6.59
COMMUNITIES OF RHIZOSPHERE FUNGI FROM CHINESE ASTER [CALLISTEPHUS CHINENSIS (L.) NEES] PLANTS OF CULTIVARS RESISTANT AND SUSCEPTIBLE TO FUSARIUM WILT
COMMUNITIES OF RHIZOSPHERE FUNGI FROM CHINESE ASTER [CALLISTEPHUS CHINENSIS (L.) NEES] PLANTS OF CULTIVARS RESISTANT AND SUSCEPTIBLE TO FUSARIUM WILT M MANKA and M KACPRZAK Department of Forest Pathology, University of Agriculture, ul. Wojska Poiskiego 71 c, 60-625 Poznah, Poland Background and objectives Chinese aster [Callistephus chinensis (L.) Nees.] cultivars differ a great deal in resistance to a severe wilt causing agent Fusarium oxysporum f.sp. callistephi (Beach) Snyd. et Hans. In susceptible cultivars the pathogen may considrably reduce yield or even devastate the whole plantation while resistant ones are not affected. Since F. Oxysporum is a soil-borne pathogen, which attacks roots reaching them through rhizosphere, it is interesting if the microbial relations in aster rhizosphere may be involved into the resistance phenomenon. Relations between saprophytic rhizosphere fungi and the pathogen are of particular interest. Materials and methods In late Summer 1997 at a horticultural farm in Wloclawek, central Poland (mud-muck soil, pH 4.5), resistant 'Perla' asters were symptomiess while susceptible 'Janina' plants were 40% affected and displayed wilting and necrosis. In September rhizosphere soil fungi communities were isolated both from healthy 'Peria' asters and from healthy and wilting 'Janina' plants. The isolation was performed with the Warcup soil plate method modified by Johnson and K Mahka [1]. The pathogen was obtained from stem base of 'Janina' plants showing symptoms of wilting and was tested for pathogenicity to asters in a greenhouse infection experiment, with positive result. Fungi building up the rhizosphere communities were tested for their effect on F. oxysporum f.sp. callistephi growth, according to the biotic series method [2]. Results and conclusions All the three communities of rhizosphere fungi (one from diseased and two from symptomiess asters) were rather poor in fungal species (ca 15 species each). They differed in their qualitative structure (the species building up the community) and the total number of isolates (= quantitative structure). The community from affected 'Janina' asters had 139 isolates, the one from symptomless 'Janina' asters consisted of 152 isolates and the community from symptomiess 'Perfa' plants of 209 isolates. Species most antagonistic to the pathogen (Trichoderma viride, T. Polysporum, Penicillium jensenii) were represented most frequently in the latter community, comming from the resistant cultivar. It seems that more numerous communities of fungi occur in rhizosphere of healthy asters. The greater share of antagonistic species in the fungal community may also have contributed to the actual better health status of the investigated 'Perla' plants. References 1. Johnson LF, Mahka K, 1961. Soil Science 92, 79-83. 2. Mahka K, Mahka M, 1992. IOBC/WPRS Bulletin 1992/XV/1, pp.73-75.