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Cultures of the anamorph on potato sucrose agar (pH 6.5) are pale beige with sparse white mycelium;purple discoloration later develops, accompanied by dark bluish-black, discrete stromata, some of which represent ascomatal initials. Microconidia unicellular, allantoid, curved, 5-10 x 2.5-3 µm. Macroconidia fusoid, falcate, 2-3 septate, 20-25 x 4-5 µm. Chlamydospores oval to globose, smooth or roughened, 10-15 x 8-10 µm.
Ascomata perithecioid, violaceous, embedded, single or in groups, in dark purple stromata;globose with a flattened base, 200-400 x 180-300 µm. Asci cylindrical, thin-walled, shortly pedicellate, 90-110 x 7-9.5 µm with 8 monostichous ascospores. Ascospores hyaline to straw-coloured, fusoid, 1-3 septate, finely roughened, 12-14.5 x 4.5-6 µm (Booth and Waterston, 1964).

Related invasive species

  • Gibberella xylarioides

Related Farm Practice

  • Wood
  • Groups

Related location

  • Nigeria
  • Ethiopia
Has Cabi datasheet ID
25166
Symptons

Fraselle (1950) described the disease symptoms fully on C. robusta in the Belgian Congo (formally Zaire and now Democratic Republic of Congo). First symptoms were described as generalized chlorosis of the leaves which became flaccid and curled. Leaves dry up, turn brown and very fragile, and abscise. The crowns of the dead trees are completely defoliated. The branches may turn black-brown or blackish, and dry up. The bark on the trunk is hypertrophied and has numerous vertical or spiral cracks which reveal blue-black streaks in the wood under the bark. In the roots, the black rot becomes moist. Infection may be general or partial. Van der Graaff and Peters (1978), describing the disease in C. arabica in Ethiopia, observed that dieback may start unilaterally and extend to the whole tree.
Internally, in the diseased wood, the main tracheids are heavily infected by mycelium. At the limit of spread, the tracheids alone are affected but where the infection is long established, the mycelium is found in the fibres surrounding the vessels and medullary rays (Fraselle, 1950). Wood parenchyma is rarely attacked but primary xylem and pith may be attacked. Tyloses develop and a yellow gum is observed (Fraselle, 1950). Such occlusion of the vessels leads to the characteristic wilting and desiccation of the foliage. Mycelium is rarely present in the bark, reaching only the cortical medullary rays but fungal reproductive structures (fruiting bodies) can sometime be observed on the outside of the bark at the base of infected trees.
Further details of symptoms can be seen in various chapters and plates in Flood (2009).

Hosts

Fusarium xylarioides (teleomorph = G. xylarioides) has been reported to be pathogenic to cotton seedlings of IAC 20 cultivar under laboratory conditions;less so under glasshouse conditions (Pizzinatto and Menten, 1991). It has also been isolated from rotting tomatoes in Nigeria (Onesirosan and Fatunla, 1976) but this may be a misidentification.

Oss tagged
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