Interactive physiological potential of Peyronellaea curtisii (=Phoma narcissi) strains for enzymatic attack and defence capabilities against phytoalexins

Abstract

Phytopathogenic fungi use a variety of strategies to infect hosts and have a diverse sensitivity to the natural defence mechanisms of the host plant, e.g. synthesis of phytoalexins. Many important pathogens of crops belong to the problematic genus Phoma, including species recently reallocated to Peyronellaea. The work presents: (1) molecular identification of five pathogenic strains of Peyronellaea (syn. Phoma) based on two loci, actin (ACT) and β-tubulin (TUB), and morphological observations; (2) differentiation of these strains based on their enzymatic activity; and (3) their effect on biosynthesis of phytoalexin in Hippeastrum scales. Phylogenetic analysis showed a close relationship between our strains and Peyronellaea curtisii (syn. Phoma narcissi) species. This was also supported by morpho-anatomical analysis although its results were less conclusive. Some phenotypic traits of the strains overlapped with characteristics of other Phoma s.l. species, allowing for misidentification based on morphology alone. Tested cellulolytic, pectolytic and amylolytic activities were strain specific. A high level of amylase activity was positively correlated with cellulase activity but negatively correlated with pectolytic activity. Moreover, some strains suppressed phytoalexin production in Hippeastrum scales and were resistant to various concentrations of phytoalexin added to the culture medium. Based on these results, we suggest that pathogenicity in P. curtisii strains is complex and that it may be associated with their interactive physiological potential for enzymatic attack and defence capabilities against phytoalexin.