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Crop Science Abstract -

Light Intensity, Row Spacing, and Photoperiod Effects on Expression of Brachytic Stem in Soybean


This article in CS

  1. Vol. 33 No. 1, p. 29-37
    Received: Mar 19, 1992

    * Corresponding author(s):
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  1. Shurong Huang,
  2. Doyle A. Ashley  and
  3. H. Roger Boerma
  1. Dep. of Genetics



Brachytic stem trait in soybean [Glycine max (L.) Merr] is characterized by a geniculate internode arrangement and markedly shortened internodes; brachytic plants are much shorter than their nonbrachytic isolines. When the brachytic trait expression is suppressed, plants have heights similar to those of their nonbrachytic isolines. A series of greenhouse and field experiments involving light intensity and photoperiod treatments were conducted to determine their effects on plant height and other stem traits in ‘Tracy-M’ and ‘Wright’ soybean and in their brachytic near-isolines, B.Tracy-M and B-Wright. The experiments demonstrated that full expression of the brachytic stem trait is a light.regulated process. Under unshaded conditions in the field, B-Wright and B-Tracy-M had a plant height 48.7 and 78.9% of that of their respective nonbrachytic isolines. The most effective shading treatment (shade applied between 5 and 7 wk after emergence) produced a 46 and a 22% increase in plant height for B-Tracy-M and B-Wright, respectively, by increasing internode length. The shade treatment also suppressed the geniculate expression, reducing the internodal angles by 5 to 20° for B-Tracy-M and 6 to 26° for B-Wright. After shade removal, brachytic stem development resumed in subsequently formed internodes. The wide-row (76 cm) spacing (more plants per meter of row) decreased the percentage of brachytic plants at early growth stages by 47.5% and 22.7% for B-Tracy-M and B-Wright, respectively, compared with the narrow.row (25 cm) spacing. Increasing photoperiod from 14 to 16 h in the greenhouse decreased plant height and enhanced the development of brachytic stem trait. In general, B-Tracy-M appeared to be more sensitive than B-Wright to the treatments imposed in these studies.

Research supported by state and Hatch funds allocated to the Georgia Agric. Exp. Stns. and by gratns from the Georgia Agric. Commodity Commission for Soybeans.

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