Aphanomyces cochlioides | |
---|---|
Scientific classification ![]() | |
Domain: | Eukaryota |
Clade: | Diaphoretickes |
Clade: | SAR |
Clade: | Stramenopiles |
Phylum: | Oomycota |
Order: | Saprolegniales |
Family: | Leptolegniaceae |
Genus: | Aphanomyces |
Species: | A. cochlioides |
Binomial name | |
Aphanomyces cochlioides Drechsler, (1929) | |
Synonyms | |
Aphanomyces cochlioides is a plant pathogen that can affect commodity crops like spinach, Swiss chard, beets and related species. In spinach the pathogen is responsible for the black root "rot" that can damage plants.
Most commonly infection occurs on older roots that have already began to grow, but if infection of a younger root occurs it can be identified by the excess growth of lateral roots- which is a common plant response to loss of the main taproot. [1] Infection symptoms above ground will include chlorotic, non-vigorous, leaves that will not maintain turgor during the stress of hot sun, but will maintain the ability to revive during less stressful times such as cloudy days or overnight. [2] To discern from other common beet revive during less stressful times such as cloudy days or overnight. To discern from other common beet diseases such as Rhizoctonia or Pythium root rot, leaves can be tested for brittleness or a burned or scorched appearance. [3] It is also uncommon for a plant infected with Alternaria to become permanently wilted which is often the case in the previously mentioned pathogens. below ground root growth is often stunted as a result of lesions. The lesions have a water-soaked appearance and might be superficial. As the disease progresses down the stem and into the root the water-soaked spots will become darker as well as the interior of the root. An infected root will often have rotting around the tip laving behind only vascular bundles, classifying it as a tip rot. [4] If conditions for the plant are favorable it is possible for the crop to recover; however the root will still show signs of the infection such as dark spots, or scarring. There is an acute phase of the disease known as black root. This occurs April through June and will affect the younger plants. This can be especially devastating if warm, moist, conditions prevail in which seedlings can be destroyed within three to four days. The chronic phase, or root rot, occurs June through August in the latter part of the season in which the plants survived the first round of infection. This will be characterized by the wilt-recovery cycle of leaves and the root turning black from the inside out.
The pathogen Aphanomycete cochlioides, like most oomycete fungi, survives and overwinter as oospores in plant debris or soil. When the soil warms in the spring the oospores receive signals to germinate. The oospores have the ability to directly infect the root in the soil but it is more common for the oospore to play a smaller role in the life cycle producing a specialized hyphae called sporangium. The sporangium has the ability to produce zoospores- which have two different types of flagella, tinsel and whiplash, that allow them to be motile in soil water. These motile spores will move on to infect a root in the soil. Throughout the season if conditions are warm and wet enough the sporangium will continue to make more zoospores which can go no to infect other roots. It is within an infected root that additional oospores will be produced to overwinter another season. [5] Although disease develops in less heavy soils, a heavy textured soil is favorable as they tend to remain wetter. The same is true for low parts of fields, heavily compacted areas, or at the bottom of hills.
For early prevention of infection and to reduce the incidence of damping off, planting seeds that are at least partially resistant to Aphanomycete cochlioides is suggested. [6] You can also purchase and plant seeds that have been treated with Hymexazol which is a fungicide that has been proven to be effective in preventing early infection. Cultural practices are some of the most beneficial in stopping the spread of the pathogen. It is important to reduce cross contamination from equipment and tools. Removing dead and diseased tissue as well as clearing the field at the end of the season can help lower the amount of inoculum present the next season. Utilizing soil tiling practices can help soil drainage, as well as planting in an area that will not stay wet for an extended amount of time. Rotating crops can decrease the overwintering structures still viable when the next rotation occurs. Planting when the soil is cool has been shown to help give the seedlings a head start on growth before sporulation is triggered by warming temperatures.
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.
Phytophthora palmivora is an oomycete that causes bud-rot of palms, fruit-rot or kole-roga of coconut and areca nut. These are among the most serious diseases caused by fungi and moulds in South India. It occurs almost every year in Malnad, Mysore, North & South Kanara, Malabar and other areas. Similar diseases of palms are also known to occur in Sri Lanka, Mauritius, and Sumatra. The causative organism was first identified as P. palmivora by Edwin John Butler in 1917.
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.
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 medicaginis is an oomycete plant pathogen that causes root rot in alfalfa and chickpea. It is a major disease of these plants and is found wherever they are grown. P. medicaginis causes failure of stand establishment because of seedling death. Phytophthora medicaginis is part of a species complex with Phytophthora megasperma.
Phytophthora nicotianae or black shank is an oomycete belonging to the order Peronosporales and family Peronosporaceae.
Pythium irregulare is a soil borne oomycete plant pathogen. Oomycetes, also known as "water molds", are fungal-like protists. They are fungal-like because of their similar life cycles, but differ in that the resting stage is diploid, they have coenocytic hyphae, a larger genome, cellulose in their cell walls instead of chitin, and contain zoospores and oospores.
Phytophthora erythroseptica—also known as pink rot along with several other species of Phytophthora—is a plant pathogen. It infects potatoes causing their tubers to turn pink and damages leaves. It also infects tulips (Tulipa) damaging their leaves and shoots.
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.
Pythium graminicola is a plant pathogen infecting cereals.
Pythium myriotylum is a soil-borne oomycete necrotroph that has a broad host range, this means that it can infect a wide range of plants.
Pythium volutum is a plant pathogen infecting wheat, barley, and turfgrass. It is known to be sensitive to some of the compounds typically present in selective media commonly used for isolating Pythium spp., so isolation may require alternative methods.
Albugo occidentalis, the causal agent of spinach white rust, is an oomycete plant pathogen, although some discussions still treat it as a fungal organism. Albugo occidentalis is one of the most important spinach diseases in North America, found throughout the United States east of the rocky mountains.
Albugo is a genus of plant-parasitic oomycetes. Those are not true fungi (Eumycota), although many discussions of this organism still treat it as a fungus. The taxonomy of this genus is incomplete, but several species are plant pathogens. Albugo is one of three genera currently described in the family Albuginaceae, the taxonomy of many species is still in flux.
Pythium dissotocum is a plant pathogen infecting strawberry and rice.
Peronosclerospora sorghi is a plant pathogen. It is the causal agent of sorghum downy mildew. The pathogen is a fungal-like protist in the oomycota, or water mold, class. Peronosclerospora sorghi infects susceptible plants though sexual oospores, which survive in the soil, and asexual sporangia which are disseminated by wind. Symptoms of sorghum downy mildew include chlorosis, shredding of leaves, and death. Peronosclerospora sorghi infects maize and sorghum around the world, but causes the most severe yield reductions in Africa. The disease is controlled mainly through genetic resistance, chemical control, crop rotation, and strategic timing of planting.
This article summarizes different crops, what common fungal problems they have, and how fungicide should be used in order to mitigate damage and crop loss. This page also covers how specific fungal infections affect crops present in the United States.
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.
Black rot on orchids is caused by Pythium and Phytophthora species. Black rot targets a variety of orchids but Cattleya orchids are especially susceptible. Pythium ultimum and Phytophthora cactorum are known to cause black rot in orchids.