With the help of new genomic sequencing and assembly tools, plant scientists can learn more about the function and evolution of highly destructive plant pathogens that refuse to be tamed by fungicides, antibacterial, and antivirals.
Botanists have long held a fascination for heterotrophic plants, not only because they contradict the notion that autotrophy (photosynthesis) is synonymous with plants, but also because such plants are typically rare and ephemeral. However, it is still a matter of debate as to how these plants obtain nutrition.
Many New York tomato growers are familiar with the scourge of bacterial canker – the wilted leaves and blistered fruit that can spoil an entire season’s planting. For those whose livelihoods depend on tomatoes, this pathogen – Clavibacter michiganensis – is economically devastating.
In a new paper, Cornell researchers showed that wild tomato varieties are less affected by bacterial canker than traditionally cultivated varieties. The paper, “Characterizing Colonization Patterns of Clavibacter michiganensis During Infection of Tolerant Wild Solanum Species,” published online in the journal Phytopathology.
Co-authors were Christine Smart, professor of plant pathology and plant-microbe biology in the College of Agriculture and Life Sciences; F. Christopher Peritore-Galve, a doctoral student in the Smart Lab; and Christine Miller, a 2018 Smart Lab undergraduate summer intern from North Carolina State University.
“Bacterial canker is pretty bad in New York,” Peritore-Galve said, “but it’s distributed worldwide, everywhere tomatoes are grown.”
The pathogen causes wounding and is spread by wind-blown rain; if one tomato gets infected, it can spread from plant to plant.
“Bacterial canker certainly can cause the complete loss of a field of tomatoes, and we see outbreaks of the disease every year,” Smart said. “Growers use disease management strategies, including spraying plants with copper-based products; however, once there is an outbreak it’s difficult to control bacterial canker.”
To combat diseases, plant pathologists and breeders often look for varieties that are resistant, but among tomatoes traditionally grown for market, there are none with genetic resistance to bacterial canker. So Peritore-Galve, Miller and Smart went back to the beginning.
Tomatoes are native to the Andes Mountains region of South America, where wild species have been free to evolve for thousands of years. Recently, plant breeders have identified wild tomatoes that seem to be less susceptible to bacterial canker and are resistant to other pathogens.
The team wanted to understand how bacteria spread and colonize in wild tomatoes versus cultivated ones. They zeroed in on the plants’ vascular systems – specifically their xylem vessels.
Like individual veins in a human, xylem vessels transport water and nutrients from soil throughout the plant. The team found that in cultivated species, bacterial canker spreads everywhere, while in wild species the bacteria remain confined to certain xylem vessels without moving much into surrounding tissues.
“The wild tomatoes, for some reason, impede the ability of the bacteria to move up and down through the plants, which reduces symptoms – in this case, leaf wilt,” Peritore-Galve said.
This is the first study ever confirming that wild tomatoes are susceptible to bacterial canker, though the infection is less severe than in cultivated varieties. But while a severe infection causes fewer symptoms in the wild plant, it can still cause lesions on the fruit.
Even so, a tomato variety with resistance to the bacteria could still be very helpful for tomato growers, said Chuck Bornt, vegetable specialist with Cornell Cooperative Extension’s Eastern New York Commercial Horticulture program. Bornt works extensively with New York tomato growers.
“Many times, it’s not the fruit symptoms that cause the issue,” Bornt said, “it’s the wilting of the plants or the plugging of the xylem cells that cause the plant to lose foliage, which then exposes the fruit to sun scald and other issues. … Infected fruit are also an issue, but in my opinion it’s these other issues that have more impact.”
Read the paper: Phytopathology
Article source: Cornell University
Author: Krisy Gashler
Image credit: Allison Usavage/Cornell University
For long, it was assumed that cell death occurs mainly during animal organ growth but not in plant organs. A research group demonstrated now that the death of certain cells in the root facilitated the growth of lateral roots. These new findings hint at organ growth of plants and animals might not be so different as thought.
Blue-green-algae outbreaks have major impacts on plants and animals that live in or near creeks, rivers, lakes, estuaries and the ocean. These algae can also produce toxins with major human health concerns. Now ,researchers have shown that leaf litter can play an important role in controlling algal blooms.
Researchers have discovered a new gene that improves the yield and fertilizer use efficiency of rice.
While studies of the microbiomes (which comprises all the microorganisms, mainly bacteria and fungi) of the phyllosphere and the rhizosphere of plants are important, scientists at INRA believe more attention should be given to the microbiomes of crop residues.
Crop residues are important as a key microbial ecosystem with the power to contribute both negatively and positively to crop health and productivity. Crop residues are a breeding ground for plant disease but also contribute significantly to the stability of agrosystems.
“Residues deserve special attention in the context of crop protection,” plant pathologist Frédéric Suffert explains. “First, because residues are ‘the problem’ as the main support of pathogens that cause disease. Second because residues can be also part of the solution to control these diseases.”
Focusing on cereal crops, the INRA scientists explored how dynamic interactions between microbial communities of residues can contribute to innovative disease management strategies such as next-generation microbiome-based biocontrol.
“We connected residue microbiome with the survival of residue-borne fungal plant pathogens by combining knowledge in microbial ecology and epidemiology,” explained Frédéric Suffert. “This is the first time this connection has been made.”
Read the paper: Phytobiomes
Article source: American Phytopathologycal Society via Eurekalert
Image credit: Shutterbug75 / Pixabay
Scientists have made a significant discovery about the genetic origins of how plants evolved from living in water to land 470 million years ago.
In the face of rapid climate change, it is important that plants can adapt quickly to new conditions to ensure their survival. Using field experiments and plant genome studies, an international research team has pinpointed areas of the genome that are affected during local adaptation to contrasting climates. This new insight into local adaptation represents an important first step towards future development of crops that are resilient to climate change.
It is an open question how we can ensure that our crop plants remain productive in a changing climate. Plants are confronted with similar climate adaptation challenges when colonising new regions, as climate conditions can change quickly across latitudes and landscapes. Despite the relevance of the question, there is very limited basic scientific insight into how plants tackle this challenge and adapt to local climate conditions. Researchers from Denmark, Japan, Austria and Germany have now published the results of their research on this very subject.
The researchers studied the plant Lotus japonicus, which – with relatively limited genomic changes – has been able to adapt to diverse Japanese climates ranging from subtropical to temperate. Using a combination of field experiments and genome sequencing, the researchers were able to infer the colonisation history of L. japonicus in Japan and identify areas in the genome where plant populations adapted to warm and cold climates, respectively, showed extreme genetic differentiation. At the same time, they showed that some of these genomic regions were strongly associated with plant winter survival and flowering.
This is the first time researchers have identified specific genomic regions that have changed in response to natural selection to allow the plant species to adapt to new climatic conditions.
Professor Mikkel Heide Schierup states: “One of the great questions of evolutionary biology is how natural selection can lead to genetic adaptation to new environments, and here we directly observed an example of this in Lotus japonicus.”
And Associate Professor Stig Uggerhøj Andersen adds: “Yes, and it is fascinating that we have identified specific traits, including winter survival, that have been under selection during plant local adaptation to contrasting climates. At the same time, we observed extreme genetic signatures of selection in specific genomic regions. This link between selection signatures and specific traits is critical for understanding the process of local adaptation.”
“The rapid adaptation of L. japonicus to widely different climates indicates that genetic variation underlying the adaptations was already present before plant colonisation. This is promising for other plant species on a planet with rapid climate change, since it will allow more rapid adaptation,” adds Professor Schierup.
“In this case, the different climates have resulted in distinct plant populations adapted to their own local environments. These populations appear to be preserved because certain genotypes are an advantage in warm climates, but a disadvantage in cold climates and vice versa,” concludes Dr. Andersen.
Read the paper: Nature Communications
Article source: Aarhus University
Author: LISBETH HEILESEN
Image credit: Niels Sandal, Aarhus University
New research identifies a protein that controls plant growth — good news for an era in which crops can get crushed by climate change.
