Phytophthora palmivora

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Phytophthora palmivora
Phytophthora blight of papaya (5794539135).jpg
Mycelium associated with snail or slug feeding and bird feeding injury to papaya near Kainaliu, Hawaiʻi
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Clade: Diaphoretickes
Clade: SAR
Clade: Stramenopiles
Phylum: Oomycota
Order: Peronosporales
Family: Peronosporaceae
Genus: Phytophthora
Species:
P. palmivora
Binomial name
Phytophthora palmivora
Synonyms

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. [2]

Contents

Biology

Phytophthora palmivora produces abundant sporangia on V8 agar under continuous fluorescent light. However, light is not required for sporangia production on infected papaya fruit. Sporangia are usually produced in clusters sympodially. Sporangia are papillate and ovoid with the widest part close to the base. They are easily washed off and each detached sporangium contains a short pedicel. The average size of the sporangia is 50×33 µm with a length of about 1.6 times longer than it is wide. Sporangia germinate directly in a nutrient medium by producing germ tubes that develop into mycelial masses. In water, however, zoospores are released from germinating sporangia. Zoospores aggregate and form distinct patterns at 16 °C (61 °F) in water.[ citation needed ]

Chlamydospores produced in infected papaya fruit and pure papaya juice are thick-walled. However, chlamydospores produced in papaya juice at lower concentrations or in other kinds of fruit juice are mostly thin-walled. In the presence of nutrients, chlamydospores germinate by producing germ tubes that continue to grow and form mycelial masses. In water, chlamydospores germinate by producing short germ tubes, each with a sporangium at the tip.[ citation needed ]

Sexual reproduction in P. palmivora requires the presence of opposite mating types known as A1 and A2. Both A1 and A2 isolates can produce zoospores by selfing when stimulated by sex hormones produced by A2 and A1, respectively. Light is inhibitory to zoospore formation but stimulatory to zoospore germination. Mature zoospores can be induced to germinate by treatment with 0.25% KMnO4 for 20 min and incubation under light during germination.[ citation needed ]

Although sporangia and zoospores may survive in soil for short periods, chlamydospores are the main survival structure for P. palmivora in nature. Zoospores are capable of long-term survival but do not play a significant role in the disease cycle because sexual reproduction in P. palmivora requires the presence of opposite mating types, and the chance for this to occur in nature is very low.[ citation needed ]

During rainy periods, chlamydospores in soil may germinate in water to produce sporangia and release zoospores. The impact of falling rain drops may splash zoospores into air in droplets. The zoospore-containing droplets may be further dispersed by wind and become the inoculum for infecting fruit and occasionally stems of papaya in the fields. The pathogen produces abundant sporangia on the surface of infected fruit that are further dispersed by wind-blown rain and cause outbreaks of Phytophthora fruit rot in the same and nearby orchards. Chlamydospores formed in fallen fruit survive in soil and serve as the main source of inoculum for infection of roots of papaya seedling in subsequent plantings.[ citation needed ]

Phytophthora root rot of papaya seedlings is most serious during rainy periods. Under waterlogged conditions, P. palmivora may attack roots of papaya older than three-months of age, the time at which they become resistant to the pathogen under normal conditions. Therefore, Phytophthora root rot may occur on papaya at any age in poorly drained areas. Waterlogged conditions appear to weaken the defense mechanism of papaya roots against invasion by the pathogen. Mobility of zoospores of P. palmivora under such conditions also may contribute to the severity of the disease due to their attraction by papaya roots.[ citation needed ]

Favorable temperature is also a contributing factor to the severity of Phytophthora diseases because of its effect on growth and sporulation of the pathogen. P. palmivora has an optimum temperature for growth of 30 °C (86 °F), a maximum temperature of 36 °C (97 °F) and a minimum temperature of 12 °C (54 °F). The pathogen produces the most sporangia at 25 °C (77 °F) but no sporangia are produced at temperatures higher than 35 °C (95 °F) or lower than 15 °C (59 °F).

Hosts and symptoms

Although the common name of Phytophthora palmivora is bud rot of palms, and its Latin name means "plant destroyer" and "palm eater", it affects many tropical plants and has a moderately broad host range. P. palmivora is well studied in coconuts and papaya trees, however there are multiple hosts that are less commonly studied. One common symptom of P. palmivora is fruit rots which are found in papaya, citrus, coconuts, durian, and cacao. Root rots are another symptom of P. palmivora and can be seen in red maples, citrus, papaya, mango, durian, and black pepper. Another symptom is the presence of cankers which are found in red maple, papaya, rubber, mangos, and cacao. Bud rots can also be seen in papaya and coconuts infected with P. palmivora. Bud rots are also found in Palmyra palms and coconut palms. Collar rots are found on citrus, mango, and black pepper infected with P. palmivora. The signs of P. palmivora are microscopic and can be differentiated from other oomycetes by the presence of oval shaped papillate sporangia with short pedicles and spherical oogonia with narrow stalks (Widmer, 2014). [3]

Epidemiology

Rain and wind are the two major factors in the epidemiology of Phytophthora fruit rot of papaya. Rain splash is needed for liberation of sporangia of P. palmivora from the surface of infected fruit into the atmosphere and for projection of the soil inoculum into air. Wind is required for dispersal of the inoculum once it reaches the air. Therefore, wind-blown rain is essential for initiation of the primary infection and the development of epidemics in papaya orchards. P. palmivora also cause fruit rot, bud rot, etc. in coconut. Bud rot of coconut (Cocos nucifera) is very common in India.[ citation needed ]

Atmospheric temperature of 18–20 °C (64–68 °F) along with high humidity activates the pathogen.[ citation needed ]

Management

General control

Since P. palmivora is an oomycete the simplest management technique is to control the amount of water present in the soil. Techniques for controlling moisture include: monitored watering, pruning to increase airflow and decrease humidity in the soil, as well as making sure that areas where potential hosts are planted are not prone to flooding, oftentimes this includes planting on an incline. Other means of cultural control for P. palmivora include mulching to reduce the number of spores released via rain splash, complete removal of infected host plants and materials, and in some cases the use of companion crops. Companion crops are planted in the same fields as the host plant and are used to divert some of the pathogen away from the hosts, an example being planting bananas and avocados in the same field. Chemical control methods for P. palmivora include: protectant fungicides such as the Bordeaux mixture, phosphonates which control the mycelial growth of the pathogen, dithiocarbamates such as Mancozeb, and phenylamides which control the spread of the pathogen from the roots of the host. Host resistance is also a method of controlling the pathogen, resistant plants generally have thicker cuticles which inhibits the ability of the pathogen to enter the host.[ citation needed ]

Non-chemical control in papaya

Root rot of papaya seedlings, caused by P. palmivora, in replant fields can be controlled with the virgin soil technique. Virgin soil (soil in which papaya has never been grown in before) is placed in planting holes about 30 cm (12 in) in diameter and 10 cm (3.9 in) deep with a mound about 4 cm (1+9⁄16 in) high. Roots of papaya plants are protected by the virgin soil during the susceptible stage, and become resistant to the pathogen when they extend to the infested soil. Trees established with the virgin soil method in the replant fields produce fruit as abundantly as those growing in the first planting fields. The virgin soil method has the advantages of being relatively inexpensive, very effective and nonhazardous.[ citation needed ]

Cultural practice is also important in the management of Phytophthora diseases of papaya. Incidence of Phytophthora root rot of mature trees in waterlogged areas during the rainy periods can be greatly reduced by improving drainage in the orchards. Infected fruit on the trees and those that have fallen to the ground should be removed to reduce the inoculum for aerial infection of fruit and stems, and infection of seedling roots in subsequent plantings.[ citation needed ]

Genetic management

Medicago spp. including alfalfa may be resistant. [4] : 126  Wang et al., 2012 discovers an alfalfa mutant ram2 with impaired glycerol-3-phosphate acyltransferase. [4] : 126  This impairs its own cutin formation but also provides resistance because P. palmivora uses its products as a virulence signal. [4] : 126 P. palmivora suffers disrupted appressorial development due to its failure to receive as much of this signal. [4] : 126 

Importance

Because P. palmivora infects multiple hosts that hold an economic significance including cacao, coconut, papaya, mango, olive trees, and black pepper, this is a pathogen of great concern. The pathogen is found in various regions of the planet ranging from Africa, India, South America, and even the temperate regions of North America. It has been estimated that 10-20% of all cacao is lost due to Phytophthora Pod Rots (PPR) which includes P. palmivora. Due to P. palmivora’s dependence on moisture, the annual yield loss fluctuates and in some years losses have been as high as 75% in some regions. This impacts the cost of cacao, and thus the pathogen controls the cost and availability of products such as chocolate. In mangoes, the pathogen is known to kill young plants, specifically nursery plants. This impacts the long-term number of commercially available plants which could lead to potentially lower crop yields. In coconuts, the expected yield losses caused by P. palmivora have been up to 2.5% per month during the rainy season, this can impact coconut product manufacturing such as coconut oil. In the 1970s P. palmivora had such a severe impact on black pepper plants in Brazil that it was no longer commercially grown, and it is considered the most detrimental pathogen of black pepper. As previously stated impacts of P. palmivora commercially cause it to be a pathogen of significant importance.

Related Research Articles

<i>Phytophthora</i> Genus of single-celled organisms

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. The cell wall of Phytophthora is made up of cellulose. The genus was first described by Heinrich Anton de Bary in 1875. Approximately 210 species have been described, although 100–500 undiscovered Phytophthora species are estimated to exist.

<i>Phytophthora cinnamomi</i> Species of single-celled organism

Phytophthora cinnamomi, also known as cinnamon fungus, is a soil-borne water mould that produces an infection which causes a condition in plants variously called "dieback", "root rot", or, "ink disease".

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.

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.

<i>Phytophthora cactorum</i> Species of single-celled organism

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.

<i>Phytophthora medicaginis</i> Species of single-celled organism

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.

<i>Phytophthora erythroseptica</i> Species of single-celled organism

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.

<i>Phytophthora capsici</i> Species of single-celled organism

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.

Phytophthora fragariae is a fungus-like (oomycete) plant pathogen that causes red stele, otherwise known as Lanarkshire disease, in strawberries. Symptoms of red stele can include a red core in the roots, wilting of leaves, reduced flowering, stunting, and bitter fruit. The pathogen is spread via zoospores swimming through water present in the soil, released from sporangia.

Phytophthora megakarya is an oomycete plant pathogen that causes black pod disease in cocoa trees in west and central Africa. This pathogen can cause detrimental loss of yield in the economically important cocoa industry, worth approximately $70 billion annually. It can damage any part of the tree, causing total yield losses which can easily reach 20-25%. A mixture of chemical and cultural controls, as well as choosing resistant plant varieties, are often necessary to control this pathogen.

<i>Phytophthora plurivora</i> Species of single-celled organism

Phytophthora plurivora is a very aggressive soil-borne plant pathogen, with worldwide distribution and a wide variety of hosts.

Phytophthora quercina is a papillate homothallic soil-borne plant pathogen causing root rot of oak tree species in Europe. It is associated with necrotic fine roots.

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.

Phytophthora hydropathica is an oomycete plant pathogen that is found in aquatic environments such as irrigation and river water. The pathogen was previously classified as P. drechsleri Dre II before being categorized as its own distinct species. P. hydropathica has been primarily found in association with ornamental plant nurseries. The pathogen has been isolated throughout the Southern United States, as well as internationally in Mexico, Italy, and Spain.

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.

Cranberry Root Rot (CRR) is a disease in cranberries that can cause a decline in yield.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Phytophthora palmivora (E.J.Butler) E.J.Butler stdterms.in GBIF Secretariat (2017). GBIF Backbone Taxonomy. Checklist dataset https://doi.org/10.15468/39omei accessed via https://www.gbif.org/species/3203590 on 2018-06-25.
  2. ↑ Tucker, C.M. (1931) Taxonomy of the genus Phytophtora de Bary University of Missouri Agricultural Experiment Station Research Bulletin 153;
  3. ↑ Butler (October 2008). "October 08 Pathogen of the Month" (PDF). Australian Plant Pathology Society (APPS). (link: mn114-part2.pdf). Retrieved 15 November 2016.
  4. 1 2 3 4 Abd-Elsalam, Kamel; Mohamed, Heba (2022). Abd-Elsalam, Kamel A.; Mohamed, Heba I. (eds.). Cereal Diseases: Nanobiotechnological Approaches for Diagnosis and Management (1 ed.). Springer Science and Business Media LLC. pp. xii + 406 + 1b/willus. doi:10.1007/978-981-19-3120-8. ISBN   978-981-19-3119-2. S2CID   253100324. 978-981-19-3119-2. 978-981-19-3122-2. 978-981-19-3120-8.
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