Didymella lycopersici

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Didymella lycopersici
Systematics
Class : Dothideomycetes
Subclass : Pleosporomycetidae
Order : Pleosporales
Family : Didymellaceae
Genre : Didymella
Type : Didymella lycopersici
Scientific name
Didymella lycopersici
Klebahn

Didymella lycopersici ( synonym : Boeremia lycopersici ) is a kind from the order of pleosporales in the department of hose mushrooms (Ascomycota). It is the causative agent of Didymella stem rot (also called tomato stem rot ), especially in tomatoes , but also in potatoes, aubergines and peppers.

features

The pseudothecia grow to 120–200 µm in culture and up to 300 µm in size on the host, are round, light brown with a wart-like opening (ostiolum). The bitunicate asci are cylindrical to club-like, short-stalked or sessile with eight spores and reach a size of 50–70 × 8–9 µm in culture or 70–95 × 6–10 µm on the host. The hyaline spores have oil droplets, are irregularly double-rowed, elliptical and grow to 12-15 × 5 µm in culture and 16-18 × 5.5 µm on the host. The pseudo paraphyses are filiform, also hyaline and septate. The dark brown pycnidia appear on the stem, leaves or fruits are solitary or gregarious. They are first sunk in the tissue or then break out and reach a diameter of 140 to 200 µm in culture or 180–250 µm on the host. Their cell walls consist of pseudoparenchymatic cells , the outermost layer of which is slightly thicker. The conidia are hyaline, elliptical to ovate, with no or at most one septum and are 6–10 × 2–3 µm in size.

Morphology and life cycle

The fungus overwinters in plant remains by means of conidia. Airborne ascospores or infected seeds seem to be less common. Spores are mainly formed on older infected areas. With renewed moisture, gray to pink mycelium grows and spores form again. These are spread with water splashes and mechanically via tools and clothing. The spores can spread over 100 to 75 cm up and down the plant by spraying water. The fungus can also be spread via recirculating irrigation systems and lead to infections. Didymella is favored by high humidity, light and temperatures at 15 ° C. Optimal growth takes place at 15-20 ° C. Above 20 ° C the fungus only develops better under very favorable conditions. The minor fruit form occurs most, while the main fruit form, the perithecia, almost never contributes to the spread. The spread from the ground is stronger than that through the seeds. The spores can stay on the seed for a maximum of 9 months.

Symptoms

The whole plant of tomatoes can be infested. D. lycopersici occurs mostly outdoors and only occasionally in the greenhouse. Usually the plant is attacked in the lower area and from the root neck upwards. Usually, the stem is first colonized by the formation of lesions. The lesions are brown to dark brown. The bark tissue sinks in and in a later stage black dots (fruiting bodies), the pycnidia, form . If the stalk is heavily infested, the flow of sap is interrupted and the plant dies above the infested site. This also destroys the tissue under the bark. The stem becomes soft and, under moist conditions, a pink tissue is formed and an aqueous spore mass emerges. If the infestation is a little weaker, the plant only wilts, whereby the fruits come to emergency ripe. Infested areas higher up on the plant in particular are caused by water splashes with spores. Leaves and fruits can also be attacked. However, the fruits are almost only attacked outdoors. Infestation can occur anywhere there, but usually begins on the calyx and grows rapidly. The growth shows up with concentric rings, which at first look watery and oily and later have sunk in blackish. Pycnidia also form in these places. If the fruit is completely infected, it is called mummification. The infestation on the leaf looks similar to that of Alternaria . The stain, however, turns light brown to gray with pycnidia similar to Phoma lingam in cabbage plants. Later on, the affected area can fall out like a shotgun . Sometimes the whole sheet is destroyed. Infestation from the root neck down is also known, but the plant continues to grow and the older leaves show signs of wilting or yellowing. The disease is less common in sandy locations. However, the penetration of the pests is promoted by injuries to the plant. The roots are very rarely attacked.

distribution

Didymella lycopersici is widespread. In Canada it is occasionally found in the British Columbia and Nova Scotia area. Didymella stem rot is quite common on tomatoes in Europe. It is also found on potatoes and eggplant. Likewise on plants and seeds of peppers.

Similar diseases

The disease can be confused with stem rot caused by gray rot ( Botrytis cinerea ) or late blight ( Phytophthora infestans ) or dry spot disease ( Alternaria solani ). The formation of pycnidia are characteristic of Didymella lycopersici , as they can be seen with a magnifying glass with 5 to 10 times magnification. The very rare root attack is also an indication of the disease. B. cinerea forms lawns of spores.

history

In 1921 Klebahn first described perithecia of Didymella lycopersici and named the fungus. It was not until 1944 that Hickman succeeded in doing this and was thus able to confirm the find. In 2005, Didymella stem rot is one of the three most important fungal diseases in the cultivation of tomatoes in the foil house in Estonia.

Forms and synonyms

Didymella lycopersici belongs to the pleomorphic organisms, ie it forms a main and a secondary fruit form. The anamorphic (secondary crop form) is called Phoma lycopersici . The following synonyms for Phoma lycopersici have been described: Diplodina lycopersici , Phoma ferrarisii , Ascochyta lycopersici , Sphaeronaema lycopersici , Diplodina lycopersicola , Ascochyta socia .

swell

Mycobank: Didymella lycopersici

Individual evidence

  1. ↑ a b c d e G. Crüger, GF Backhaus, M. Hommes, S. Smolka and H.-J. Vetten: Plant protection in vegetable cultivation , 4th edition, ISBN 3-8001-3191-9 , 2002, pp. 209-210.
  2. ^ DE Fischer: Internal Infection of Tomato Seed by Didymella lycopersici Kleb. In: Nature No. 174, 1954, pp. 656-657
  3. ↑ RB Maude: Seed transmission of Didymella stem-rot of tomatoes , in: Annals of Applied Biology . Vol. 50, Issue 1, 2008, pp. 105-111
  4. ↑ a b c d e f J. Dalchow: in: Gemüse , No. 2, Ulmer Verlag, 1997, p. 144.
  5. ^ A b c d C. Chupp and AF Sherf: Vegetable Diseases and Their Control , 1960, The Roland Press Company, pp. 562-563
  6. ^ J. Fagg and JT Fletcher: Studies of the epidemiology and control of tomato stem rot caused by Didymella lycopersici , in: Plant Pathology , Vol. 36, Issue 3, 2007, pp. 361-366.
  7. ↑ WP Staunton and TP Cormican: The Effects of the pathogen and Fungicides on Tomatoes in a hydroponic system . Acta Hort. No. 98, 1980, pp. 293-298.
  8. ↑ G. Bedlan: Vegetable diseases . Österreichischer Agrarverlag, 3rd edition, ISBN 3-7040-1565-2 , 1999, pp. 208-209.
  9. ↑ VA Martinson and NG Hogenboom: Screening young tomato seedlings for resistance to Didymella foot and stemrot , in: Euphytica , Vol. 17/2, ISSN  0014-2336 , 1968, pp. 173-182.
  10. ^ A b FAO Staff: Protected Cultivation in the Mediterranean Climate - 6.2.1.1 Tomato . Publisher: Food & Agriculture Org., 1990, ISBN 9-251027196 , pp. 191-204.
  11. ↑ C.-M. Messiaen, D. Blancard, F. Rouxel and R. Lafon: les maladies des plantes maraîchères , INRA Paris, 3rd edition, ISBN 2-7380-0286-2 , 1991, pp. 151-153.
  12. ↑ a b c W.R. Jarvis and CD McKeen: Tomato diseases , in: Agriculture Canada Publication 1479 / E , 1991
  13. ↑ Anonymous: Culture notes tomato . Enza Zaden Germany GmbH, 2004.
  14. ↑ mycobank
  15. ↑ RD Khulbe, AP Dhyani, MC Sati: Seed-borne Didymella lycopersici and Diaporthe phaseolorum: their location in seed, transmission and pathogenic importance in red pepper and bell pepper , in: Indian Phytopathology Vol. 44 No. 4, ISSN  0367-973X , 1991, pp. 480-486.
  16. ↑ H. Klebahn, Plant Diseases No. 30, 1921, p. 30
  17. ^ CJ Hickman: The Perithecial Stage of Didymella Lycopersici . in: Nature No. 154, 1944, pp. 708-708.
  18. ↑ I. Bender, K. and M. Annamaa Raudseping: Conservation of tomato genetic resources in Estonia , in: ECPGR Report of a Vegetables Network - meeting 2nd . Biodiversity International, ISBN 92-9043-792-8 , 2007, pp. 142-145.
  19. ^ G. Morgan-Jones and K.Burch: Studies in the genus Phoma. XI: Concerning Phoma lycopersici, the anamorph of Didymella lycopersici, causal organism of stem canker and fruit rot of tomato . in: Mycotaxon . Vol. 32, ISSN  0093-4666 , 1988, pp. 133-140.
  20. ↑ GH Boerema, J. de Gruyter, ME Noordeloos, MEC Hamers: Phoma identification manual: differentiation of specific and infra-specific taxa in culture . ISBN 0-85199-743-0 , 2004, p. 273.
  21. ↑ DF Farr and AY Rossman, Fungal Databases , Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved on July 19, 2009, USDA ARS Fungal Database ( Memento of the original from July 14, 2007 on WebCite ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / nt.ars-grin.gov

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