Citrus greening, a devastating disease, has reduced Florida citrus production by 70%, according to most accounts. Efforts to develop disease control methods have been stymied because scientists have been unable to culture the causal bacterial pathogen.
Scientists knew that plants wage chemical war against bacterial, viral and fungal infections. Now they’ve learned how to “vaccinate” tomato plants with a natural chemical to boost their defenses against a pest that makes leaves shrivel up and die.
The EU has published a list of 20 regulated quarantine pests qualifying as priority pests, including Xylella fastidiosa, the Japanesebeetle, the Asian long-horned beetle, Citrus greening and Citrus Black Spot, whose economic, environmental and social impact on EU’s territory is the most severe. Member States will have to launch information campaigns to the public, do annual surveys, prepare contingency plans, simulation exercises, and action plans for the eradication of these pests.
For the first-time we can take a molecular-level look at one of the world’s deadliest crop killers. The Luteoviridae are pathogenic plant viruses responsible for major crop losses worldwide. Transmitted by aphids, the viruses infect a wide range of food crops including cereals, legumes, cucurbits, sugar beet, sugarcane and potato.
Most plants have plenty of enemies, from insects and other grazing creatures to various diseases, droughts and many other stressors.
Plants respond to injuries or illnesses by initiating various defense measures. But a viral infection requires a completely different response than desiccation, of course.
To know more about its attacker, the cell relies on mechanical and chemical signals.
Scientists have long known that nodulation is important to plant health. Nodulation occurs when nodules, which form on the roots of plants (primarily legumes), form a symbiotic relationship with nitrogen-fixing bacteria that deliver nutrients to the plant. This process is a key part of sustainable agriculture and makes legumes an important source of protein for much of the world. However, recent research shows that nodulation might positively impact the plant’s microbiome in other ways.
An international research collaboration has successfully assembled the complete genome sequence of the pathogen that causes the devastating disease Asian soybean rust.
The research development marks a critical step in addressing the threat of the genetically-complex and highly-adaptive fungus Phakopsora pachyrhizi which has one of the largest genomes of all plant pathogens. Asian soybean rust has a devastating impact on soybean, an internationally important crop with 346 million tonnes produced globally.
In conditions favourable to its spread, the rust can destroy up to 90% of the soybean harvest. At present soybean growers in major areas of cultivation such as Latin America must use chemicals to protect crops.
The largest producer of the soybean is Brazil, where the combined cost of losses and disease control measures is US $2 billion per season.
The new dataset comprises the genome sequence of three isolates (K8108, MG2006 & PPUFV02) of which one has been assembled at chromosome level detail (PPUFV02). These three genomes will be hosted by the Joint Genome Institute and will be made available soon.
The three genomes will be repeat masked and annotated in the same way, to facilitate direct comparisons and inferences for the research community. This will enable researchers to study the molecular mechanisms of the pathogen, paving the way for breeding and engineering of disease-resistant crops.
The international consortium behind the project comprised 11 research and industry partners: The 2Blades Foundation, KeyGene, the Joint Genome Institute (JGI), Bayer, Syngenta, the Brazilian Company of Agricultural Research (Embrapa), l’Institut National de la Recherche Agronomique (INRA – France), the German Universities of Hohenheim and RWTH Aachen, The Sainsbury Laboratory, and the Federal University of Viçosa (Brazil).
The soybean rust pathogen is highly adaptive and disease resistance genes present in soybean have been overcome rapidly, and the pathogen is building resilience against the current generation of fungicides. These two factors leave few solutions for controlling the disease in the field.
Two of the three isolates that the consortium have sequenced are from Brazil, where the impact of soybean rust is a huge problem for farmers.
Phakopsora pachyrhizi has a highly complex genome, it is 60 times bigger than the yeast genome, composed of 93% repetitive elements and possesses two nuclei.
This complexity has delayed progress on the sequencing of this pathogen, and meant that high-end, next‐generation sequencing technologies were required to complete the task.
Given the importance of this disease, KeyGene made their PromethION machine (an industry first) and their sequencing and bioinformatics experts available pro bono. This way ultra-long DNA-sequencing reads of the pathogen and a high quality nanopore assembly were produced. This allowed Dr. Yogesh Kumar Gupta from the 2Blades group to generate a chromosome level assembly of the isolate PPUFV02, of which the DNA was provided by their long-term collaborator Prof. Sérgio Brommonschenkel at the Federal University of Viçosa (Brazil).
The consortium has also generated a transcriptome atlas of all the fungal structures and infection stages of the pathogen.
“Asian soybean rust is a critical challenge for soybean growers,” said Dr. Peter van Esse, leader of the 2Blades Group at The Sainsbury Laboratory, Norwich, one of the collaborators.
“A chromosome level genome assembly allows the scientific community to study, in unprecedented resolution, components of the pathogen that are critical for causing disease. This is a critical first step towards the design of transformative control strategies to combat this highly damaging pathogen.”
Peter van Esse
Access the sequence: Mycocosm
Article source: The Sainsbury Laboratory
Image credit: U. Steffens, Bayer Crop Science
New research shows that ants inhibit at least 14 different plant diseases. The small insects secrete antibiotics from glands in the body. On their legs and body, they also host colonies of bacteria that secrete antibiotics.
Removing dead trees from the forests and reforesting on a large scale: this is the German Federal Government’s strategy against “Forest Dieback 2.0”. Scientists call for other solutions.
Evolutionary biologists have identified how herbicide-resistant strains of common waterhemp, an invasive weed, have emerged in fields of soy and corn in southwestern Ontario.
