Taphrina Deformans
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''Taphrina deformans'' is a fungus and
plant pathogen Plant diseases are diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomycetes, bacteria, viruses, viroids, virus-like orga ...
, and a causal agent of
peach The peach (''Prunus persica'') is a deciduous tree first domesticated and Agriculture, cultivated in China. It bears edible juicy fruits with various characteristics, most called peaches and the glossy-skinned, non-fuzzy varieties called necta ...
leaf curl Peach leaf curl is a plant disease characterized by distortion and coloration of leaves and is caused by the fungus '' Taphrina deformans'', which infects peach, nectarine, and almond trees. ''T. deformans'' is found in the United States, Europe ...
. Peach trees infected with ''T. deformans'' will experience leaf puckering and distortion, acquiring a characteristic downward and inward curl. Leaves will also undergo chlorosis, turning a pale green or yellow, and later show a red or purple tint. Fruit can either drop prematurely or show surface distortions. Severe infection can also produce lesions on the flowers. The host tree will experience defoliation if the leaves are badly diseased. If a seedling is severely infected, it may die. Almond trees display similar symptoms.


Life cycle

''Taphrina deformans'' infects species of the genus ''
Prunus ''Prunus'' is a genus of flowering plant, flowering trees and shrubs from the family (biology), family Rosaceae. The genus includes plums, cherries, peaches, nectarines, apricots and almonds (collectively Drupe, stonefruit). The genus has a cosm ...
'' (including ''P. amygdalus'' (
almond The almond (''Prunus amygdalus'', Synonym (taxonomy)#Botany, syn. ''Prunus dulcis'') is a species of tree from the genus ''Prunus''. Along with the peach, it is classified in the subgenus ''Amygdalus'', distinguished from the other subgenera ...
) and ''P. persica'' (
peach The peach (''Prunus persica'') is a deciduous tree first domesticated and Agriculture, cultivated in China. It bears edible juicy fruits with various characteristics, most called peaches and the glossy-skinned, non-fuzzy varieties called necta ...
)). It is best known as the causative agent of
peach The peach (''Prunus persica'') is a deciduous tree first domesticated and Agriculture, cultivated in China. It bears edible juicy fruits with various characteristics, most called peaches and the glossy-skinned, non-fuzzy varieties called necta ...
leaf curl Peach leaf curl is a plant disease characterized by distortion and coloration of leaves and is caused by the fungus '' Taphrina deformans'', which infects peach, nectarine, and almond trees. ''T. deformans'' is found in the United States, Europe ...
in peaches and nectarines. It has been observed that this fungus also infects the fruits of some South American trees like ''
Ocotea puberula ''Ocotea puberula'' is a species of evergreen tree in the plant genus ''Ocotea'' of the family Lauraceae. It is found in Argentina, Brazil, French Guiana, Guyana, Mexico, Peru, and Suriname Suriname, officially the Republic of Suriname, is ...
'', '' Nectandra megapotamica'' and other
Lauraceae Lauraceae, or the laurels, is a plant Family (biology), family that includes the bay laurel, true laurel and its closest relatives. This family comprises about 2850 known species in about 45 genus (biology), genera worldwide. They are dicotyled ...
species. An additional form has been identified which infects
apricot An apricot (, ) is a fruit, or the tree that bears the fruit, of several species in the genus ''Prunus''. Usually an apricot is from the species '' P. armeniaca'', but the fruits of the other species in ''Prunus'' sect. ''Armeniaca'' are also ...
s. Some researchers posit that these forms are separate varieties altogether, which is supported by recent genetic evidence based on hybridization. Furthermore, almond strains of ''T. deformans'' seem to be unable to induce peach leaf curl on peach trees, and vice versa. Infected leaves develop a whitish bloom as the infection progresses. This bloom consists of asci that break through the
cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...
of the leaf by way of lysis.Bassi M, Conti GG, & Barbieri N. (1984). “Cell wall degradation by ''Taphrina deformans'' in host leaf cells.” ''Mycopathologia'' 88 (2-3) 115–125 One ascus contains eight
ascospore In fungi, an ascospore is the sexual spore formed inside an ascus—the sac-like cell that defines the division Ascomycota, the largest and most diverse Division (botany), division of fungi. After two parental cell nucleus, nuclei fuse, the ascu ...
s, which are ejected in early summer and moved by rain and wind. This fungus is believed to survive the winter by staying on the surface of the new host plant, such as on bark or buds. In the spring, new buds are infected by the conidia as the leaves emerge from the buds. The disease does not occur every year, as it requires a minimum of 3mm of rainfall followed by at least 12 days during which the developing conidia remain damp and at temperatures below 19 °C.Smith, S.E. What is Peach Leaf Curl? 2009. WiseGEEK. 14 Apr 2009 The fungus has higher infection rates following cooler, damper winters. ''Taphrina deformans'' hyphae growing in intercellular spaces
secrete Secretion is the movement of material from one point to another, such as a secreted chemical substance from a cell or gland. In contrast, excretion is the removal of certain substances or waste products from a cell or organism. The classical mec ...
polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long-chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wat ...
-degrading
enzymes An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as pro ...
, such as
cellulase Cellulase (; systematic name 4-β-D-glucan 4-glucanohydrolase) is any of several enzymes produced chiefly by fungi, bacteria, and protozoans that catalyze cellulolysis, the decomposition of cellulose and of some related polysaccharides: : Endo ...
, causing partial dissolution of the host
cell wall A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, ...
. This process also results in changes in the
plasma membrane The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extr ...
. ''T. deformans'' also produces the
auxin Auxins (plural of auxin ) are a class of plant hormones (or plant-growth regulators) with some morphogen-like characteristics. Auxins play a cardinal role in coordination of many growth and behavioral processes in plant life cycles and are essent ...
indole-3-acetic acid Indole-3-acetic acid (IAA, 3-IAA) is the most common naturally occurring plant hormone of the auxin class. It is the best known of the auxins, and has been the subject of extensive studies by plant physiologists. IAA is a derivative of indole, con ...
from L-tryptophan via indole-3-pyruvic acid and indole-3-acetaldehyde. This process is thought to be responsible for the hyperplastic effect of the infection.Yamada Y, Tsukamoto H, Shiraishi T, Nomura T, & Oku H. (1990). “Detection of Indoleacetic Acid Biosynthesis in Some Species of ''Taphrina'' Causing Hyperplastic Diseases in Plants” ''Annals of the Phytopathological Society of Japan''. 56 532–540


Peach leaf curl management

Because infection depends on a wet environment, appropriate irrigation of crops can help control pathogen dispersal. Although some sources also suggest thinning fruit to control the spread of disease, sanitation and culturing practices alone are insufficient to manage the pathogen. Fungicide is preferred; chlorothalonil and ziram are favored, and copper is an organic option. Fungicide application requires the correct timing and complete coverage of the crop. It is recommended that growers spray fungicides after leaf-fall, or after 90% senescence of leaves. In wetter climates, where multiple sprays may be necessary, spraying is recommended in the late fall and in late winter or early spring. Post-infection spraying of fungicide is inadequate to control the disease. Although most commercial cultivars are susceptible, there are several genotypes of ''Prunus persica'' that have been identified as resistant to infection by ''T. deformans''. These resistant genotypes appear to use molecular and biochemical mechanisms to manage the spread and development of the disease. For example, chlorogenic acid, which is known to have antifungal activity in vitro, is present in resistant strains but not susceptible strains. The chloroplasts are also activated as a site of defense signaling. Additionally, upregulation of the pattern of accumulation of isochorismate synthase indicates increased salicylic acid production. The activation of salicylic acid-dependent pathways suggests a mechanism to achieve systemic acquired resistance.


Importance

Peach leaf curl is present wherever peaches or nectarines are grown. The economic impact of the disease varies regionally, as pathogen spread and symptom severity depends on environmental factors. In the United States, $2.5 to 3 million dollars are lost because of peach leaf curl. Sixty to ninety percent of peach shoots in Italy can be infected by ''T. deformans.'' Although peach leaf curl is mostly manageable with fungicide spraying in dry climates, improper timing or incomplete coverage of the crop can result in control failure. Wetter climates which require multiple applications of fungicide will be more susceptible to human error. Additionally, unexpected winter warming can allow the pathogen to establish itself within buds before the late winter or early spring application of fungicide. Without fungicides, or through control failure, the disease can result in total yield loss, along with the stunting and death of shoots. Yield loss can result from tree defoliation, leading to decreased photosynthesis, and from infection of fruit, which decreases marketability.


''Taphrina deformans'' genome

''Taphrina deformans'' genome has been sequenced.Cisse, O. H., J. M. Almeida, A. Fonseca, A. A. Kumar, J. Salojarvi, K. Overmyer, P. M. Hauser and M. Pagni (2013). “Genome sequencing of the plant pathogen ''Taphrina deformans'', the causal agent of peach leaf curl." MBio 4(3) e00055-00013. The genome carries characteristic genes that are important for the plant infection process.


References


External links

* ''Taphrina deformans'' at Fungal Database

{{Taxonbar, from=Q2022500 Taphrinomycetes Fungi described in 1857 Fungal tree pathogens and diseases Stone fruit tree diseases Taxa named by Miles Joseph Berkeley Fungus species