Potato blight makes history

The potato blight is caused by the oomycete Phytophthora infestans. Oomycetes (sometimes referred to as pseudo-fungi) are more closely related to brown algae and diatoms than to the true fungi. However, similar to the true fungi, they consist of a mesh of cellular threads, the mycelium. If tubers are infected in the soil, the oomycete begins to grow inside the tuber. The interior of the afflicted tuber shows a brownish discolouration and the tubers become inedible – both unappetising and harmful to human health, due to the presence of toxins.

Once the potato germinates, P. infestans grows into the sprouting plant. Brown areas and dark spots appear along the edges of the leaves and soon spread across the entire leaf surface.

The underside of the leaves on the infected plant is covered with a white layer of fungal hyphae, the so-called “potato mildew”. Here, the sporangia develop, which release spores during wet conditions. This can lead to a rapid spread of the oomycete, particularly during moist weather. While wet conditions damage the potato plants, they favour P. infestans, which requires moisture and moderate temperatures for an effective propagation. During dry weather, there is no risk of infection.

P. infestans made history when the organism that causes the potato blight destroyed large parts of the European potato harvest between 1845 and 1852. Ireland was hit the hardest. The potato constituted the country’s primary food source and was usually planted in monocultures. Therefore, the potato blight that wiped out almost the entire harvest in 1846 and 1847 had catastrophic consequences. The number of people who died of starvation is estimated at around 1 million.

An additional million Irish left their country and emigrated to Canada, Australia and the USA. As a result, the population of Ireland shrank by about 3 million people between 1841 and 1871.

A herbarium is a collection of dried and pressed plants. The Herbarium Senckenbergianum in Frankfurt/Main comprises approx.1.2 million of such herbarium voucher specimens – the oldest dating back to the 17th century.

One of the eleven historical herbarium sheets used in the study came from the collection at Kew Gardens, dated 1846, and contains the leaf of a potato plant infected with P. infestans.

The historical and current samples were compared using modern decoding methods for the genetic material and DNA analysis. The comparison of certain sections of the DNA makes it possible to determine relationships between different organisms. In this process, mathematical algorithms are used to estimate at what time the individual Phytophthora lineages became genetically separated from each other – even beyond the 150-year period in which the samples originated.

The topics of the exhibitions at the Senckenberg Naturmuseum in Frankfurt/Main (left), which is part of the Senckenberg Gesellschaft, range from the fauna and flora of long bygone times across geology and the development of the Earth to the diversity of modern organisms. In the process, the transformation of habitats over millions of years is clearly illustrated. With more than 38 million objects, the Senckenberg Gesellschaft houses one of the world’s most extensive natural history collections. Most of the objects are not on display; they are used solely for research purposes.

The dinosaur skeletons are the highlights of the exhibition: Iguanodon (left), original skeleton of a Diplodocus longus (right). This is the only skeleton of its kind on display outside the USA.

The varied exhibition areas of the Senckenberg Naturmuseum in Frankfurt display countless exhibits. Many of these represent extremely rare or even unique specimens, including a mounted Anaconda, which is among the world’s largest snakes. Shown here is the enormous prey (in this case a Capybara) this snake is able to devour in one piece.

In the next few years, the museum’s exhibition space will be expanded from 6,000 to 10,000 square metres. A new, globally unique concept provides for four major exhibition areas: Human, Earth, Cosmos and Future.