''Phytophthora medicaginis'' is an oomycete

plant pathogen Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomyc ...

that causes

root rot Root rot is a condition in which anoxic conditions in the soil or potting media around the roots of a plant cause them to rot. This occurs due to excessive standing water around the roots. It is found in both indoor and outdoor plants, although ...

alfalfa Alfalfa () (''Medicago sativa''), also called lucerne, is a perennial flowering plant in the legume family Fabaceae. It is cultivated as an important forage crop in many countries around the world. It is used for grazing, hay, and silage, as w ...

and

chickpea The chickpea or chick pea (''Cicer arietinum'') is an annual legume of the family Fabaceae, subfamily Faboideae. Its different types are variously known as gram" or Bengal gram, garbanzo or garbanzo bean, or Egyptian pea. Chickpea seeds are high ...

. 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 megasperma'' is a species of water mould in the family Peronosporaceae. It is well known as a plant pathogen with many hosts. It often causes a plant disease called root rot.damping off of seedlings. ''P. medicaginis'' is specific to alfalfa and chickpea and can reside in soil or water, but since it is a water mold, it requires free water to infect another plant. This disease is most prevalent in newly seeded fields that experience flooding but can also be found in mature plants. ''P. medicaginis'' commonly causes seedling death but if this pathogen is present in mature crops, ''P. medicaginis'' causes root rot which limits the plant's ability to acquire nutrients and water. This leads to secondary symptoms such as chlorosis, wilting, stunting, root decay, lesions and death. This disease is difficult to identify but reddish-brown or black root lesions will exist and oospores,

sporangia A sporangium (; from Late Latin, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cy ...

zoospore A zoospore is a motile asexual spore that uses a flagellum for locomotion. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Diversity Flagella types Zoospores may possess one or mo ...

s, antheridia, and

oogonia An oogonium (plural oogonia) is a small diploid cell which, upon maturation, forms a primordial follicle in a female fetus or the female (haploid or diploid) gametangium of certain thallophytes. In the mammalian fetus Oogonia are formed in larg ...

are spore types that will be visible under a microscope. An

ELISA The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay uses a solid-phase type of enzyme immunoassay (EIA) to detect the presence ...

test can confirm the presence of ''Phytophthora'', but to confirm the species, a

PCR PCR or pcr may refer to: Science * Phosphocreatine, a phosphorylated creatine molecule * Principal component regression, a statistical technique Medicine * Polymerase chain reaction ** COVID-19 testing, often performed using the polymerase chain r ...

test is effective. Several host factors will affect disease development including damage/stress to the plant and also the degree of resistance of host cultivar.

Disease cycle

The disease cycle “starts” in the early spring as the oospores begin to germinate. Oospores are thick walled survival structures that allow the pathogen to survive winter. The oospores are then stimulated to germinate in the presence of free water and root exudates. Germination produces zoospores and sporangia which can then release more zoospores that infect other seeds. This is the asexual part of the cycle. This production of sporangia and zoospores happens until the end of the season when oogonia and antheridia engage in homothallic sexual reproduction to produce oospores once again. Spore types are disseminated via water such as during flooding. A cool environment also favors disease transmission.

Management

An integrated disease management program incorporating host resistance with disciplined cultural, chemical, and biological methods is the best way to control ''P. medicaginis''. The first several weeks are especially critical in the management of ''P. medicaginis'' as infected seeds die in a short amount of time. Control of alfalfa and chickpea is mostly possible using effective water management, use of resistant

cultivar A cultivar is a type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture, ...

s, proper

crop rotation Crop rotation is the practice of growing a series of different types of crops in the same area across a sequence of growing seasons. It reduces reliance on one set of nutrients, pest and weed pressure, and the probability of developing resistant ...

, and seed application of

fungicide Fungicides are biocidal chemical compounds or biological organisms used to kill parasitic fungi or their spores. A fungistatic inhibits their growth. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality, ...

s such as metalaxyl. Effective water management is aimed at keeping the plants as dry as possible while still getting them enough water. Several ways to do this include assuring good drainage, avoiding excessive

irrigation Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...

, and allowing plants to be dried by the wind. Oospores can be spread by way of cultural practices on machinery, boots, and hooves. This spread can be limited by using proper sanitation before moving from an infected field to a disease free field. All of these control methods are aimed at stopping the initial infection of the seed/plant; water management also functions to limit the spread of zoospores because they may be spread by floods. Stopping the initial infection is important because this disease affects plants early on in their development as it quickly causes root rot and damping off. ''P. medicaginis'' can reside in fields as oospores for up to 3.5 years so the crop rotation must be at least 3 years long.

References

External links

Index Fungorum

USDA ARS Fungal Database
{{DEFAULTSORT:Phytophthora Medicaginis medicaginis Water mould plant pathogens and diseases