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A group of transgenic barley plants expressing the bar selectable marker gene did not produce viable offspring.

Manipulated Organism: Barley (Hordeum vulgare).

Inserted Transgenes: bar gene from Streptomyces hygroscopicus, which produces the enzyme PAT. The PAT enzyme inactivates the herbicide phosphinothricin, also known as glufosinate. bar gene expression was controlled by the maize ubiquitin promoter.

Goal of This Study: As part of an effort to map genes in barley, twenty transgenic Golden Promise barley lines containing the bar gene in unique locations (GP-bar) were crossed with Oregon Wolfe Barley Dominant (OWBD) stock.

Results of This Study:
  • Even though none of the transgenic Golden Promise lines exhibited morphological abnormalities, only 4 of the 20 OWBD x GP-bar crosses produced viable seed. Progeny from the other 4 crosses showed moderate to severe reductions in growth rate, turned yellow, and eventually died before setting seed.

  • Further crosses showed that GP-bar lines with low levels of the enzyme PAT could produce viable offspring with OWBD lines.

  • Genetic mapping identified a single locus on the long arm of barley chromosome 6 as responsible for the sensitivity of the OWBD population to high levels of PAT expression.

Additional Comments: The researchers comment that their results may serve to "remind us of the complex and sometimes surprising aspects of higher plant genomes" (p. 386).

Source: Bregitzer, P., L. D. Cooper, P. M. Hayes, P. G. Lemaux et al. (2007). "Viability and bar Expression are Negatively Correlated in Oregon Wolfe Barley Dominant Hybrids," Plant Biotechnology Journal vol. 5, pp. 381-8.

Author Affiliations: USDA Agricultural Research Service, Abderdeen, Idaho; Oregon State University; University of California, Berkeley.

Funding: USDA Agricultural Research Service; National Science Foundation.

Product Status: Not on the market as of 2009.

Copyright 2009 The Nature Institute.

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