Histological Change in Cucumber Tissue and Cellulase Activity of Plectosphaerella melonis Strain 502

Abstract

In the last ten years, many countries around the world recorded a new disease of the Cucurbitaceae, the agent of which was P. melonis. The ability of P. melonis 502 to form intracellular mycelium in the epidermal and parenchymal tissues of roots was shown. Leading tissues (xylem and phloem) did not colonize, which indicates the impossibility of plant vessel clogging and shows the fungus’s biochemical effects on plants, which causes the process of pathogenesis. P. melonis 502 is able to develop in a wide range of pH values, while the pH-optimum is 8.5. P. melonis 502 is able to adjust the pH of the medium to the optimal value—8.5. We also showed that cellulase enzyme synthesis depends on pH. We studied the exo-, endo- and β-glucasidase activity of P. melonis 502 and found that the highest activity of cellulase enzymes was on a medium whose pH was 8.5. In the process, the total cellulolytic activity was 0.326 U mL−1, exoglucanase activity—0.539 U mL−1, endoglucanase activity—0.950 U mL−1 and β-glucosidase activity—0.795 U mL−1.

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“…It allows the fungus to penetrate inside cells and create the intracellular mycelium. Mainly, the epiderma and parenchymatous tissues of the root are damaged, and their ruination occurs at the effect of cellulase enzymes (Patyka et al, 2022). We have also shown the growthregulating activity of P. melonis 502 and its ability to synthesize a phytohormone, ethylene .…”

“…Previously we have shown that P. melonis 502 is capable of active synthesis of cellulase enzymes (exo-, endocellulases and β-glucosidases), which trigger the degradation of the cellular wall of the plant (Patyka et al, 2022). It allows the fungus to penetrate inside cells and create the intracellular mycelium.…”

“…3). Generally, the incubation period of the disease and the susceptibility of plants may vary depending on the environmental conditions, especially temperature and pH, which affect not only the growth and development of a microorganism, but also its synthesis of biologically active substances (Коріlov et al, 2021;Patyka et al, 2022).…”

“…In Ukraine, this disease was fi rst registered in 2012 in cucumber plants, cultivated in the covered soil, where P. melonis strain 502 was isolated (Kopilov et al, 2021). We have already studied the capability of the cultural liquid of P. melonis 502 to regulate the growth of plants depending on the test culture and to synthesize the phytohormone ethylene in vitro (Tsekhmister et al, 2021); we have also investigated the histotrophic localization of the pathogen and its ability to synthesize cellulase enzymes depending on environmental conditions (Patyka et al, 2022), and in this study, our work aimed to demonstrate the phylogenetic relations between P. melonis strain 502 and the isolates from other countries and to study the sensitivity of different varieties of Cucumis sativus L.…”