Botrytis is a genus of imperfect phytopathogenic fungi belonging to the Sclerotinicaeae family of the Ascomycota division. They develop in environments with a mild and humid climate, being the causative agent of the disease known as gray mold or gray rot.
It is a group of fungi with septate, branched and septate mycelium, which produce endogenous ascospores capable of infecting numerous economically important crops. The dark-gray mycelium with a spongy consistency on the damaged tissues is a particular characteristic of this group of fungi..
The wounds are the entrance door of its spores, once inside the host it causes the rotting of roots, stems, leaves, flowers, fruits, bulbs or tubers. It is considered a necrotrophic fungus, since it presents a parasitic and a saprophytic phase, since after killing the host it continues to feed on its remains.
Its presence is common in greenhouses or grow houses, where vegetables or fruit trees are produced under controlled conditions, including flowers and ornamental plants. Among the main crops that it infects, vegetables (artichoke, pumpkin, lettuce, tomato, paprika), fruit trees (citrus, strawberry, vine), and ornamental (carnations, geraniums, sunflower, rose, tulips) stand out..
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The mycelium is the vegetative part of the fungus, it is made up of multicellular, cylindrical and septate filaments of apical growth, known as hyphae. The gender Botrytis it is characterized by the production of a large number of asexual spores or oval conidia that are located at the end of the conidiophores.
The greyish conidiophores originate from the mycelium, although under certain circumstances they are formed from the sclerotia. Conidia are the main dispersal and reproduction structures of the fungus, being a structure that can survive in adverse conditions.
The conidia adhere to the plant surface, maintain their infective capacity and viability during the growth of the culture until they penetrate the host through a wound. Once installed, they generate a small vesicle from which the phialides arise, at the end of which the microconidia are produced..
Chlamydospores are formed after the transformation of the mycelium and are released when the hyphae disintegrate. They are hyaline in appearance and have a great variability in terms of shape and size, appear on aged tissues or contaminated cultures.
During the winter small nodules of firm consistency are formed, known as sclerotia, these are resistance structures that remain in hibernation. These are multicellular structures of a flat-convex shape 1-15 mm long by 1.5 mm wide that are formed in decomposed cultures..
The species of the genus Botrytis they are highly active even in environments with temperatures below 12 ºC. They generally cause great economic losses in crops stored for a long period of time under refrigerated conditions..
The spores do not directly penetrate the culture tissues, they do so through wounds caused by insect bites, hailstorms or pruning. For this reason, special care must be taken during harvest, since once the fungus penetrates it is difficult to eradicate it..
- Fungi kingdom
- Division: Ascomycota
- Subdivision: Pezizomycotina
- Class: Leotiomycetes
- Order: Helotiales
- Family: Sclerotinicaeae
- Gender: Botrytis
- Botrytis allii: plant pathogen that causes neck rot in stored onions.
- Botrytis cinerea or Botryotinia fuckeliana: species that affects horticultural and fruit crops such as citrus or vineyards.
- Botryotinia convoluta: kind of Botrytis affecting the rhizomes of ornamental species of the genus Iris.
- Botrytis fabae: species that causes the chocolate stain in bean crops (Vicia faba).
- Botryotinia polyblastis: fungal pathogen that attacks ornamental plants of the genus Narcissus.
Fungi belonging to the genus Botrytis they can be developed in two different ways. Hence, two different types of pathologies are considered:
It is the disease that develops within the host, which is why it is considered difficult to eradicate once installed. In general, it causes rotting of the internal tissues of the plant, the symptoms are difficult to detect and appear when the disease is very advanced..
The infection is carried out from the outside to the inside, being more frequent in ripe fruits than in tender fruits. It is easier to detect or eradicate, since symptoms can be detected with the naked eye, before they invade the internal tissues.
The first symptoms are manifested as dark spots on leaves and flowers, rotten fruit and necrotic tissues in bulbs or stored products. The fungus causes the rotting of the tissues of the affected organ and the progressive decay of the host until causing the death of the plant.
The species Botrytis cinerea It is the causal agent of gray rot in vine crops, causing the grapes to dry out. These symptoms decrease the sugar content and increase the solid elements, which substantially affects the viticultural quality of the crop..
It usually develops in environments with medium temperature and high relative humidity, its incidence being greater in times of rain or when the plant remains wet for a long time. In addition, if the crop presents some type of wound on stems, leaves or flowers, the presence of the pathogen will be unavoidable..
The symptoms can be seen with the naked eye, as there are watery spots and rots of the affected tissues. Over time, the affected surface becomes covered with a gray mold, the mycelium of the fungus, occasionally the plant can die.
The presence of Botrytis On soft fruits, such as tomato, paprika, strawberry, pumpkin or cucumber, even cut flowers, it substantially affects the commercial quality of the crop. Its incidence is favored by poor crop management, either poorly carried out pruning or a bad cut during harvest..
When the fungus affects a fruit such as tomato or strawberry, it must be discarded immediately, since they are not considered suitable for human consumption. The best prevention is to keep the crops well ventilated, in this way the humidity is prevented from remaining on the foliage for a long time..
- Use the appropriate planting density for each crop, avoiding crops that are too dense.
- Under greenhouse conditions control aeration, heating and irrigation frequency.
- Eliminate affected plants once they are detected.
- Use healing gels when doing some kind of pruning in the crop.
- Use certified seeds.
- Foliar applications with the fungus Trichoderma harzianum in case of detecting the pathogen, it can also be used as a disinfectant for seeds.
- The use of fungi of the genus Mucor, What M. corymbilfer, M. mucedo, M. pusillus or M. racemosus, has reported good results in the control of Botrytis during the early stages of infestation.
The application of fungicides to control Botrytis, many times to ineffective results once installed in the crop. However, it is recommended to apply fungicides based on Iprodione 50% (P / V), Vinclozolin 50% (WP) or Procymidone 50% (WP) together with a broad spectrum fungicide..
In the same way, it is advisable to carry out preventive treatments before starting flowering and to place fungal pastes on the blackened tissues. However, all chemical treatment must be accompanied by good agronomic management practices to reduce the probability of incidence of this disease..
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