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Remarks (public):For a complete description including images see 
Remarks (internal):Although the fungus grows on several agar media it has been claimed hot water extracts of strawberry petioles greatly stimulate growth and perithecial production (45, 2020) and more isolates produced perithecia on Leonian's agar than on potato dextrose or corn meal agar (51, 2694). It has also been claimed that perithecial initiation is determined by a favourable balance between stimulatory substances (strawberry petiole or vitamins) and other mycelial constituents (45, 2019). In synthetic media more than one compound e.g. a casein hydrolysate, low concentrations of L-valine, or certain groups of amino acids have been reported to promote perithecial production (45, 2020). Optimum temperature for growth is 25°C with a minimum and maximum of 5°C and 35°C, and the optimum pH for growth varies between 4,5-6,1 (Bolay, 1972). In California, USA, foliar disease caused by G. comari is considered to be unimportant because infection of strawberry is restricted to the crown of plants (Wilhelm, 1961) but in Canada (Bolton, 1954), Western Spain (52, 3776) and UK (Shipton, 1967) severe losses have been reported in nursery and commercial fields. Most strawberry cvs. have been claimed to be susceptible to infection by G. comari; in Spain the disease has been prevalent on petioles and flower stalks of the cv. Tioga (52, 3776). In a survey carried out in UK cv. Red Gaundet has been reported to be most susceptible whilst Cambridge Favourite and Regina were severely affected and Cambridge Prizewinner was less susceptible (Shipton, 1967). In Spain chemical treatments failed to give satisfactory control against G. comari (53, 2263) but it has been reported in Germany good control can be obtained by spraying with dichlofluanid (Euparen) 2-3 weeks before flowering and again 10-14 days later. In the field it may be possible sometimes to confuse the pycnidial state of G. comari on strawberry with Phomopsis obscurans (Ellis & Everh.) Sutton (= Dendrophoma obscurans (Ellis & Everh.) Anderson; CMI Descriptions 227) but the two fungi can be readily distingrushed by the nature of the fruiting structures, conidiophores and conidial morphology.
Description type:Non-original description 
Description:Gnomonia comari Karsten, Bidrag till Kannedom af Finlands Natur och Folk 23: 122-123, 1873.
Gnomonia herbicola A. L. Smith, Transactions of the British Mycological Society 3: 221, 1910.
Gnomonia fragariae Klebahn f.sp. fructicola Arnaud, Traite de Pathologie Vegetale Encyclopedie Mycologique Tome 1, Vol. 2, part 4: 1558-1562, 1931.
Gnornonia fructicola (Arnaud) Fall, Canadian Journal of Botany 29: 309, 1951.
Conidial state: Zythia fragariae Laibach, Arbeiten aus der Kaiserlichen Biologischen Anstaltfur Land- und Forstwirtschaft 6: 79-80, 1908.
For full discussion on taxonomy see Bolay, 1972.
Colony on oat, potato dextrose and potato carrot agar colourless to brick red, reverse colourless to tawny. Mycelium hyaline to dull yellow; aerial mycelium sparse. Perithecia abundant, solitary, dark brown to black, up to 1,2mm long, base rounded and up to 500 µm diam., neck up to 1 mm long. Asci cylindrical to subclavate, substipitate, 20-30 x 5-7 µm, 8-spored, ascus wall thin, unitunicate, evanescent. Ascospores biseriate, hyaline, fusiform to ellipsoid, straight or slightly curved, medianly or unequally 1-septate, slightly constricted at the septum, (9-) 10-12 x 2-2,5 µm. Conidiomata pycnidial, yellowish-brown, sometimes with the floor of the pycnidial cavity convoluted, ostiolate, up to 400 µm diam; pycnidial wall composed of several layers of cells, the outer layers yellowish-brown, the inner layers hyaline. Conidiophores hyaline, simple, cylindrical, short, septate, occasionally branched, arising from the innermost layer of cells lining the pycnidial cavity and the incomplete columns or pillars of tissue, 10-15 (-25) µm long. Conidiogerious cells hyaline, cylindrical to lageniform, enteroblastic, phialidic. Conidia hyaline, short cylindrical, rounded at both ends, guttulate, 5-7 x 1,5-2 µm. On the host plant the bulbous bases of the perithecia remain immersed with their long necks emerging to the outside through the host tissue. Pycnidial conidiomata at first remain immersed but later become erumpent, lenticular, 170-200 µm wide.
Hosts: Fragaria vesca, F. chilonensis var. ananassa and Fragaria cvs. Also on Agrimonia, Alchemilla, Comarum, Epilobium, Geum, Potentilla and Sanguisorba.
Disease: Leaf blotch, dry necrosis of sepal tips, fruit rot and dying of strawberry plants. Also rotting of strawberry runners in cold storage (50, 189). Although the disease is economically unimportant in Switzerland, Bolay (1972) claims in Germany, UK and North America yield losses can reach 70%.
Geographical distribution: Africa (Zimbabwe); Asia (Israel); Australasia & Oceania (New Zealand); Europe (Denmark, Finland, France, Germany, Greece, Netherlands, Poland, Rumania, Spain, Sweden, Switzerland, UK, Yugoslavia); North America (Canada, British Columbia, Newfoundland, Nova Scotia, Ontario, Quebec; USA, California, Maine, Michigan, New Hampshire).
Physiological specialization: None reported. According to Bolay (1972) G. comari occurs on several members of Rosaceae and the fungus is homothallic. Several reports indicate that most isolates of G. comari grow readily on synthetic media (33, 737; 43, 2525; 51, 2694; 52, 3775) and those isolates derived from Fragaria are partially deficient in thiamine (45, 2020). So far 4 groups of isolates have been recognized on the basis of perithecia formation on various media (51, 2694).
Transmission: By conidia and ascospores disseminated by water splash during humid conditions (Bolton, 1954). The fungus overwinters on leaves left in the field and in nature perithecia occur on overwintered leaves in early spring. Infection starts early in the season (Bolton, 1954; 51, 2693) by the entry of the fungus through stomata and wounds (33, 737; Bolay, 1972). Once the fungus has entered the leaf it penetrates the parenchyma cells and progessses towards the vascular bundles and enters the vessels producing profuse mycelium and subsequently numerous pycnidia (Bolton, 1954). In Western Spain under laboratory conditions pycnidia have been produced on infected plants in 4-5 days and perithecia in 8-10 days (52, 3776). In Canada pycnidia were observed in the cortex of petioles 4 weeks after inoculation and leaves with pycnidia kept in a moist chamber were found to develop perithecia in 4-6 days (Bolton, 1954). Perithecia developed in this way took 10-12 days to mature.
Literature: Barr, Mycologia Memoir of the New York Botanical Garden No. 7: 1-232, 1978 (taxonomy); Bolay, Bericht der Schweizerischen Botanischen Gesellschaft 81: 398-48, 1972; Bolton, Canadian Journal of Botany 32: 172- 181, 1954; Dennis, British Ascomycetes, J. Cramer, Vaduz, 1978; Shipton, Plant Pathology 16: 123-125, 1967; Wilhelm, Circular. California Agricultural Extension Service No. 494: 21, 1961.
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