Search on : Taxa descriptions

 


   
Literature:
 
Remarks (public):For a complete description including images see www.cababstractsplus.org/dfb 
Remarks (internal):Evidence has been produced to show that by regulating the nitrogen supply in the soil susceptible apple trees can become more resistant (45, 826). A programme of preventive spraying is recommended, three copper sprays being found effective in Britain (45, 1093), but a four spray programme is recommended for New Zealand (44, 3400). Good results have been obtained with mercury preparations alone or mixed with copper oxychloride (45, 2891). Bordeaux is widely used but was found to be ineffective in California (44, 1153)
 
Description type:Non-original description 
Description:Nectria galligena Bres., in Strasser, Verh. K.K. Zool. Bot. Ges. Wien. 51: 413, 1901.
= Fusarium heteronemum Berk. & Broome, 1865.
= Cylindrocarpon heteronemum (Berk. & Broome) Wollenw., 1928.
= Cylindrocarpon mali (Allesch.) Wollenw., 1928.
Perithecia gregarious on surface or edge of cankers, ovate to globose, bright red, becoming darker and warted with age, 250-350 µm diam., with a slightly convex and darker ostiolar disk. Asci clavate, 75-95 x 12-15 µm. Ascospores oval, ellipsoid or spindle-shaped and slightly constricted at the central septum, smooth to verrucose, hyaline, 14-22 x 6-9 µm. Lortie (43, 1565) found freshly isolated ascospores of Nectria galligena produced mature perithecia on powdered oat, wheat grains and powdered birch bark media with 1% agar after 8 weeks if kept in daylight with sealed petri dish lids, suggesting that light and a high moisture content are necessary for perithecial formation. Single ascospores or conidia isolated on potato dextrose agar form a colony 6 cm diam. after 14 days, aerial mycelium white, floccose to felted with faint yellow to yellowish-brown discoloration; from below agar becoming yellowish-brown and finally deep reddish-brown. Microconidia cylindrical with rounded ends, non-septate, 4-8 x 2-3 µm. Macroconidia develop from short cylindrical phialides, 12-16 x 2-2,5 µm, borne on multibranched conidiophores; those formed in culture resemble theones found on the host and are cylindrical, straight or curved with rounded ends, as follows:
1-septate 10-28 x 4-5 µm
2-septate 22-30 x 4-6 µm
3-septate 36-50 x 4-6 µm
4 or more septate 45-65 x 4-7 µm
In some isolates macroconidia are predominantly 1-2-septate and 17-28 x 4-5 µm. This may be a strain difference or a result of 'Abkultur' from growth on artificial media.
Culture filtrates show pectolytic activity (42: 495). ?-indoleacetic acid is secreted by N. galligena and is believed to be the cause of canker formation (32: 196). Small quantities of this substance stimulate growth in culture (30: 166) but higher concentrations inhibit growth (38: 464). The presence of other fungi or the addition of anti-auxinic metabolises such as pyruvic, citric or malic acids will counteract the effect of ?-indoleacetic acid.
Hosts: On apple (Malus) and pear (Pyrus). It has also been recorded on a large number of other hosts including: Acer, Betula, Carpinus, Carya, Fagus, Fraxinus, Juglans, Magnolia, Populus, Prunus, Quercus, Salix and Sorbus.
Disease: Canker, crotch canker (40: 115), crown dieback, storage rot or late storage rot of fruits. Nectria eye-rot of fruit on tree.
Geographical distribution: Distribution appears to coincide with the major apple and pear growing areas with the exception of Australia and its probable elimination from Tasmania. (CMI Map 38, Ed. 2, 1963).
Physiological specialization: Spore morphology appears to be related to some extent to the host (42: 494). Isolates from Salix can infect apple and pear (28: 93). Two varieties are reported from Chile (31: 373) which differ in their conidial states.
Transmission: Conidia spread by rain drops (42: 494; 45, 2689). A high R.H. is essential for ascospore discharge (40: 55; 42: 494), which occurs mainly in spring and autumn. Infection is chiefly by natural wounds, leaf scars (45, 2891), occasionally from the point of attachment of the fruits (42: 691) or from pruning wounds (43, 3250). Early discharge of the ascospores (in temperate regions) increases leaf scar infection and infection in northern temperate regions is most frequent between bud-burst (mid April) and shoot formation (late May) (42: 131).

 
Taxon name: