| Pyrenochaeta lycopersici | |
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| Tomato roots showing symptoms of corky root rot | |
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| Species: | P. lycopersici |
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| Pyrenochaeta lycopersici R.W. Schneid. & Gerlach, (1966) | |
Pyrenochaeta lycopersici is a fungal plant pathogen, infecting tomatoes and causing corky root rot.
The most susceptible host to Pyrenochaeta lycopersici is tomato, but the pathogen can also infect and cause damage to members of the families of Solanaceae and Cucurbitaceae such as pepper, eggplant, cucumber and melon. [1] [2] Wilt, stunting and lack of vigor can be observed as the primary symptoms, and infected leaves can possibly show interveinal chlorosis that leads to premature defoliation. [3] [4] The distinctive characteristic of P. lycopersici is that it causes brown lesions on the surface of medium roots which are known as a brown root rot. [4] In addition, the pathogen produces corky lesions on the large roots while rotting can be observed in the small roots. [2] Once the infection progresses, these lesions become wrinkled and dark brown, making cracks that prevent hosts from acquiring nutrients and water. [3] [5] These results are often followed by the root failure which causes the reduction of tomato yield. [3] [5]
Most of the disease cycle for Pyrenochaeta lycopersici is not completely understood. P. lycopersici is an ascomycete that has not been observed to have a teleomorph stage. [6] It has been discovered that the pathogen is capable of producing pycnidia that produce conidia on conidiophores within the pycnidia. [6] However, these pycnidia have never been observed on the infected plants in nature. P. lycopersici makes microsclerotia, which are survival structures, on the roots of host plants in soil. [3] [6] These microsclerotia can survive under harsh environments such as temperature changes and drought, and they can maintain the ability to infect other hosts in the soil for up to 15 years. [7] Once the environment becomes favorable for the pathogen growth, germination will occur in microsclerotia that leads to the production of hyphae. [6] The hyphae will penetrate and infect host roots through the epidermal cells. [3] [6] Approximately 48 hours after the primary infection, the infected cells begin to die, causing symptoms including necrosis. [6] P. lycopersici keeps infecting neighboring cells until the roots are completely colonized, and corky root lesions can be observed upon its completion. [6]
The suitable soil temperature for Pyrenochaeta lycopersici to initiate the infection is in the range between 15 and 20 °C. [8] [9] As the temperature increases above 18 °C, it is observed that there is less infection caused by the pathogen. [9] The corky root rot became one of the most serious diseases of tomato because growers used the inoculated soil without any type of disease management. [10] For instance, this occurred in Sweden when monoculture of tomatoes resulted in a yield reduction of 30-40%. [10]
Texas root rot is a disease that is fairly common in Mexico and the southwestern United States resulting in sudden wilt and death of affected plants, usually during the warmer months. It is caused by a soil-borne fungus named Phymatotrichopsis omnivora that attacks the roots of susceptible plants. It was first discovered in 1888 by Pammel and later named by Duggar in 1916.
Fusarium wilt is a common vascular wilt fungal disease, exhibiting symptoms similar to Verticillium wilt. This disease has been investigated extensively since the early years of this century. The pathogen that causes Fusarium wilt is Fusarium oxysporum. The species is further divided into formae speciales based on host plant.
Phytophthora sojae is an oomycete and a soil-borne plant pathogen that causes stem and root rot of soybean. This is a prevalent disease in most soybean growing regions, and a major cause of crop loss. In wet conditions the pathogen produces zoospores that move in water and are attracted to soybean roots. Zoospores can attach to roots, germinate, and infect the plant tissues. Diseased roots develop lesions that may spread up the stem and eventually kill the entire plant. Phytophthora sojae also produces oospores that can remain dormant in the soil over the winter, or longer, and germinate when conditions are favourable. Oospores may also be spread by animals or machinery.
Rhizoctonia solani is a species of fungus in the order Cantharellales. Basidiocarps are thin, effused, and web-like, but the fungus is more typically encountered in its anamorphic state, as hyphae and sclerotia. The name Rhizoctonia solani is currently applied to a complex of related species that await further research. In its wide sense, Rhizoctonia solani is a facultative plant pathogen with a wide host range and worldwide distribution. It causes various plant diseases such as root rot, damping off, and wire stem. It can also form mycorrhizal associations with orchids.
Aphanomyces euteiches is a water mould, or oomycete, plant pathogen responsible for the disease Aphanomyces root rot. The species Aphanomyces euteiches can infect a variety of legumes. Symptoms of the disease can differ among hosts but generally include reduced root volume and function, leading to stunting and chlorotic foliage. Aphanomyces root rot is an important agricultural disease in the United States, Europe, Australia, New Zealand, and Japan. Management includes using resistant crop varieties and having good soil drainage, as well as testing soil for the pathogen to avoid infected fields.
Thielaviopsis basicola is the plant-pathogen fungus responsible for black root rot disease. This particular disease has a large host range, affecting woody ornamentals, herbaceous ornamentals, agronomic crops, and even vegetable crops. Examples of susceptible hosts include petunia, pansy, poinsettia, tobacco, cotton, carrot, lettuce, tomato, and others. Symptoms of this disease resemble nutrient deficiency but are truly a result of the decaying root systems of plants. Common symptoms include chlorotic lower foliage, yellowing of plant, stunting or wilting, and black lesions along the roots. The lesions along the roots may appear red at first, getting darker and turning black as the disease progresses. Black root lesions that begin in the middle of a root can also spread further along the roots in either direction. Due to the nature of the pathogen, the disease can easily be identified by the black lesions along the roots, especially when compared to healthy roots. The black lesions that appear along the roots are a result of the formation of chlamydospores, resting spores of the fungus that contribute to its pathogenicity. The chlamydospores are a dark brown-black color and cause the "discoloration" of the roots when they are produced in large amounts.
Phytophthora cactorum is a fungal-like plant pathogen belonging to the Oomycota phylum. It is the causal agent of root rot on rhododendron and many other species, as well as leather rot of strawberries.
Phytophthora nicotianae or black shank is an oomycete belonging to the order Peronosporales and family Peronosporaceae.
Macrophomina phaseolina is a Botryosphaeriaceae plant pathogen fungus that causes damping off, seedling blight, collar rot, stem rot, charcoal rot, basal stem rot, and root rot on many plant species.
Pythium aphanidermatum is a soil borne plant pathogen. Pythium is a genus in the class Oomycetes, which are also known as water molds. Oomycetes are not true fungi, as their cell walls are made of cellulose instead of chitin, they are diploid in their vegetative state, and they form coenocytic hyphae. Also, they reproduce asexually with motile biflagelette zoospores that require water to move towards and infect a host. Sexually, they reproduce with structures called antheridia, oogonia, and oospores.
Verticillium dahliae is a fungal plant pathogen. It causes verticillium wilt in many plant species, causing leaves to curl and discolor. It may cause death in some plants. Over 400 plant species are affected by Verticillium complex.
Alternaria solani is a fungal pathogen that produces a disease in tomato and potato plants called early blight. The pathogen produces distinctive "bullseye" patterned leaf spots and can also cause stem lesions and fruit rot on tomato and tuber blight on potato. Despite the name "early," foliar symptoms usually occur on older leaves. If uncontrolled, early blight can cause significant yield reductions. Primary methods of controlling this disease include preventing long periods of wetness on leaf surfaces and applying fungicides. Early blight can also be caused by Alternaria tomatophila, which is more virulent on stems and leaves of tomato plants than Alternaria solani.
Phytophthora capsici is an oomycete plant pathogen that causes blight and fruit rot of peppers and other important commercial crops. It was first described by L. Leonian at the New Mexico State University Agricultural Experiment Station in Las Cruces in 1922 on a crop of chili peppers. In 1967, a study by M. M. Satour and E. E. Butler found 45 species of cultivated plants and weeds susceptible to P. capsici In Greek, Phytophthora capsici means "plant destroyer of capsicums". P. capsici has a wide range of hosts including members of the families Solanaceae and Cucurbitaceae as well as Fabaceae.
Rosellinia bunodes is a plant pathogen infecting several hosts including avocados, bananas, cacao and tea.
Pyrenochaeta terrestris is a fungal plant pathogen that infects maize, sweet potatoes, and strawberries. This plant pathogen causes a disease in onion that is commonly called pink root. P. terrestris is also known to infect shallots, garlic, leeks, chives, cantaloupe, carrots, cauliflower, cowpea, cucumbers, eggplants, lima beans, millet, oats, peas, peppers, potatoes, spinach, sugarcane, and tomatoes.
Colletotrichum coccodes is a plant pathogen, which causes anthracnose on tomato and black dot disease of potato. Fungi survive on crop debris and disease emergence is favored by warm temperatures and wet weather.
Septoria lycopersici is a fungal pathogen that is most commonly found infecting tomatoes. It causes one of the most destructive diseases of tomatoes and attacks tomatoes during any stage of development.
Ascochyta blights occur throughout the world and can be of significant economic importance. Three fungi contribute to the ascochyta blight disease complex of pea. Ascochyta pinodes causes Mycosphaerella blight. Ascochyta pinodella causes Ascochyta foot rot, and Ascochyta pisi causes Ascochyta blight and pod spot. Of the three fungi, Ascochyta pinodes is of the most importance. These diseases are conducive under wet and humid conditions and can cause a yield loss of up to fifty percent if left uncontrolled. The best method to control ascochyta blights of pea is to reduce the amount of primary inoculum through sanitation, crop-rotation, and altering the sowing date. Other methods—chemical control, biological control, and development of resistant varieties—may also be used to effectively control ascochyta diseases.
Buckeye rot of tomato is caused by three species of pathogens in the genus Phytophthora: P. nicotianae var. parasitica, P. capsici, and P. drechsleri. It is an oomycete that thrives in warm, wet conditions and lives in the soil. It is characterized by a bull’s eye pattern of dark brown rotting on the tomato fruit, and affects fruit that is close to, or lying on the soil. The easiest management is to keep the plant out of contact with the soil, although other chemical methods can be very effective. This disease commonly occurs in the southeast and south central areas of the United States. The disease has affected a large portion of crop yield in the United States as well as India. The relatively small genome size of Phytophthora parasitica compared to Phytophthora infestans gives researchers the unique ability to further examine its ability to cause disease.
Alternaria leaf spot or Alternaria leaf blight are a group of fungal diseases in plants, that have a variety of hosts. The diseases infects common garden plants, such as cabbage, and are caused by several closely related species of fungi. Some of these fungal species target specific plants, while others have been known to target plant families. One commercially relevant plant genus that can be affected by Alternaria Leaf Spot is Brassica, as the cosmetic issues caused by symptomatic lesions can lead to rejection of crops by distributors and buyers. When certain crops such as cauliflower and broccoli are infected, the heads deteriorate and there is a complete loss of marketability. Secondary soft-rotting organisms can infect stored cabbage that has been affected by Alternaria Leaf Spot by entering through symptomatic lesions. Alternaria Leaf Spot diseases that affect Brassica species are caused by the pathogens Alternaria brassicae and Alternaria brassicicola.