Nine diseases that threaten food and how GM can help
Nature is in constant war with agriculture, with insects, weeds and disease as its primary weapons. Advances in genetic modification offer some unique tools that can help increase food production despite these challenges.
Most of the “GMO Crops” that have been commercialized are either insect resistant or herbicide tolerant. Biotechnology can also be used to generate crops that are resistant to plant diseases. So far, there are only two examples of disease resistance available to farmers: the papayas resistant to ringspot virus and squash resistant to zucchini yellow mosaic and watermelon mosaic viruses. That narrow offering is not for a lack of need or technical potential. In fact, biotech approaches could uniquely address some of the most significant disease issues in global agriculture. The limitation mainly reflects the success of the anti-GMO movement in creating controversy. This has induced brand-sensitive food system players to use their leverage to prevent the development or introduction of “GMO” disease resistant versions of crops where they would make the most sense.
If we let ourselves imagine what could be, there are three important categories of plant disease of particular interest for the use of genetic engineering:
- Systemic diseases spread by insect vectors
- Diseases of crops for which conventional breeding is far too slow and/or disruptive to key quality attributes
- Crop diseases which are not amenable to safe and effective chemical control
Systemic diseases spread by insect vectors
Fungi cause most plant diseases, but plants can also be infected by viruses and bacteria. In most of these cases, specific insects spread pathogens from plant to plant in much the same way that the Aedes aegypti mosquito spreads a human disease like Yellow Fever. For plants, the vector insects are the ones that use specialized mouthparts to penetrate plant cells to suck out nutrients – things like aphids, thrips, mealy bugs and psyllids. The viruses or bacteria have specific associations that allow them to be picked up from an infected plant on the mouthparts of the “bug” and then released inside of the next plant. Those infections can severely damage the plant and even kill it.
In many cases, the only way such diseases can be controlled is to use insecticides to kill the vectors. Often it requires nearly complete insect control to adequately protect the crop. That means intensive insecticide use in some cases, but in other cases it isn’t feasible to stop the spread of the disease. That was the case with papaya ringspot virus which was seriously compromising production Hawaii in the early 1990s–the farmers were fighting a losing battle to save their plantings. The introduction of transgenic virus resistance in 1998 saved the papaya industry.
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