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Bradyrhizobium japonicum Mutants Allowing Improved Soybean Yield in Short Season Areas with Cool Spring Soil Temperatures


This article in CS

  1. Vol. 42 No. 4, p. 1186-1190
    Received: May 29, 2001

    * Corresponding author(s): Dsmith@Macdonald.McGill.Ca
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  1. Hao Zhanga,
  2. Fredric D'Aousta,
  3. Trevor C. Charlesb,
  4. Brian T. Driscolla,
  5. B. Prithiviraja and
  6. Donald L. Smith *a
  1. a Dep. of Natural Resource Science, Macdonald Campus of McGill Univ., 21111 Lakeshore Road, Ste-Anne-de-Bellevue, QC, Canada H9X 3V9
    b Dep. of Biology, Univ. of Waterloo, Waterloo, ON, Canada N2L 3G1


In short-season production areas, cool soil temperature is a major factor potentially limiting soybean [Glycine max (L.) Merr.] plant growth and yield. Genistein (4′,5,7-trihydroxyisoflavone) is a signal compound secreted from soybean roots and is essential to establishment of the soybean–Bradyrhizobium japonicum N-fixing symbiosis. The addition of genistein to soybean inocula has proven to be an effective means of generating increases in N fixation and yield; however, genistein is costly. We used ultraviolet (UV) mutagenesis to make 10 mutants of USDA 110 that express the nod genes without exposure to genistein. A field experiment was conducted at the Lods Agronomy Research Centre in southwestern Quebec in 1998 and 1999. The treatments consisted of factorial combinations of inoculant type [no inoculant (control) and inoculants containing the mutants or the wildtypes 532 C or USDA 110] and soybean cultivar (OAC Bayfield and Maple Glen). Inoculation with mutant strains Bj 30055 and Bj 30058 resulted in greater soybean yields than inoculation with 532 C (6.2% increase, averaged across the 2 yr) or the wildtype USDA 110 (9.9% increase, averaged across the 2 yr). These increases were largely due to increases in pod and seed number. These results showed that mutants that express nod genes in the absence of plant-to-bacteria signal compounds can help to overcome the low temperature limitation of soybean nodulation leading to improved growth and yield of soybean crops grown in areas with cool spring soils.

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Copyright © 2002. Crop Science Society of AmericaPublished in Crop Sci.42:1186–1190.