Archive for the ‘Host plant resistance’ Category
Researchers studied the genetic components of cultivated and wild cassava
They unravelled cassava genome that could aid creation of good varieties
But an expert says the findings should not be linked to better traits of cassava
Researchers have sequenced the genome of the cassava — enabling them to better understand the genetic basis the plant’s disease resistance, quality and crop maturity.
A research team in Kenya spent four years decoding the DNA, the genetic material, of the cassava plant, which is widely farmed and eaten across the tropics.
“Cassava is the main food security crop of [Africa], so providing a high yield in poor soils with minimal water can be crucial when other crops fail.”
The researchers identified the order of the genetic letters of 53 cultivated and wild cassava plant materials from Africa, Asia, South America and Oceania — a process called genome sequencing. They also sequenced five cassava-related plants such as M. glaziovii and identified the genetic components of 268 African cassava varieties.
The study which started in 2012, was aimed at increasing the genomic resources for cassava, says Morag Ferguson, a co-author of the study and a molecular geneticist at the International Institute of Tropical Agriculture (IITA), Kenya. The research was published in the journal Nature Biotechnology last month.
“The study includes 97 per cent of the estimated genes,” Ferguson tells SciDev.Net. “The large amount of DNA sequence information provides insights into the origin of cassava and resources for the improvement of cassava”.
For example, the genome holds information on resistances to cassava brown streak disease, a devastating viral disease affecting cassava in southern, eastern and central Africa.
Sequence information, according to Ferguson, revealed that some disease-resistant cassava varieties in Tanzania, including Namikonga and Muzege, contain sections of genomes of M. glaziovii.
“Cassava is the main food security crop of [Africa]”, so providing a high yield in poor soils with minimal water can be crucial when other crops fail, says Ferguson.
The study was conducted by researchers from countries as varied as Fiji, Kenya, Micronesia, Nigeria, Tanzania and United States.
Paul Kimani, a plant breeder from Kenya’s University of Nairobi says the main contribution of the findings is a clear demonstration of the genetic relationships among the various species, including cultivated cassava, its wild relatives and others in the secondary or even tertiary gene pool.
“What it does not do is link the genes with any economically important traits such as disease resistance, nutritional quality or agronomic traits,” he says.
Kimani explains that because cassava breeders often have little genetic variety among their crop, an epidemic can easily cause severe damage, leading to rapid spread of diseases such as cassava mosaic disease and brown streak disease in Africa.
“The key issue is whether the wild cassava has genes for economically important traits such as resistance to diseases, which can be transferred to commercial varieties,” Kimani tells SciDev.Net.
This piece was produced by SciDev.Net’s Sub-Saharan Africa English desk.
Jessen V. Bredeson and others Sequencing wild and cultivated cassava and related species reveals extensive interspecific hybridization and genetic diversity (Nature Biotechnolgy, 18 April 2016)
– See more at: http://www.scidev.net/global/biotechnology/news/cassava-genome-mapped-boost-qualities-2.html?utm_medium=email&utm_source=SciDevNewsletter&utm_campaign=international%20SciDev.Net%20update%3A%209%20May%202016#sthash.co9ylka7.dpuf
Scientists in Japan have found a way to create high-yielding rice with long-lasting resistance to the devastating rice blast fungus.
Sufficient rice to feed 60 million people is destroyed by the blast fungus, Magnaporthe grisea — also known as Magnaporthe oryzae — every year.
Some rice is naturally resistant but is often also of lower yield. Now a team led by Shuichi Fukuoka from the National Institute of Agrobiological Sciences in Japan has engineered good quality rice that is both resistant to blast disease and high-yielding.
Their research was published in Science last week (21 August).
By comparing japonica rice that is resistant to blast disease with rice that succumbs to infection, Fukuoka found that a change in a key gene called Pi21 can mean the difference between devastating infection and mild disease.
Fukuoka says even plants with the resistant form of the gene become infected, but “The damage they suffer is not so serious, making it possible to reduce the amount of fungicide used by 50 per cent.”
He says his team’s findings will be particularly useful in mountainous areas where blast disease is a serious threat.
There have been many previous attempts to engineer resistant rice strains by making specific adjustments to plant immunity to allow the plants to recognise and resist the fungus.
But according to Nick Talbot, professor of molecular genetics at Exeter University in the UK, many of these modifications have a field life of just 2–3 years, as the fungus is quick to find ways to circumvent them and avoid being recognised.
Having the resistant form of Pi21, however, means a plant increases its defences against infection in general, making it much harder for the blast fungus to find a way to take hold, says Talbot.
He says the Japanese researchers have made a big discovery with universal applicability. When this is combined with other methods of engineering rice, scientists may be in a position to “exclude blast infections in a durable manner”.
Fukuoka has also managed to isolate the resistant form of Pi21, meaning it can be separated from other genes associated with poor yield. Previously this has been difficult because when scientists have tried to transfer the resistant Pi21 gene into new strains of rice, the genes affecting quality have also hitched a ride.
Fukuoka says the fact that his research has shown the exact location of the Pi21 gene means scientists can ensure it is not replaced by a more vulnerable form when breeding new rice strains.
Copied from: PestNet
The “big rust’s” impact on coffee disease management Coffee rust has made significant headlines in recent years for its devastating effect on coffee crops. According to the United States Agency for International Development (USAID), losses in Latin America and the Caribbean alone have totaled well over $1 billion, causing hardship to coffee plantations, their labourers, coffee retailers, and the consumers who pay more for their morning coffee.
But this fungal disease, also known as “the big rust,” has a much longer and more encompassing history that goes all the way back to its discovery in 1869. This history is reviewed in detail through a new Phytopathology article entitled, “The Big Rust and the Red Queen: Long-Term Perspectives on Coffee Rust Research,” written by Stuart McCook, historian at the University of Guelph in Ontario, Canada, and John Vandermeer, professor of ecology and evolutionary biology at the University of Michigan, USA.
In this essay, the authors discuss the big rust in a broader historical context, chronicling coffee rust epidemics, the social and ecological conditions that produced them, and the evolving scientific responses to this threat. The article highlights the many innovations used to combat coffee disease outbreaks, such as the efforts to develop disease-resistant plants, chemical and agroecological control, and even a network of international coffee research institutes. It also incorporates the broader social and economic histories of coffee production into particular stories of rust epidemics and rust research. The article also points out examples of the current research and disease mitigation challenges in developing nations versus affluent parts of the world.
By taking this broad perspective, the authors suggest we are entering a new phase in the global history of the coffee rust.
“Up until the mid-1980s, the story of the coffee rust was largely the story of invasions, as the disease spread into regions where it was not previously present,” McCook said. “By the mid-1980s, however, the disease had reached almost every coffee-producing region in the world.”
“For a brief while, in the 1980s and 1990s, it looked as if coffee farmers-with the help of scientists-had adapted to the disease, making it ‘just another disease’ on the farm. But we suggest that this fragile equilibrium has begun to break down, both because of broader ecological changes that we are only beginning to understand, and also because of increasing volatility in the global coffee economy,” he said.
Read this paper in the September 2015 issue of Phytopathology.
(Phytopathology News, November 2015)
Mustapha El-Bouhssini (MS ’86, PhD ’92) Aleppo, Syria, is a global authority on plant resistance to insects in grains and has worked to develop crop varieties resistant to several important arthropod pests.
He recently received the Distinguished Scientist Award from the International Branch of the Entomological Society of America for significant contributions to entomological research.
El-Bouhssini serves as an adjunct faculty member in the Department of Entomology. This position has helped initiate collaborative projects between K-State and ICARDA on Hessian fly genetics and resistance in barley to the Russian wheat aphid.
From the KSU AgReport Spring 2015
New GM Rice Shows Improved Disease Immunity
09 April 2015
US – Rice disease immunity can be improved by transferred genes from other species, according to new research from the University of California-Davis.
Rice is well equipped with an effective immune system that enables it to detect and fend off disease-causing microbes.
However, the new study showed that immunity can be further boosted when the rice plant receives a receptor protein from a completely different plant species via genetic engineering.
Lead author Benjamin Schwessinger, a postdoctoral scholar in the UC Davis Department of Plant Pathology, said: “Our results demonstrate that disease resistance in rice, and possibly related crop species, could very likely be enhanced by transferring genes responsible for specific immune receptors from dicotyledonous plants into rice, which is a monocotyledonous crop.”
Immune receptors are specialised proteins that can recognise patterns associated with disease-causing microbes, including bacteria and fungi, at the beginning of an infection.
These receptors are found on the surface of plant cells, where they play a key role in the plant’s early warning system.
Some of the receptors, however, occur only in certain groups of plant species.
Mr Schwessinger and colleagues successfully transferred the gene for an immune receptor from the model plant Arabidopsis thaliana, a member of the mustard family, into rice.
The rice plants that produced the Arabidopsis immune receptor proteins were more resistant to Xanthomonas oryzae pv. oryzae, an important bacterial disease of rice.
This demonstrated that receptors introduced to rice were able to make use of the rice plants’ native immune signalling mechanisms and cause the rice plants to launch a stronger defensive immune response against the invading bacteria.