REPRODUCTION BY ROOT-KNOT AND RENIFORM NEMATODES ON TRANSGENIC COTTON CULTIVARS GROWN COMMERCIALLY IN 1998

Authors: Robinson, Arin; Bridges, Alan

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 2/16/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Nematodes are microscopic worms that live in the soil. They can be devastating to certain crops because of damage they cause while feeding on roots. In cotton, nematodes are considered a major root disease problem. In 1998, almost half of the U.S. cotton acreage was planted to transgenic cultivars, that is cotton cultivars whose chromosomes had been modified by genetic engineers by inserting one or more artificial genes called transgenes. These transgenes protect cotton plants from insects and herbicides and are known commonly as Bt, BXN, and Roundup Ready. It would be very helpful to farmers to know whether or not the transgenes influence the ability of nematodes to feed and reproduce on cotton roots, and so we evaluated reproduction by the two most important nematode pests of cotton on the 15 most widely grown transgenic cultivars. Appropriate non- transgenic cultivars were included in the study for comparison. We found that even though some transgenes greatly affect insect populations, none had any effect on nematodes. We did see some big differences among cultivars in nematode reproduction, but these differences were not related to the genetic changes made by genetic engineers.

Technical Abstract: Twenty-one transgenic genotypes of Upland cotton, including the 15 most widely planted transgenic cultivars in 1998 and their nontransgenic parents, were evaluated under growth chamber conditions for resistance to the nematodes Meloidogyne incognita (root-knot nematode) and R. reniformis. The highly M. incognita-resistant breeding line Auburn 623 RNR, the M. incognita-resistant cultivar Stoneville LA887, and the susceptible obsolet cultivar Deltapine 16 were included as controls. No important decrease in nematode reproduction was attributable to any transgene in any cultivar. Some other differences in nematode reproduction, however, were apparent. R. reniformis reproduction was prolific on all cultivars and on eight significantly exceeded Deltapine 16. In contrast, 10 cultivars exhibited M. incognita gall ratings and/or egg densities on roots significantly lower than on Deltapine 16. Six Stoneville breeding lines (experimental transgenics) had levels of M. incognita root galling and reproduction comparable to Stoneville LA887.