Insect-resistant, transgenic cotton was more susceptible to fungal disease
than its parent line.
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
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.
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,
Nanjing Forestry University, China; Ministry of Environmental Protection
of China; Genok Center for Biosafety, Norway; Chinese Academy of
Jiangsu Science Foundation; China's National Special Transgenic Project.
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