Phytophthora

 

Characteristics Of Phytophthora

ü Phytophthora is a genus of plant-damaging oomycetes, whose member species are capable of causing enormous economic losses on crops worldwide, as well as environmental damage in natural ecosystems.

ü The cell wall of Phytophthora is made up of cellulose.

ü Phytophthora species resemble true fungi because they grow by the means of fine filaments, called hyphae, and produce spores.

ü Their hyphae lack cross-walls, and the diploid phase, rather than the haploid phase, dominates their life cycle.

ü Another striking  feature of Phytophthora is that it produces swimming spores, called zoospores, during a phase of its lifecycle, a vestige of  its evolutionary origins in water.

Important species

ü There are currently more than 80 described species of Phytophthora worldwide, and the vast majority of them are plant pathogens.

ü Phytophthora species damage plants by killing tissues.

ü The symptom of foliar infection is called ‘blight’.

ü Infection on stems or twigs creates a ‘canker’, which may be localized or expand around the stem.

ü If  twings or branches are girdled by expanding cankers, ‘dieback’ results.

ü Phytophthora species can cause multiple symptoms such as ; root rot, wilt, collar rot, or sudden death also.

Diseases symptoms caused by Phytophthora

Wilt Disease

Canker Disease

Blight Disease

Die back disease

Phytophthora infestans

•      Phytophthora infestans is an oomycete or water mold, a fungus-like microorganism that causes the serious potato and tomato disease known as late blight or potato blight.

•      The pathogen is favored by moist, cool environments:

–     Sporulation is optimal at 12-18°C in water-saturated or nearly saturated environments

–    Zoospore production is favored at temperature below 15°C

–    Lesion growth rates are typically optimal at a slightly warmer temperature range of 20-24°C.

Symptom of leaf blight on the underside of a Potato

Phytophthora citricola

•      Plant Damage : Foliar leaf spots, shoot blight, root crown rot and root rot.

•      Multiple hosts : Pine ( Pinus) , Rhododendron, True firs ( Abies)

•      This pathogen survives as spores in soil or container media.

•      Infection :

–    This spreads from leaves or needles into branch   and eventually into the main trunk.

•      Occurrence :

–    Foliar disease is often found in both container and

       field nurseries that use overhead irrigation during

       the growing season

–    Root rot occurs in areas that are poorly drained or

       subject to flooding.

Phytophthora crown rot

 Phytophthora multivora

•      This is pathogenic to bark and cambium of  E. gomphocephala and  E. marginata

•      It is believed to be involved in the decline  syndrome of both eucalypt species within the tuart woodland in south-west Western  Australia.

 

Phytophthora multivora sp; West 

Phytophthora palmivora

•      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 disease caused by fungi and moulds in South India.

•      It occurs almost every year Mysore, North & South Kanara, Malabar and other areas.

Phytophthora nicotianae

•      This causes the heart rot, a disease characterized by yellowing, leaf tip die back, and tipping of the plant caused by rotting of the growing point.

•      The disease blackens the central leaves and makes them loose and easy to pull out of the plant.

•      The infection usually begins at the heart of the rosette, carried by splashing water, and often causing significant damage in poorly drained soils.

•       If the pineapple plants develop root rot, aboveground symptoms include stunting and low yield as the result of crop infection.

Symptoms of Phytophthora nicotianae in Pineapple

Phytophthora

Phytophthora fragariae

•      Phytophthora fragariae is a fungus-like plant pathogen that causes red stele, otherwise known as Lanarkshire disease, in strawberries and raspberries.

•      Symptoms of red stele can include a red core in the roots, wilting of leaves, reduced flowering, stunting, and bitter fruit.

Red stele in strawberry

Black root rot in strawberry

Phytophthora kernoviae

•      This is a plant pathogen that mainly infects European beech and Rhododendron ponticum.

•      It causes disease on the aerial parts of a wide range of species of trees, shrubs and other plants, including forest and woodland species.

•      Infection can lead to death of the host plant in some cases and it is highly destructive on some species.

Phytophthora kernoviae in European beech

Phytophthora kernoviae in Rhododendron

Phytophthora sojae

•      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.

Phytophthora sojae causing root rot in soyabean

Phytophthora Lifecycle