Cellulolytic Actitivity of Penicillium digitatum and P. italicum Related to Fungal Growth and to Pathogenesis in Citrus Fruits

Abstract

Cultural conditions under which Penicillium digitatum and P. italicum develop were an important factor in determining the extent of their cellulolytic activity. At pH 5.5–7.5 of the culture medium, Cx‐cellulase activity was correlated with mycelial dry weight. However, at pH 4.5 and more so at pH 3.5, activity was markedly reduced while fungal growth was not affected. Cx‐cellulases of both species were not induced by the presence of carboxymethyl cellulose as a carbon source and were defined as constituent enzymes. Cellulase activity of the two Penicillia on different carbon sources was detected prior to the initiation of sporulation. A sporeless mutant of P. digitatum exhibited cellulolytic activity similar to that of the normal strain, suggesting no role for sporulation in the Cx‐cellulase synthesis. Cx‐cellulase activity in Valencia oranges started during the early stages of pathogenesis, before the appearance of disease symptoms. Correlation between the cellulase activity and the severity of the disease symptoms was apparent during the first three days after inoculation. At the end of the incubation period both fungi almost reached their maximum enzymatic activity, whereas the disease index continued to rise gradually until total fruit rot was achieved. A possible role of Cx‐cellulases of the two Penicillia in the early stages of pathogenesis was suggested.

Cell wall-degrading enzymes of Didymella bryoniae in relation to fungal growth and virulence in cantaloupe fruit

“…A few reports have shown that Cx was related to virulence (Barkei-Golan and Karadavid 1991; Gough et al 1988; Le-Cam et al 1994). In this study, the Cx activity of D. bryoniae did not correlate with the virulence of the fungal isolates grown in the CMC shake culture, but the fungal Cx activity in fruit tissue shake culture and in decayed cantaloupe fruit was correlated with fungal virulence.…”

“…The role of hemicellulases and cellulases in pathogenicity and virulence of plant pathogens are largely undetermined (Novo et al 2006). However, cellulolytic activity of Penicillium digitatum and P. italicum was reported to correlate with fungal growth and pathogenesis in citrus fruit (Barkai-Golan and Karadavid 1991). Recently, Vu et al (2012) determined that cellulases were virulence factors of Magnaporthe oryzae .…”

Estudio de los factores de patogenicidad/virulencia de Penicillium digitatum sobre frutos cítricos.

“…Para reducir el potencial impacto negativo de los tratamientos antifúngicos en la calidad de los frutos cítricos, el curado y los tratamientos de agua caliente han sido combinados con envases individuales de plástico para la fruta (Rodov et al 2000), radiaciones ionizantes a bajas dosis (Spalding et al 1987;Barkai-Golan et al 1969), tratamientos UV (D'hallewin et al 1994) o breves choques de CO 2 (Palou et al 2008). También han sido ampliamente estudiadas las soluciones acuosas calientes de cualquiera de los fungicidas convencionales (Schirra y Mulas 1995; con químicos alternativos de baja toxicidad, tales como carbonato sódico y bicarbonato sódico (Palou et al 2001), sorbato potásico (Smilanick et al 2008), benzoato sódico y molibdato amónico , etanol, dióxido de azufre (Smilanick et al 1995), de forma que aumentan significativamente su efectividad frente a las podredumbres de Penicillium y otras enfermedades postcosecha de cítricos.…”