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This article in CS

  1. Vol. 15 No. 4, p. 588-591
     
    Received: Jan 2, 1975


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doi:10.2135/cropsci1975.0011183X001500040041x

Gardener's Grid System and Plant Selection Efficiency in Cotton1

  1. Laval M. Verhalen,
  2. Jerry L. Baker and
  3. Ronald W. McNew2

Abstract

Abstract

Gardner's grid system was investigated relative to plant selection efficiency within an upland cotton (Gossypium hirsutum L.) cultivar known to be genetically variable for fiber length. A relatively small area, planted to ‘Westburn,’ was arbitrarily subdivided into three equalsized grids prior to harvest. One hundred individual plant selections were made in each grid on the basis of boll type and apparent yield. Then, based on fiber length, the upper and lower 10% of the plants were selected within each grid and over the area as a whole. Progeny row performances of the selected plants were obtained for fiber length in two environments. Phenotypic variances, selection differentials, selection responses, and heritabilities under the two procedures (grids vs. no grids) were then compared at the 5 and 10% levels of selection intensity. Feeding trials were conducted to test the validity of using crickets (Acheta domesticus L.) to assay the quality of forages intended for ruminant feed. Diets of forage from diverse genotypes of tall rescue (Festuca arundinacea Schreb.) produced significant differences in survival and growth rate of crickets. Certain tall rescue genotypes were consistently ranked high on the basis of cricket performance compared to others that caused almost complete mortality in all trials. Survival and growth rate were not related to in vitro digestibility; tensile strength of the leaves; and concentration in the forage of lignin, acid detergent fiber, cellulose, and ash.

In this experiment, the grid method reduced phenotypic variation by 22%; lowered selection differentials by 11 to 14%; produced 20 to 35% greater selection responses; and estimated “realized” (i.e., narrow-sense) heritabilities 41 to 52% higher than did the identical selection procedure without grids.

Based on the results of this and other experiments and on the logic underlying the method, use of grids should increase the effectiveness of plant selection regardless of crop, quantitative trait, or breeding method employed, provided there is genetic and environmental variability in the material. The method appears particularly useful when the breeder attempts to discriminate among small, inconsistent differences (i.e., when heritability is low). Use of the technique was considered for areas larger or smaller than those utilized herein, as well as for selection among progeny rows.

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