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

Summary

Researchers studied a fungus called Diaporthe that causes soft rot disease in kiwifruit, which is an important crop. They found that the fungus produces special enzymes (pectinases) that help it break down the fruit’s protective cell walls, causing decay. By testing different temperatures, pH levels, and incubation times, they determined the best conditions to produce these harmful enzymes and confirmed they play a major role in disease development.

Background

Diaporthe Z1-1N is the primary causal agent of soft rot disease in kiwifruit, exhibiting higher pectinase activity than cellulase activity. Pectinases are pivotal enzymes in plant pathogenesis that facilitate fungal penetration through plant cell walls. Understanding the optimal conditions for pectinase production is essential for studying the pathogenic mechanisms of this fungus.

Objective

To evaluate the effects of incubation temperature, duration, and medium pH on the activities of two crucial pectinases (polygalacturonase and polymethylgalacturonase) produced by Diaporthe Z1-1N using single-factor and orthogonal experimental designs. Additionally, to assess the pathogenicity of purified pectinase extracts compared with fungal mycelium on kiwifruit.

Results

Optimal conditions for both pectinases occurred at pH 7.5 and 28°C, with PMG peaking on day 3 and PG on day 4. Under optimized orthogonal design conditions (28°C, pH 7.0, 2 days), PMG activity reached 11.228 U/mL with higher activity than PG (10.056 U/mL). Temperature was the most influential factor (R=1.14), followed by incubation duration (R=0.58) and pH (R=0.35). Purified pectinase extracts induced lesions at 50% the severity of fungal mycelium.

Conclusion

The study demonstrates that PMG and PG are significant virulence factors in Diaporthe Z1-1N pathogenicity on kiwifruit, with temperature being the most critical optimization parameter. The findings provide a foundation for further research on enzyme functions in soft rot disease development and may inform strategies for disease management in kiwifruit production.
  • Published in:PeerJ,
  • Study Type:Experimental/Optimization Study,
  • Source: 10.7717/peerj.19207; PMID: 40256738
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