Apple Trouble: New Fungal Threats in Northern Italy

In recent years, apple growers in Northern Italy have faced a new challenge. The usual suspects, fungi from the Acutatum complex, have been causing more trouble than ever before. These fungi are notorious for Apple Bitter Rot, a disease that has traditionally hit apples post-harvest. However, now it's becoming a big problem before harvest, affecting both apples and leaves. This is a double whammy because these fungi also cause Glomerella Leaf Spot, a nasty disease that damages leaves. To make matters worse, fungi from the Gloeosporioides complex, which were once rare in Europe, are now showing up more often. This shift has apple growers and scientists scrambling to figure out how to manage these diseases.

From 2021 to 2023, scientists collected samples from apple fruits and leaves in three regions: Emilia-Romagna, Veneto, and Trentino-Alto Adige. They found several types of fungi. One type, C. chrysophilum, was the most common, making up nearly half of the samples. C. fioriniae and C. siamense were also found in significant numbers. A few samples were identified as C. grossum and C. sojae. These fungi belong to different groups. C. chrysophilum, C. siamense, and C. grossum are part of the Gloeosporioides complex, while C. fioriniae is in the Acutatum complex, and C. sojae is in the Orchidearum complex. Researchers then tested how aggressive these fungi were on both wounded and unwounded Gala apple fruits and leaves. C. siamense turned out to be the most aggressive, closely followed by C. grossum. Surprisingly, C. sojae didn't cause any damage to fruits and only affected wounded leaves. This study sheds light on the diversity of these fungi in Italy and highlights the emergence of new species, C. siamense and C. sojae, which have never been reported in the country before. These findings could explain why disease patterns have been changing recently. It's a wake-up call for apple growers and scientists to adapt their strategies to tackle these new threats.

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