Abstract
Sooty canker, caused by <i>Neoscytalidium dimidiatum</i> (Penz.) Crous and Slippers, Synon. = <i>Nattrassia mangiferae</i> (Syd. and P. Syd.) B. Sutton and Dyko, on the inoculated thin bark saplings (12-24 months old) of <i>Eucalyptus camaldulensis</i>, <i>Olea europaea</i>, and <i>Populus nigra</i> was monitored under greenhouse conditions every 2 days until the 8<sup>th</sup> day, and it was repeated 18, 28, 58 days after inoculation. Predisposition to stem cankers depended on the duration of warm temperature and abundance of fungal inoculum. The infected bark was discolored and revealed a black mass of fungal arthroconidia, particularly on the most susceptible plants of eucalyptus and poplar. The cankers extended to 18.53 mm and 16.11 mm on eucalyptus and poplar, respectively, after 58 days compared to 10 mm for non-inoculated saplings (wounding sites) of control treatment. The effect of temperature conditions before and after inoculation with <i>N. dimidiatum</i> on canker development on the same plants was studied in a growth chamber with two temperature regimes, very hot 40<sup>o</sup>C and hot 32<sup>o</sup>C. Among pre-inoculation regimes, very hot and hot temperatures were the most conductive to infection of eucalyptus saplings compared to other hosts, which showed a non-significant dependence between pre- and post-inoculation. Thus, heat stress of 32 and 40<sup>o</sup>C on the most susceptible host, eucalyptus, sustained the progress of cankers to 17.20-17.56 mm after 3 days and 18.08-18.06 mm after 5 days of inoculation.
Highlights
In the hottest months (June, July, and August) during 2001-2010, sudden limbs wilt or sooty canker invaded thousands of thin or smooth bark trees and ornamentals such as mulberry, ash, walnut, fig, sycamore, apple, apricot, and poplar in Iraq (Hassan et al 2009).The fungus was identified as Nattrassia mangiferae
The mycelial synanamorph was described as Scytalidium dimidiatum (Penz.) B
Necrosis caused by Neoscytalidium might be limited within wounded tissues of such tolerant hosts as olive, since cankers developed to a length of only 11.40 mm, compared with 13.60 mm and 14.30 mm on poplar and eucalyptus, respectively (Fig. 2)
Summary
In the hottest months (June, July, and August) during 2001-2010, sudden limbs wilt or sooty canker invaded thousands of thin or smooth bark trees and ornamentals such as mulberry, ash, walnut, fig, sycamore, apple, apricot, and poplar in Iraq (Hassan et al 2009).The fungus was identified as Nattrassia mangiferae The fungus was identified as Nattrassia mangiferae Crouse et al (2006) employed DNA sequence data of the 28S rDNA to resolve apparent lineages within the Botryosphaeriaceae, they recognized 10 lineages within the Botryosphaeriaceae, and the new genus is proposed to accommodate this fungus called Neoscytalidium (Penz.) Crous & Slippers, and the species called N. dimidiatum (Penz.) Crous & Slippers. The colonies grew rapidly, filling the Petri plate within 4-7 days, becoming olivaceous grey to black and overlaid with aerial strands of grayish black mycelia, hyphae fragmented to form cylindrical or barrel-shaped bark brown non-septate or one septate arthroconidia, pycnidial conidia developed one or two septa and a brown median band, with the upper and lower cells being subhyline with tapered ends (Sigler et al 1997)
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