Discovering the Cause of Pineapple Leaf Spot Disease

Jim Crocker
24th January, 2024

Image Source: Natural Science News, 2024

In 2017, pineapple farmers in Alor Pongsu, a region in the northwest of Peninsular Malaysia, noticed troubling brown spots on the leaves of their Josapine variety pineapples. As these spots spread, they combined to form large lesions that ended up killing the plants. Over the next few years, this disease was seen affecting 10-15% of pineapples in other areas throughout Malaysia as well. Researchers sought to pinpoint the exact cause of this disease. To do so, they collected 20 samples of the affected leaves from Alor Pongsu and ran a series of tests. The process included cutting the leaf tissues, sterilizing them, and then placing them on a growth medium known as Potato Dextrose Agar. After allowing the potential pathogens to grow, scientists used a technique to isolate and identify the fungal culprit based on how it looked and its genetic markers. All identified culprits showed consistent physical traits. In their initial growth stage, the fungi had white, fluffy mycelia—thread-like structures making up the body of the fungus. These mycelia then darkened with age. Upon closer inspection of these fungi after two weeks, it was noted that they had branched structures typically brown in color, with a type of fungal spore called arthroconidia, which were clear and either round or oval in shape. Their findings pointed towards a specific fungus—Neoscytalidium. By analyzing the genetic material of this fungus, they confirmed that it was a type called Neoscytalidium dimidiatum, which had an exact match with a known reference sequence. The information was added to a global database for future reference. To confirm that this fungus was indeed the villain behind the leaf spots, researchers conducted an experiment. They purposely infected healthy Josapine pineapple plants with the fungus and observed if similar symptoms developed. Indeed, the plants showed the same disease signs as those in the field, whereas the control plants, which were treated with a harmless substance, remained healthy. Furthermore, the fungus could be re-captured from these newly infected plants, confirming that it was the same as identified earlier. This fungus isn't new to Malaysia; it's known to infect other types of plants, causing various diseases. However, this is the first time it has been identified as the reason for the leaf spots on Josapine pineapples in Malaysia. This discovery is a starting point for developing ways to manage this plant disease and reduce the losses in pineapple crops.

Fruits Plant Science Agriculture

References

Main Study

1) First Report of Leaf Spot of Pineapple (Ananas comosus (L.) Merr Caused by Neoscytalidium dimidiatum in Malaysia.

Published 22nd January, 2024

https://doi.org/10.1094/PDIS-09-23-1796-PDN

References

Main Study

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