''Pythium dissotocum'' is a plant pathogen infecting

strawberry The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown Hybrid (biology), hybrid plant cultivated worldwide for its fruit. The genus ''Fragaria'', the strawberries, is in the rose family, Rosaceae. The fruit ...

and

rice Rice is a cereal grain and in its Domestication, domesticated form is the staple food of over half of the world's population, particularly in Asia and Africa. Rice is the seed of the grass species ''Oryza sativa'' (Asian rice)—or, much l ...

Disease cycle

''Pythium dissotocum'' is a polycyclic oomycete root rot capable of both sexual and

asexual reproduction Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the f ...

. In its mid-season asexual phase, ''P. dissotocum'' disperses by forming filamentous sporangia, which produce vesicles housing 10-75 motile zoospores. Vesicles open, releasing zoospores which contact host roots, encyst, and produce a germ tube which infects the host root, and begins formation of mycelium. In sexual reproduction, if multiple mating types are present, hyphal antheridium can contact each other and undergo plasmogamy, merging their membranes near the end of growing season. After several steps of differentiation and meiosis, an oospore, the primary survival structure, is formed. These thick-walled oospores can remain dormant for many months, and will eventually germinate through two methods. A sporangium can be produced, which generates a cyst and releases zoospores, or the oospore can create a germ tube which can directly penetrate and infect a host. This disease cycle is extremely dependent on water for dispersal, making greenhouses, irrigation systems, and hydroponics especially prone to spread of ''P. dissotocum.''

Importance

''P. dissotocum'' is primarily a water-borne pathogen, and as a result poses serious threats to plants grown via

hydroponics Hydroponics is a type of horticulture and a subset of #Passive sub-irrigation, hydroculture which involves growing plants, usually crops or medicinal plants, without soil, by using water-based mineral Plant nutrition, nutrient Solution (chemi ...

and by

irrigation Irrigation (also referred to as watering of plants) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has bee ...

. With motile spores that can move quickly, infection spreads rapidly in water-logged crops and hydroponic systems. ''P. dissotocum'' can infect a large range of hosts, including many agricultural and horticultural crops like lettuce, spinach, peppers, parsnip, parsley, tomato, sugar cane, and carrot and hydroponic '' Cannabis sativa''. Other economic products are threatened by the presence of ''P. dissotocum'', including tree nurseries, maize/corn, and

soybean The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean. Soy is a staple crop, the world's most grown legume, and an important animal feed. Soy is a key source o ...

s. Infection of ''P. dissotocum'' can lead to significant loss of crop yield due to necrosis of roots, root lesions, chlorosis, and

damping off Damping off (or damping-off) is a horticultural disease or condition, caused by several different pathogens that kill or weaken seeds or seedlings before or after they germinate. It is most prevalent in wet and cool conditions. Symptoms There ar ...

. This results in severe economic loss for farmers growing both sustenance crops, and commercial products. The organism is found in many regions across the Americas, Europe, and Asia, meaning that increasing globalization could cause introduction of the pathogen to potentially vulnerable crops and ecosystems.

Diagnosis

RTPCR methods are available.

Control

As a root rot, it tends to have more severe effects on young plants and seedlings, where it can damage and kill newly forming roots necessary for plant growth and nutrient acquisition. As a result, many control methods involve limiting the amount of exposure early in the season. Effective measure include application of

fungicide Fungicides are pesticides used to kill parasitic fungi or their spores. Fungi can cause serious damage in agriculture, resulting in losses of yield and quality. Fungicides are used both in agriculture and to fight fungal infections in animals, ...

s like mefenoxam and phosphonates, often in conjunction. Additionally, inoculation with '' Pseudomonas chlororaphis,'' a common

biocontrol Biological control or biocontrol is a method of pest control, controlling pests, whether pest animals such as insects and mites, weeds, or pathogens affecting animals or phytopathology, plants by bioeffector, using other organisms. It relies o ...

inoculant used in

horticulture Horticulture (from ) is the art and science of growing fruits, vegetables, flowers, trees, shrubs and ornamental plants. Horticulture is commonly associated with the more professional and technical aspects of plant cultivation on a smaller and mo ...

, has potential to suppress symptoms of ''P. dissotocum'' infection, but is currently inconsistent in current trials, and doesn't block colonization. Like most root rots, ''P. dissotocum'' thrives in wet conditions. Preventing over-watering will help reduce infection in soil. Engaging in sanitation or fungicide treatment of tools and water can help reduce transmission and infection of ''P. dissotocum'' especially in irrigation or hydroponic systems. If infection has occurred, recovery can sometimes occur by trimming off damaged roots, and sterilizing those that are still white and healthy.

References

External links

USDA ARS Fungal Database
{{Taxonbar, from=Q7263879 dissotocum Water mould plant pathogens and diseases Water mould strawberry diseases Rice diseases Oomycete species Protists described in 1930