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Recurrent Selection (RS)
NDSU Products of RS (Casselton Field Day) Twenty-two recurrent selection programs are under progress at NDSU corn breeding program. Selected progenies are fed into the pedigree selection program of inbred line development. Therefore, it is essential to keep accurate records. Early generation broad-based lines that have been tested for combining ability have already demonstrated to be very competitive with popular early maturing commercial hybrids. Certain population hybrids have also demonstrated capabilities for alternative production systems. Since 2004 we have released four improved populations. Distribution of seed is in 200k lots. Most companies have requested seed of these genetically broad-based populations.
NDSU Products of RS (Casselton Field Day) Inter-population recurrent selection To date, heterotic patterns of population hybrids with relatively high high-parent heterosis values have not been exploited. We have identify potential alternative heterotic patterns for the U.S. northern Corn Belt: BS21(R)C7 x CGSS(S1-S2)C5; BS21(R)C7 x CGL(S1-S2)C5; BS21(R)C7 x NDSAB(MER-FS)C13; and BS22(R)C7 x Leaming(S)C4. The average high-parent (HP) heterosis value of population hybrids was 37.4 % (MP = 45.1 %) across 20 ND environments without inter-population improvement. Based on the data collected we decided to initiate four reciprocal full-sib recurrent selection programs. Often, predicted genetic gain is higher than observed genetic gain from recurrent selection programs. One of the reasons is the limited seed supply mating designs provide for testing reducing the repeatability of data across locations. In an effort to improve the heritability of traits, S1 progenies are produced. Then, S2 and reciprocal full-sib family seed is produced among S1 selected progenies. Since crosses are among several selected individuals per pair recurrent selection trials are grown in at least six ND locations. Intra-population recurrent selection Half-sib and S1 recurrent selection with tester (commercial) as well as full-sib recurrent selection are the main methods utilized based on the genetic architecture of the populations being improved. Typically, trials for intra-population recurrent selection run from three to five locations and all are based on lattice experimental designs. The following are latest cycles of populations being improved at NDSU:
Population Maintenance and Recombination In order to avoid expensive pollinations and to make an accurate representation of individuals per population block we cut tassels of males and females so that individuals are used only once. Typically, we harvest 100-500 ears and we make three balanced bulks of 500 seeds each. Production of Full-sib Families, Fargo, ND
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