selection theory. Hallauer Quantitative Genetics

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Plant Breeding 3

Recurrent selection is mainly practiced in:

Recurrent selection was conceptualized by Hayes and Garber for improving cross-pollinated populations where individuals are heterozygous and open-pollinated progeny expose combining ability and additive effects. In maize, brassicas, and alfalfa, gamete pool is shared through random mating, allowing allele frequencies to be altered gradually without immediate fixation. Recurrent cycles involve selection of superior individuals based on phenotype or testcross performance, intercrossing selected individuals in isolation to form new population for next cycle, increasing frequency of favorable additive alleles while maintaining variability for future gains. Self-pollinated crops are homozygous, so recurrent recombination requires manual crossing, making scheme cumbersome and less efficient. Cross-pollinated crops benefit because heterosis and inbreeding depression are managed through outcrossing, and population improvement can precede extraction of inbred lines. Thus it remains core method for open-pollinated variety and base population enrichment before inbred extraction. Reciprocal recurrent selection extends concept to improve both populations simultaneously for cross performance, exploiting overdominance and epistasis to maximize heterosis in hybrid breeding programs where combining ability and allelic complementation are critical for commercial hybrid development.

Ref: Hallauer AR & Darrah LL. Recurrent selection in maize; Sprague GF. Iowa St. J. Sci.

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