Digging for Breakthroughs in Insect Control
DuPont scientists are continuously working to advance technology to protect crops from insects, and they are finding them in some seemingly unlikely places. That is because insecticidal substances and microorganisms that can control crop-threatening pests may be derived from a variety of environments, including soil samples. In the case of microorganisms, the challenge is to identify and develop the ones that work, out of the literally billions that may be found in as little as one gram of soil.
Along with crop protection products, insecticides that are derived from environmental sources have long been a potent weapon in the struggle against crop losses. But, like crop protection products, these natural in-plant insecticides could face reduced efficacy over time because insect populations have the ability to evolve against various control methods.
A Step Ahead
The most prominent of these products are those derived from Bacillus thuringiensis, a soil-dwelling bacterium commonly referred to as Bt. The proteins produced by Bt have been used by organic farmers for some 70 years (and for more than 20 years in genetically modified crops). Looking to expand their options, scientists at DuPont Pioneer have been aggressively searching for so-called “non-Bt” proteins — and that is where soil comes into the picture.
Not Just Any Soil
A small team of Pioneer researchers in Hayward, California began to systematically gather and analyze soil samples in search of non-Bt bacteria with genes capable of producing proteins that would be detrimental to important agricultural insect targets, including those resistant to Bt, in new ways. At first, the team began with a small number of local soil samples. The encouraging results led to new research within the organization.
As the team expanded the sampling range, they also developed new screening technology. This significantly sped up the non-Bt needle-in-a-haystack search process and helped develop new techniques for obtaining the protein concentration levels required for testing.
Persistence ultimately bore fruit. During a project review gathering at Pioneer’s Johnston, Iowa headquarters, the team took time out to collect soil samples in the site’s many test fields. As Lu Liu, Research Director at Pioneer says, “a sample from one of our own corn testing fields yielded a bacterial strain showing promising insecticidal activity.”
Through a multi-step process, the team identified the Pseudomonas chlororaphis protein responsible for the insecticidal activity. Transgenic corn plants were generated with the gene encoding this active protein and were tested under greenhouse and field conditions. The plants showed significant protection against western corn rootworm, a devastating North American and European crop pest that costs growers more than $1 billion annually. The team published their findings in a recent paper in the journal Science.
This represents a huge success, but there will be a continued need for insect control solutions for the foreseeable future. Pioneer scientists are now testing thousands of bacterial strains isolated from a large volume of soil samples each year, searching for promising insecticidal proteins that will provide new modes of action for protecting plants against insect pests.
The discovery of the non-Bt protein from P. chlororaphis is a good start. It is not only a positive step for agriculture, but also validates the hypothesis that viable alternatives to Bt can be found and potentially commercialized. Pests will continue to evolve, but thanks to the efforts of dedicated and resourceful scientists, so will the tools to combat them.