JANITOR A. (2002): Growth of mycelia of phytopathogenic fungi after application of abscisic acid in in vitro conditions. Plant Protect. Sci., 38: 94-97.The effect of abscisic acid (ABA) on growth of mycelia of the phytopathogenic fungi Schizophyllum commune, Monilia laxa and Monilia fructigena in in vitro conditions was studied. All concentrations of ABA (from 10 -5 to 10 -9 M) stimulated mycelial growth of these fungi in Lilly-Barnet medium, when cultured for either 10 or 15 days. The results suggest that ABA secretion may be a factor of pathogenicity. Keywords: Schizophyllum commune; Monilia laxa; Monilia fructigena; mycelium growth; in vitro condition; abscisic acid 95Plant Protection Science -2002 Vol. 38, No. 3: 94-97 RESULTS AND DISCUSSIONOur study confirmed that ABA stimulates the growth of mycelium of the Schizophyllum commune and Monilia sp. isolates.Sch. commune was sensitive to all concentrations of ABA used. Higher concentrations of ABA (10 -5 and 10 -6 M) showed little stimulatory effect compared to the concentrations 10 -7 , 10 -8 and 10 -9 M, with 10 -8 M giving maximum stimulation. Fig. 1 shows the results after 10 and 15 d of culture.The two isolates of Monilia laxa gave almost the same response as Sch. commune to the concentrations of ABA (Fig. 2). Both fungi are known to secrete ABA into the culture medium JANITOR & VIZÁROVÁ 1994).The isolates of M. fructigena demonstrated even higher sensitivity to all tested concentrations of ABA (Fig. 3). Though the differences between the dry matter of mycelia of M. laxa and M. fructigena were small, they were significant. Similar results were reported by VASJUK & MUSATENKO (1998) with the phytopathogenic fungus Septoria tritici Roberge ex. Dem. Vol. 38, No. 3: 94-97 Plant Protection Science -2002 Our results agree with earlier literature that described the stimulatory effects of low ABA concentrations on fungal growth (e.g. MICHNIEWICZ et al. 1984MICHNIEWICZ et al. , 1986 STOPINSKA & MICHNIEWICZ 1988). It was also reported that ABA concentrations from 10 -5 to 10 -9 M stimulated the growth of mycelium of the soil micromycete Aspergillus niger Tiech. (JANITOR & VIZÁROVÁ 2000). We noted that all fungi that have been studied during the last years for the effect of ABA on mycelial growth, also secrete ABA into the culture medium.The data presented in the figures clearly show the positive and stimulatory influence of ABA on fungal growth, contributing to the general knowledge of this aspect. At the same time, it is known that ABA inhibits growth and development of higher plants, negatively influencing their metabolic processes (PROCHÁZKA et al. 1977).Thus, while the production of ABA by phytopathogenic fungi positively influences their own growth, the secretion of ABA into plants during pathogenesis is detrimental to the attacked plants. Both actions combined appear to constitute a factor in pathogenicity.

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