Glomerella cingulata facts for kids
Quick facts for kids Glomerella cingulata |
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| Symptoms of bitter rot on California laurel caused by the fungus Colletotrichum gloeosporioides | |
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Glomerella
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| Species: |
cingulata
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Glomerella cingulata is a tiny living thing called a fungus. It's a type of plant pathogen, which means it can make plants sick. This fungus has two names: Glomerella cingulata is its "sexual" stage, and Colletotrichum gloeosporioides is its more common "asexual" stage.
For most of this article, we'll call it C. gloeosporioides. This fungus causes big problems for plants all over the world. It leads to diseases like anthracnose and fruit rot on hundreds of important plants.
Contents
Hosts and Symptoms
C. gloeosporioides can infect many different plants. It causes anthracnose disease on crops like cereals, grasses, legumes, fruits, vegetables, and trees. It has even been found infecting harvested durian fruit.
Scientists think that there might be different types of C. gloeosporioides that prefer certain plants. The signs of the disease can look different depending on the plant. But usually, you'll see wet, sunken spots on fruit. These spots turn dark and dead as the disease gets worse. Leaves might get small, dark spots too.
Let's look at mangoes as an example, since they are an important fruit. On mangoes, fruit symptoms appear late in the season, as the fruit gets ripe. The fruit develops large, sunken areas that are dark brown or black. Sometimes, the fruit can even crack open. This happens when dark lines turn into deep cracks through the skin and into the fruit's soft inside.
Because symptoms aren't seen before the fruit ripens, mangoes can look healthy when picked. But they can quickly get sick in storage or during shipping. Mango leaves show small, dark spots that grow bigger as the disease spreads. While symptoms vary, mangoes give a good idea of what this fungus generally does.
On chestnuts, the disease can also be called blossom end rot. You might first see the chestnut burs (the spiky outer shell) turning brown at the blossom end in August. When it's time to harvest, the pointed end of the chestnut shell and the nut inside will be black. The amount of blackening can be different. It might be just a tiny black tip or the whole nut. Parts of the nut that aren't black can still be eaten.
No matter the plant, C. gloeosporioides leaves clues that help us identify it. If you look at sick plant tissue under a microscope, you might see orange or pink spots called acervuli. These are where the fungus makes its spores. They often have black, hair-like spikes sticking out. Under a stronger microscope, the spores look oval-shaped.
On some plants, the sexual stage of the fungus (G. cingulata) makes small, flask-shaped structures called perithecia. These are full of tiny sacs that hold spores. If you grow the fungus in a lab on a special food called potato dextrose media, it can look gray, orange, or pink. It often grows in rings, like a target. Scientists can also identify C. gloeosporioides using DNA tests if they have the right equipment.
Importance
The money lost because of C. gloeosporioides changes depending on the plant it infects. But because it harms some very important crops, it's a big worry for farmers worldwide.
For example, in strawberries grown in China, C. gloeosporioides (along with two other similar fungi) can cause up to 80% of young plants to die in nurseries. It can also lead to over 40% of the crop being lost in fields. In these two examples alone, this fungus causes millions of dollars in losses.
Classification
Recent studies suggest that C. gloeosporioides might actually be many different species. This is because it acts differently on various plants. Scientists are using genetic analysis to study the fungus. They have found enough differences in its DNA to suggest it needs a more specific classification. Work is being done to create a new system for what is now called the "C. gloeosporioides complex."
Life Cycle
The way this disease spreads depends on which form of the fungus is present. This affects how the fungus survives when there isn't a plant to infect.
If the sexual stage (G. cingulata) is there, the fungus reproduces sexually. It forms ascospores inside special sacs, which are packed into perithecia. This creates new types of the fungus and helps it survive tough times. If only the asexual stage (C. gloeosporioides) is present, the fungus must survive inside sick plant tissue or on another plant.
When the conditions are right (like high humidity and warm temperatures, around 25–28 °C), the ascospores are released. Sick plant tissue also makes more spores called conidia. These conidia are spread by rain splash or wind to new parts of plants. They can infect leaves, young fruit, or blossoms.
Once a plant is infected, the fungus keeps making more conidia throughout the growing season. This means the disease can spread many times. When the host plant starts to get old, the sexual form of the fungus (G. cingulata) will make ascospores in perithecia. This helps the cycle start all over again.
How it Attacks Plants
C. gloeosporioides is a hemibiotroph. This means it lives partly like a parasite (feeding on living plants) and partly like a saprophyte (feeding on dead plant material). The fungus prefers a living plant. But if the plant tissue dies, or if the fungus is in the soil without a host, it can switch to feeding on dead plant parts.
When a C. gloeosporioides spore lands on a plant in the right conditions, it first makes a special structure called an appressorium. This structure helps the fungus push its way through the plant's outer layer and cell wall. After getting inside, the fungus makes infection vesicles. These structures take nutrients from the plant. Later, when the infected fruit or leaves die, the fungus switches to feeding on the dead tissue.
Environment
This fungus grows best when it's warm, around 25–30 °C. It also needs high humidity, more than 95%, and a slightly acidic soil (pH of 5.8 to 6.5). The disease can still happen in a wider temperature range, from 20–30 °C.
The fungus only releases its spores when there's a lot of moisture. So, C. gloeosporioides is not active during dry seasons. Direct sunlight, very hot or very cold temperatures, and low humidity can all make the spores inactive. These factors can stop the spores by themselves, or they can work together to have the same effect.
Management
How to control this fungus depends on the plant it's infecting. But there are some general farming practices that are very helpful.
Since C. gloeosporioides spores are spread by rain splash, it's good to avoid watering plants from above. If the farm is small enough, a farmer might even use a cover to keep rain off the plants. Trimming and thinning out plant material can help air move better. This stops high moisture conditions that the disease needs to spread. Also, to start with healthy plants, farmers should only use certified, disease-free young plants.
To stop fruit from rotting after harvest, fruit are often dipped in hot water or coated with wax. These methods can reduce the disease, but they don't completely stop C. gloeosporioides infection after harvest.
For chemical control, farmers can use broad-spectrum fungicides like chlorothalonil or mancozeb. These can be sprayed at the start of the growing season to prevent infection. Often, once fruit starts to grow, more fungicide sprays might just hide the symptoms until after harvest. During post-harvest treatment, harvested fruit are often coated with fungicides like phenols or benzimidazoles. This gives extra protection against rot, especially for fruit being shipped far away.
Both good farming practices and chemical treatments need to work together. This helps farmers create a safe and effective spraying plan. Scientists have even built a system that uses humidity and temperature to predict when this fungus will be most active. Using this system, farmers can plan the best time to spray to control C. gloeosporioides.
