Elucidation of Twig Canker and Shoot Blight (TCSB) in Peach Caused by Diaporthe amygdali in the North of Italy in Emilia-Romagna

Summary

Peach trees in northern Italy are suffering from a disease called twig canker and shoot blight caused by a fungus called Diaporthe amygdali. This research identified and characterized this fungus from affected orchards, studying how it grows at different temperatures to better understand and control the disease. The fungus grows best around 23-24°C and can survive extreme heat above 50°C. These findings will help fruit growers develop better strategies to protect their peach crops.

Background

Prunus persica (peach) is a major fruit crop globally, with Spain and Italy as leading EU producers. Twig canker and shoot blight (TCSB) caused by Diaporthe amygdali has re-emerged as a significant disease in Italian peach orchards, causing substantial dieback of shoots, flowers, leaves, and branches. Despite its economic impact, comprehensive knowledge on this pathogen’s biological characteristics in Italian orchards remains limited.

Objective

This study aimed to characterize D. amygdali isolates from symptomatic peach trees in Emilia-Romagna, Italy through morphological and molecular analyses. The research assessed mycelial extension at different temperatures to identify optimal growth conditions and develop decision support systems for targeted disease control strategies.

Results

All 50 isolates were confirmed as D. amygdali through molecular and phylogenetic analyses. Three distinct morphotypes were identified. Isolate DA-1 showed significantly higher mycelial extension rates than DA-5 and DA-16. Optimal growth temperatures were centered around 23-24°C, with minimum thresholds ranging from 5-7°C and maximum at 40°C. Isolates showed differential thermal tolerance, with DA-16 surviving exposure to 54°C.

Conclusion

This study provides novel insights into D. amygdali characteristics on peach trees in Italy, confirming it as the predominant TCSB causal agent. The identification of previously unreported morphological characteristics and quantitative temperature-dependent mycelial extension data provides a foundation for developing targeted disease management strategies and decision support systems for Italian peach production.
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