Experts claim that the dramatic increase in South Africa’s average winter temperature over the past 40 years has altered the susceptibility of apples to fungal disease. It seems that fungi are showing a much faster adaptation rate to changing temperatures than apples.
Apple orchards in the coastal regions of the Western Cape, such as Elgin, are affected to a greater extent by rising winter temperatures than those in the colder inland regions such as the Koue Bokkeveld.
Apple scab is caused by the fungus Venturia inaequalis, commonly known as Fusi. It is responsible for high economic losses to the apple export industry due to the blemishes and deformities it causes on the fruit.
In 2017, Dr Trevor Koopman of the Agricultural Research Council made an intriguing discovery using genetic fingerprinting of apple scab fungi during his studies in the Fruit and Postharvest Pathology Research Programme led by Dr Cheryl Lennox at Stellenbosch University.
Koopman found that the fungal populations in Elgin were distinctly different from those collected in the mountainous Koue Bokkeveld region. Such differences in genetic fingerprints point to a potential adaptation of the fungus to the new climatic conditions of higher winter temperatures.