Fungi and fungi-like Oomycetes isolated from affected leaves of rhododendron

The aim of the work is to identify fungi and fungi-like Oomycetes occurring on affected leaves of rhododendron Rhododendron L. Mycological analyses were carried out on 200 leaves collected from green areas of Kraków from May till September 2005. Isolated fungilike Oomycetes belonged to 67 taxa. The most frequently found fungi included: Alternaria alternata, Aspergillus niger, Botrytis cinerea, Coelophoma empetri, Nigrospora sphaerica, Pestalotia sydowiana, Phialophora cyclaminis, Phomopsis archeri, Septoria azalea and Sordaria fimicola. Among fungi-like organisms Phytophthora cinnamomi and P. citricola were isolated.

The aim of this work was to identify the organisms occurring on affected rhododendron leaves in green areas of Kraków.

MATERIAL AND METHODS
Leaves of rhododendron with the symptoms of discoloration, brown spots or ne-rhododendron with the symptoms of discoloration, brown spots or necroses were collected from the plants in the Botanical Garden of the Jagiellonian University, the Zoological Garden and town lawns in Kraków.200 leaves from 50 plants were collected for mycological analysis.The numbers of leaves taken from the top part (T), central part (C) and lower part (L) of the plant were approximately equal.The leaf samples were disinfected in 70% ethyl alcohol and 5 parts of each leaf from the area between ill and healthy tissue were put on Petri dishes with 2% PDA medium.The colonies of fungi and fungi-like Oomycetes �ere ide�tified u�i�g variou� media for ide�tificatio�: Guba (����)� Dom�ch et al. (����)� Sutto� (����)� Ho (1981), Ellis and Ellis (1987).

RESULTS
From the collected material 721 colonies of fungi, 19 colonies of fungi-like Oomycetes and 150 colonies of bacteria (not being the subject of this paper) were isolated.The isolated fungi and Oomycetes belonged to 67 taxa within 37 genera.
Among the species isolated from the leaves situated in the central part of the plants, the following were predominant: A. alternata, B. cinerea, C. empetri, C. gloeosporioides, E. purpurascens, N. sphaerica, P. sydowiana, S. fimicola and fungi belonging to genera: Aspergillus, Chaetomium, Cladosporium, Humicola and Penicillium.
From leaves situated in the lower parts of the plant, the following were isolated: Cylindrocarpon destructans, C. scoparium, Ph. archeri, Rhizoctonia solani, S. fimicola, Trichothecium roseum and fungi of genera: Acremonium, Fusarium, Mortierella and Phialophora.From the lower parts also Ph. cinnamomi and Ph.citricola were isolated.
From the leaves situated at the top part of the plant, numerous colonies of A. alternata, C. empetri, S. azalea, S. fimicola were isolated.Less frequent were: E. vaccinii, Mucor hiemalis, P. sydowiana, Pycnostysanus azaleae and fungi of genera Trichoderma and Phoma.
The frequency of species occurrence of fungi and fungi-like Oomycetes on leafblades was differentiated.The following species occurred at the highest frequency: A. alternata, S. fimicola, P. sydowiana, S. azalea and C. empetri.They were isolated (respectively) from 27, 11, 9, 8 and 7 leaves.Less frequently (on 5-6 leaves) occurred: Aspergillus niger, B. cinerea, Cladosporium macrocarpum, C. gloeosporioides, The remaining were isolated form 1-2 leaves (Tab.1).Rhododendron symptoms caused by fungi and fungi-like Oomycetes were varied.From chlorosis affected leaves with discoloration changes alongside the main veins, C. destructans, C. tenue, C. scoparium, and also three species of Fusarium were isolated.Fungus R. solani, causing the rhizoctoniosis in rhododendron, was isolated from the leaves with irregular brown-grey spots, surrounded by a large yellow area.B. cinerea, the cause of Botrytis petal blight, was isolated from rapidly dying leaves, with the symptoms of necrosis, such as large brown spots covered with dense grey mould.Fungus E. vaccinii, was isolated from deformed leaves with small reddish and brownish galls, typical of azalea leaf a�d flo�er gall.The cause of large oval necrotic �pot� �ith dark li�i�g� a�d vi�ible pic�idia �a� ide�tified a� Ph. archeri.
Other pathogens occurring in phyllosphere, such as C. gloeosporioides (causing rhododendron anthracnose), Gloeosporium rhododendri, Morenoina rhododendri, C. empetri and S. azalea (the reason for leaf scorch) caused round, oval or irregular necrotic spots of different shapes.A sign of C. gloeosporioides infection was grey spots, with visible rings and picnidia.In case of S. azalea, small oval, grey-brown spots with darker lining were seen.Necrotic spots caused by Ph. cyclaminis and P. richardsiae were small irregular with uneven edges.P. sydowiana was isolated from large light brown necrotic spots appearing on the edges and the tops of the leaves.
In this work P. sydowiana was frequently isolated.Łaba�o��ki et al. (2001) do not attribute necroses to this species.The role of P. sydowiana in causing necroses of heathers in nurseries and in permanent sites was described by Kowalik and Sa-heathers in nurseries and in permanent sites was described by Kowalik and Sagan (2005) as well as Kowalik and Wandzel (2005), while Kita and Mazurek (2003), in phyllosphere of azaleas and rhododendrons found quite numerously occurring: Pestalotia fibricola, P. rhododendrii and P. truncata.In the works by Kowalik and Muras (2007) fungus P. sydowiana together with A. alternata, occurred causing spots and necroses of rhododendron leaves and intensifying the process of leaf drop were isolated at large frequency.
While analysing the plant material, it was found out that, in addition to the above mentioned causes of discolorations, brown spots and necroses, the secondarily i�vadi�g fu�gi o� pathological leave� �ere ide�tified.They �ere the follo�i�g: A. alternata, S. fimicola, N. sphaerica, A. niger and the species of genera: Acremonium, Cladosporium, Humicola, Mortierella, Mucor, Penicillium, Phoma and Trichoderma.Accordi�g to �er�er a�d ��a��a (����) the�e fu�gi ca� i�te��ify pathogenic processes.Inhabiting small necrotic areas in a short time they rapidly inten-in a short time they rapidly intensify the process of necrosis.A large participation of fungi from genera: Alternaria, Cladosporium, Epicoccum and Phoma in the phyllosphere of rhododendrons is mentioned by Kita and Mazurek (2003).Their work indicates that these saprotrophs dominate in the structure of the populations of isolated fungi.The obtained results co�firm co��iderable participation of A. alternata, E. purpurascens, C. macrocarpum, C. sphaerospermum and many species of Phoma in the populations of fungi isolated from necrotic tissues of rhododendrons.
It can be concluded that a large biodiversity of fungi and fungi-like Oomycetes isolated from the affected rhododendron leaves in the green areas of Kraków caused different pathologic symptoms and decreased decorative value of the plants.

CONCLUSIONS
The most numerous fungi occurring in the rhododendron plantings in the green 1.
Phytophthora cinnamomi and Ph.citricola were isolated from the affected rhododendron leaves.The causes of discolorations, brown spots and necroses of the rhododen-, brown spots and necroses of the rhododen-spots and necroses of the rhododen-and necroses of the rhododen-and necroses of the rhododen-3.
rhizoctoniosis, anthracnose, leaf scorch, azalea leaf a�d flo�er gall were found.The effect was leaf drop and, in consequence decreased decorative value of the plants.