THE PATHOLOGICAL STUDY OF PLANE TREES DECLINE IN SHIRAZ CITY

Plane trees (Platanus orientalis) decline is prevalent in Shiraz and other parts of the country. From 50 plane trees with decline symptoms, forty one yielded several fungi such as Cytospera (42.85%), Alternaria (18.9%), Aspergillus (12.7%), Nattrassia mangiferae (3.22%), Penicillium (3.05%), Rhizopus (0.7%), Helminthosporium (0.24%), Chaetomium (0.2%), Coniothyrium (0.2%) and Ulocladium (0.07%). The fungi were inoculated to detached stem of plane tree. Only N. mangiferae and few isolates of Cytospora were pathogenic. From 41 isolates of Cytospora recovered, only 8 isolates were mildly pathogenic to detached but not to intact plane tree. From ten isolates of Cytospora inoculated to detached stem of Acer pseudoplatanus, Platanus orientalis, Magnolia grandiflora, Morus alba, Citrus aurantium, Malus communis, Juglans regia, Cercis siliquastrum, Fraxinus excelser and Pinus sp. only 1 isolate was pathogenic on M. alba and 5 to C. siliquastrum. None of the 40 Cytospora isolates caused infection of stem the above plants under natural conditions. On the basis of morphological characteristics the fungus was identified as Cytospora theryana. There was no significant differences among soil samples collected around declining and healthy plane tree in Shiraz in respect to soil, EC, pH and soil texture. It is concluded that plane tree decline in Shiraz city is as the result of various environmental and nutritional stresses which predisposed trees to various opportunistic fungi.