ABSTRACT
The fungus Cylindrocladium spathiphylli causes collar and root rot in spathiphyllum. Fungi produce extracellular enzymes, most of which can be involved in pathogenicity. There are few studies that aim to prove the role of a certain enzyme in pathogenicity, especially for the pathosystem C. spathiphylli and spathiphyllum. Thus, the aim of the present study was to verify, under BOD conditions, the pathogenicity of different fungal isolates in spathiphyllum and to relate such pathogenicity to the in vitro production of the extracellular enzyme laccase. The pathogenicity assay was completely randomized with two normal isolates and three isolates altered by fungistasis, in six replicates. After inoculation, disease severity in spathiphyllum seedlings was evaluated at four different periods (until 10 days), using a score scale (1.0=health to 3.0=death of seedling). At 10 days, mean disease severity caused by the normal isolate MMBF 01/01 was similar to that caused by the altered isolates MMBF 01/01 – 9 D and LFEEI016 – 3 D, while the disease severity caused by the normal isolate LFEEI016 did not differ from that of control. The altered isolate MMBF 01/01 – 3 D showed maximum disease severity (average score 3.0) at seven days of evaluation, differing from the remaining isolates. As to the enzyme laccase, a completely randomized assay was designed with the same fungal isolates on Petri plate containing specific medium for laccase production, in six replicates. The area of the circular crown formed in the medium was measured. The largest mean area of the enzyme was produced by the altered isolate MMBF 01/01 – 3 D (2256.0 mm2), while the areas produced by the altered isolates LFEEI016 – 3 D and MMBF 01/01 – 9 D were equal to that produced by the normal isolate MMBF 01/01, and the smallest area of laccase was produced by the normal isolate LFEEI016 (747.2 mm2). In vitro production of the enzyme laccase was related to the disease severity caused by the isolates in the plant, which reinforces the need of further in vitro studies to prove the role of laccase in the pathogenicity of the fungus C. spathiphylli in spathiphyllum.
Keywords
Spathiphyllum; root and collar rot; aggressiveness; pathogenicity