An alternative statistic for identifying lines useful for improving parents of an elite single cross

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Abstract

Theory and methods for identifying inbred lines (Iw) with favorable dominant alleles not present in an elite single cross (I1×I2) have been developed recently. Selected Iw lines can be crossed to I1 or to I2 to transfer new favorable alleles to the single cross. However, favorable alleles already present in the single cross may be lost during selection. It is important to consider both potential gain of favorable alleles from Iw and loss of favorable alleles already present in I1×I2. The "net improvement" statistic (NI)=maximum [(I1×Iw-I1x I2)/2, (I2×Iw-I1×I2)/2] estimates the number of loci where favorable alleles can be gained minus the number of loci where favorable alleles can be lost in the single cross. Because I1×I2 is constant in an experiment, the method reduces to choosing Iw lines with the best mean performance in combination with either I1 or I1. NI was compared to estimators previously proposed for identifying lines, namely: (1) minimally biased estimates (μG′) of favorable dominant alleles present in Iw but not in I1 and I2; (2) minimum estimate of an upper bound (UBND) on μG; and (3) predicted three-way cross (PTC) performance. Based on a set of maize (Zea mays L.) grain yield data, correlations among the four estimators were relatively high, but indicated that rankings of Iw lines vary with the particular estimator used. Rankings of three Iw lines based on the frequency of F2 test crosses superior to B73×Mo17 were identical to rankings based on NI, but differed from rankings based on μG′, PTC, and UBND. NI also was the best predictor of the mean of the upper 10% ({ov x}0.1) of (I2×Iw) F2×I1 or (I1×Iw) F2×I2 test crosses based on simulated data. Being a simple statistic highly correlated to {ov x}0.1, NI may be useful in applied breeding programs.

Original languageEnglish (US)
Pages (from-to)105-109
Number of pages5
JournalTheoretical and Applied Genetics
Volume80
Issue number1
DOIs
StatePublished - Jul 1 1990

Keywords

  • Favorable alleles
  • Parent selection
  • Pedigree breeding
  • Single cross
  • Zea mays L

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