Search on : Taxa descriptions

 


   
Literature:
 
Remarks (public):For a complete description including images see www.cababstractsplus.org/dfb 
Remarks (internal):Host penetration is probably stomatal (5, 459). More infection occurs at 16°C and 20°C than at 12°C and 24°C and the most rapid development of lesions is at 20°C. Most viable ascospores are formed at 16-20°C and mature perithecia do not develop on lesions unless the RH approaches saturation for at least 4 days. Growth in vitro is best at 20°C. The fungus is homothallic (25, 591). Penetration of the seedcoat occurs but it is not clear how important seed-borne spread is in the epidemiology of ringspot. Seed treatment with hot water (45°C for 20 min.) followed by thiram has been recommended (29, 341). Cultural control measures should be taken, clean healthy seedbeds and destruction of diseased tissue, particularly where crops are being grown for seed. Seedbeds should be isolated and rotation may be desirable. High volume sprays of maneb, mancozeb and dichlone were the best of 19 fungicides tested in Australia (50, 340). In USA benomyl gave almost complete control and chlorthalonil gave 90% control (49, 2218). Benomyl was also effective in New Zealand where June-July planting resulted in severe infection in contrast to earlier planting (52, 2406). No resistance was found in 40 cvs. of Brussels sprout (Brassica oleracea var. gemmifera; 37, 689).  
Description type:Non-original description 
Description:Mycosphaerella brassicicola (Duby) Lindau, Die Naturlichen Pflanzenfamilien, Leipzig 1: 424 (Fete) 1897.
= Sphaeria brassicicola Duby, Botanicon Gallicum 2: 712, 1830 (as brassicaecola).
= Spaerella brassicicola Cesati & de Notaris, 1863 (as brassicaecola).
= Mycosphaerella brwsicicola (Duby) Oudem., (March) 1897(as brassicaecola).
= Dothidea brassicae Desm., 1842.
= Sphaeria brassicicola Berk. & Broome, in Berkeley, 1860 (as brassicaecola).
Conidial state: Asteromella brassicae (Chev.) Boerema & van Kest., Persoonia 3: 18, 1964.
= Asteroma brassicae Chev., Flore generale des Enviorons de Paris 1: 449, 1826.
= Phyllosticta brassicicola McAlpine, 1901 (as brassicaecola).
= Phyllosticta brassicicola Grove, 1914.
For further synonyms see Boerema & van Kesteren, 1964.
Pseudothecia mostly on leaves but sometimes on stems and seed pods, globose, dark brown, with apical papillate ostioles,100 x 130 µm diam. Asci bitunicate, 8-spored, 30-45 x 12-18 µm. Ascospores irregularly biseriate, hyaline, cylindrical, 18-23 x 3-5 µm, rounded at the ends and not constricted at the septum.'Pycnidia' (spermagonia) solitary or gregarious, globose, dark brown, with papillate ostioles, 100-200 µm diam.; wall pseudoparenchymatic composed of several layers of cells. 'Conidia' (spermatial cells) hyaline, cylindrical, 3-5 x 1 µm.
Hosts: On Brassica spp.
Disease: Ringspot of Brassica spp.; the symptoms are most conspicuous on the outer leaves. The small necrotic spots enlarge to an average 0,5-1 (-2) cm diam.; the spots are generally circular with light brown or grey centres, a definite edge is bounded by a narrow water-soaked area and a chlorotic zone; where the lesions are numerous the whole leaf becomes yellowish and shows curled, cracked and ragged edges. Within the lesion the perithecia (hypophyllous at first, later amphigenous) form in a typically zonate manner; they may be extremely numerous and the lesion appears black. Rectangular or oval lesions are caused on the midribs, stems and siliqua (5, 459).
Geographical distribution: Widespread (CMI Map 189, ed. 3, 1969) but generally restricted to cool, moist regions; there are few records from Africa (Ethiopia, Ghana, Kenya, Morocco, South Africa, Uganda).
Physiological specialization: None reported.
Transmission: Air-borne ascospores but no specific studies reported. The pycnidia contain spermatia which are not infective (25, 591; 41, 112).
Literature: Nelson & Pound, Phytopathology 49: 633-640, 1959 (epidemiology); Dring, Transactions of the British Mycological Society 44: 253-264, 1961 (taxonomy & morphology); Boerema & van Kesteren, Persoonia 3: 17- 28, 1964 (nomenclature).


 
Taxon name: