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Optimization of cultural conditions for pectinase production by Diaporthe isolate Z1-1N and its pathogenicity on kiwifruit

Summary

Researchers studied how a fungus called Diaporthe causes soft rot in kiwifruit by producing special enzymes called pectinases that break down the fruit’s cell walls. They found the best conditions for growing these enzymes in the lab: a temperature of 28°C, neutral pH around 7.5, and 2-3 days of growth. When they extracted these pure enzymes and put them on fresh kiwifruit, the enzymes caused damage equivalent to about half the damage caused by the living fungus itself, proving these enzymes are important for disease development.

Background

Diaporthe Z1-1N is the primary causal agent of soft rot disease in kiwifruit, exhibiting higher pectinase activity compared to cellulase activity. Pectinases are pivotal enzymes in plant pathogenesis and are among the initial enzymes synthesized by fungal pathogens during plant cell wall colonization.

Objective

To evaluate the effects of incubation temperature (18-38°C), duration (1-7 days), and medium pH (4.0-9.0) on the activities of two crucial pectinases: polygalacturonase (PG) and polymethylgalacturonase (PMG) from Diaporthe Z1-1N. To establish optimal culture conditions for enzyme production and assess the pathogenicity of purified pectinase extracts on kiwifruit.

Results

Optimal conditions for PMG production were pH 7.5, 28°C temperature, and 3 days incubation; PG peaked on the fourth day under the same conditions. Through orthogonal design optimization, PMG activity reached 11.228 U/mL at 28°C, pH 7.5, and 2 days incubation. Temperature was the most influential factor on PMG activity, followed by incubation duration and pH. Purified pectinase extracts induced lesions equivalent to 50% of those caused by fungal mycelium.

Conclusion

PMG and PG are key virulence factors in Diaporthe Z1-1N pathogenicity on kiwifruit, with PMG exhibiting higher activity than PG under optimized conditions. The purified pectinase extracts demonstrated significant pathogenic potential, confirming the role of these enzymes in soft rot disease development. These findings provide a foundation for future research into the functions and regulation of these pectinases in fungal-host interactions.
  • Published in:PeerJ,
  • Study Type:Experimental Study,
  • Source: 10.7717/peerj.19207, PMID: 40256738
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