Insect-resistant, transgenic cotton was more susceptible to fungal disease
than its parent line.
Manipulated Organism:
(Gossypium hirsutum).
Inserted Transgenes:
cry1A gene derived from Bacillus thuringiensis
(Bt) and the CpTI gene from cowpeas, which produces a trypsin inhibitor.
These proteins are toxic to various insect pests.
Goal of This Study:
Motivated by reports from several Chinese provinces that GM
insect-resistant cotton varieties had reduced disease resistance, the
authors investigated the resistance of GM varieties and their respective
non-GM parental lines to the soil fungus Fusarium oxysporum.
Results of This Study:
-
The GM cultivar Zhong-41 was derived from the cultivar Zhong-23, which
is known for its resistance to F. oxysporum. However, Zhong-41
showed significantly more injury (wilted, yellow leaves) than Zhong-23
when exposed to F. oxysporum, with a disease index rating of 76
versus 42 (Z-41 versus Z-23).
-
Whereas the germination rate of F. oxysporum spores in the
presence of root exudate from Zhong-41 (GM) was 79%, with root exudate
from Zhong-23 (non-GM parent) the fungal spore germination rate was
only 48%.
-
Chemical analysis revealed significant differences in the composition
of root exudates from Zhong-41 and Zhong-23. The more susceptible
GM cultivar Zhong-41 produced exudate with elevated levels of several
amino acids. Additionally, whereas glucose was the only sugar detected
in exudate from Zhong-23, in Zhong-41 exudate the authors detected large
quantities of fructose and maltose, which can support fungal growth.
Source:
Li, X., B. Liu, S. Heia, D. Liu et al. (2009). "The Effect of Root
Exudates from Two Transgenic Insect-Resistant Cotton Lines on the Growth
of Fusarium oxysporum," Transgenic Research vol. 18,
pp. 757-67.
Author Affiliations:
Nanjing Forestry University, China; Ministry of Environmental Protection
of China; Genok Center for Biosafety, Norway; Chinese Academy of
Agricultural Sciences.
Funding:
Jiangsu Science Foundation; China's National Special Transgenic Project.
Product Status:
Transgenic cotton containing the cry1A and CpTI genes
has been developed by the Chinese Academy of Agricultural Sciences and is
widely grown in China.
Copyright 2009 The Nature
Institute.
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