Herbicide Resistance Gene In Black-Grass and Rye-Grass Identified

Black-grass (Alopecurus myosuroides), a serious weed of arable fields that is widley resistant to herbicides © Bas Kers, via Flickr (CC-BY-NC-SA 2.0)
Black-grass (Alopecurus myosuroides), a serious weed of arable fields that is widley resistant to herbicides © Bas Kers, via Flickr (CC-BY-NC-SA 2.0)

BBSRC (Biotechnology and Biological Sciences Research Council) and Syngenta funded scientists at the University of York and University of Durham have discovered a gene called AmGSTF1 that plays a key role in controlling multiple herbicide resistance in black-grass (Alopecurus myosuroides) and annual rye-grass (Lolium rigidum). Now the gene that confers resistance has been identified, it is hoped that chemicals that inhibit the gene may be able to be used in future to make herbicides effective against resistant weeds.

Black-grass and rye-grass are widespread weeds which cause problems in cereal and oilseed rape farming. Management using herbicides is becoming increasingly difficult since both black-grass and rye-grass can acquire a single defence mechanism that confers resistance to multiple herbicides- known as multiple herbicide resistance. The genetics of multiple herbicide resistance have been poorly understood until recently, however scientists have now discovered that a gene producing an enzyme called glutathione transferase (GST) is responsible for multiple herbicide resistance. Scientists created transgenic thale cress (Arabidopsis thaliana) plants with the GST producing gene inserted which were resistant. GSTs are known to detoxify herbicides, but project leader Professor Rob Edwards of the Centre for Novel Agricultural Products at the University of York believes that the gene they discovered works as a kind of ‘master switch’ that activates a range of protective mechanisms in the plant. When resistant plants with the GST gene are sprayed with GST inhibiting chemicals, they become susceptible to herbicides. This demonstrates the potential for using GST inhibiting compounds in future herbicide formulations to manage resistant rye-grass and black-grass. These weeds are currently very difficult to manage due to their widespread herbicide resistance.

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New Mapping Tool Tracks Insecticide Resistance In Malaria Carrying Mosquitoes

A mosquito in the genus Anopheles, which can transmit human malaria. Image by Yasser via Flickr (CC-BY-2.0)
A mosquito in the genus Anopheles, which can transmit human malaria. Image by Yasser via Flickr (CC-BY-2.0)

Progress in malaria control in the past decade can be attributed largely to a massive increase in the number of insecticide based management programmes targeting malaria carrying mosquitoes, using methods that include indoor residual spraying and insecticide impregnated bed nets. The effectiveness of these management techniques is now being compromised by insecticide resistant mosquito populations. In 2012, the UN World Health Organisation (WHO) launched a strategic plan to help fight insecticide resistance in malaria vectors. A crucial part in the management of insecticide resistant mosquito populations is access to current information on insecticide resistant populations.  IR Mapper is a new interactive online mapping tool used to track insecticide resistance in mosquitoes. The tool collaborates reports of insecticide resistance in malaria vector mosquitoes into maps which aim to assist vector control strategies. Data consolidation for the programme was conducted by Swiss company Vestergaard Frandsen, the Kenyan Medical Research Institute (KEMRI) and the US Centers for Disease Control and Prevention (CDC).   To make this information available to users, an interactive map of all publicly available insecticide resistance data has been developed, with an interface developed by ESRI Eastern Africa

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Plantwise Photo Of The Month – July

A photograph taken at the Plantwise stand at the 18th CABI Review Conference which took place in Oxford from the 27-28th June. Director of the Plantwise Knowledge Bank, Shaun Hobbs, is pictured to the left addressing delegates at the stand. Image © CABI
A photograph taken at the Knowledge Bank stand at the 18th CABI Review Conference which took place in Oxford from the 27-28th June. Director of the Plantwise Knowledge Bank, Shaun Hobbs, is pictured to the left addressing delegates at the stand. Image © CABI

This photo shows the Plantwise Knowledge Bank booth at the CABI Review Conference 2013, which took place from the 27-28th June in Oxford, UK. 70 delegates from 36 countries attended the review conference, in which research priorities aimed at protecting global food supply were discussed.

To find out more about the review conference you can watch this video

The Evolution of Insect Resistance to Bt Crops

A group of scientists at the University of Arizona have this week published a paper in Nature Biotechnology on the evolution of resistance in insect pests populations to insecticidal proteins from Bacillus thuringiensis (Bt) that are produced by transgenic crops. Resistance is defined as the phenotype of an individual that gives the individual the ability to survive on a transgenic insecticidal plant from egg to adult and provide viable offspring. The team analysed field and laboratory data from seventy-seven studies of thirteen pest species in eighteen countries across five continents. Entomologist Bruce Tabashnik and colleagues found well documented cases of field-evolved resistance to Bt crops in five major pests as of 2010. 60% of these cases occurred in the U.S.A, where approximately half of the world’s Bt crop acreage is planted. In some cases, resistance to Bt evolved within as little as two to three years, whilst in other cases Bt crops have remained effective for more than 15 years. The research team aimed to better understand how quickly insect populations are evolving resistance to Bt crops and how this is occurring.

Workshop participants assess a range of fodder and cereal crops that can be used as “refugia”, fostering stem borers susceptible to the Bt toxin. In a longstanding partnership under the Insect Resistant Maize for Africa (IRMA) project , CIMMYT works with the Kenya Agricultural Research Institute (KARI) to offer farmers maize varieties that resist borers, which otherwise cause heavy losses (approximately 12% of Kenya’s annual maize crop). In addition to conventional breeding, one source of resistance in developing these varieties has been the soil bacterium Bacillus thuringiensis. A gene from this bacterium inserted into “Bt maize” causes it to produce a protein that is selectively toxic to certain borer species. However, mutant resistant borers unaffected by the toxin will flourish and eventually predominate, unless farmers use refugia to maintain a susceptible population. At this workshop in December 2005, sponsored by IRMA at KARI’s Kitale center, 50 participants—including researchers, extension workers, and farmers—learned about progress in the development of insect-resistant maize and the importance of refugia, evaluating numerous crops in the field for their potential as refugia. For more information, see CIMMYT's December 2005 e-news story "Bug Havens Keep Maize Pest-Proof," available online at: http://www.cimmyt.org/newsletter/86-2005/344-bug-havens-keep-maize-pest-proof.  Image © CIMMYT (CC-BY-NC-SA 2.0)
Women assess a range of fodder and cereal crops that can be used as “refugia for stem borers susceptible to the Bt toxin. In a longstanding partnership under the Insect Resistant Maize for Africa (IRMA) project , CIMMYT works with the Kenya Agricultural Research Institute (KARI) to offer farmers maize varieties that resist borers, which otherwise cause heavy losses (approximately 12% of Kenya’s annual maize crop). In addition to conventional breeding, one source of resistance in developing these varieties has been the soil bacterium Bacillus thuringiensis. A gene from this bacterium inserted into “Bt maize” causes it to produce a protein that is selectively toxic to certain borer species. However, resistant borers unaffected by the toxin will reproduce and eventually predominate, unless farmers use refugia to maintain a susceptible population. 
Image © CIMMYT (CC-BY-NC-SA 2.0)

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Plantwise Photo Of The Month – June

Plant clinic in Machakos, Kenya
Plant clinic in Machakos, Kenya © CABI

Photo Of The Month for June shows a plant clinic during market day at a village near Machakos, 50 kilometers outside Kenya’s capital city Nairobi. The photo shows a farmer showing a crop sample to a plant doctor, who is using his knowledge and reference material on the table to diagnose what is wrong with the crop and provide management information to the farmer.  You can read more about plant clinics in Kenya here

Glucose Leaves A Bitter Taste As Cockroaches Learn to Avoid Insecticide Baits

Populations of the German cockroach (Blattella germanica) have rapidly evolved to be repelled by the glucose in insecticide baits that are used to kill them. Scientists found that the cockroaches had a ‘re-organised’ sense of taste which makes them perceive the glucose in the insecticide bait as bitter and repellent rather than sweet. Researchers first noticed that some pest controllers were failing to control cockroaches using insecticide baits mixed with glucose because the insects were avoiding the baits. It was discovered that within a matter of years certain cockroach populations had developed a new behavioural trait known as glucose aversion. A paper published in the journal Science describes the mechanism behind this avoidance.

Blattella germanica, the German cockroach. Populations of this cockroach have evolved an aversion to glucose, which mean they are repelled by insecticide baits containing glucose and avoid them © Luis Miguel Bugallo Sánchez via Wikimedia Commons (CC-BY-SA 3.0, 2.5, 2.0, 1.0)

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Black Rot Disease Hits Uganda

A photograph of a cabbage leaf showing symptoms of black rot. Image by USDA Forest Service via Wikimedia Commons (CC-BY 3.0)
A photograph of a cabbage leaf showing symptoms of black rot. Image by USDA Forest Service via Wikimedia Commons (CC-BY 3.0)

Vegetable farmers in the Kayunga and Mukono districts of Uganda are reporting crop losses due to black rot disease. One farmer, Twaha Kahooza of Kyampisi village, Kayunga Sub-county, says he had planted four acres of cabbages and was expecting about Shs18m (about £4,500 or US$7,000) from the harvest, however he only managed to get Shs5m (about £1,200 or US$2,000).

Black rot is caused by the bacterium Xanthomonas campestris pv. campestris and is one of the most destructive diseases of cabbage and other crucifers such as  broccoli, brussels sprouts, Chinese cabbage, collards, kohlrabi and mustard. The disease is usually most prevalent in low lying areas where plants remain wet for long periods. The disease is characterized by a yellow V-shaped lesion at the leaf margin which turns brown as the leaf area expands. The disease can also affect seedlings and can enter the plant through insect feeding or injury to the plant. Management of black rot in crucifers includes obtaining certified, pathogen free seed, ensuring there is enough space between plants and crop rotation.To read more about black rot and black rot management visit factsheets on the Plantwise Knowledge Bank.  

To read a Plantwise Factsheet for Farmers written in Uganda click here. 

To find out more about Plantwise plant clinics running in Uganda, click here

References:

‘Farmers count losses over black rot disease in cabbage’, Fred Muzaale, April 2013, Daily Monitor