Potatoes have indeed been a staple food in many cultures for centuries, earning them the title of the “king of vegetables” worldwide. Their versatility allows them to be prepared in countless ways, from mashed and roasted to fried and baked, making them a favorite ingredient in a wide variety of dishes. Besides being nutrient-rich, whether as a side dish, a main course, or even a snack, potatoes have certainly earned their place as a beloved food choice for many people.

While peeling a potato in your kitchen, you may observe a dark purple or black discoloration on or beneath the peel. Sometimes, we simply opt to discard the discolored section and proceed to cook the rest.

But do we think what triggers this phenomenon? It’s none other than the blight disease affecting potatoes. This affliction remains a significant concern for potato farmers worldwide, as it can devastate acres of potato fields, resulting in major financial losses for businesses involved in potato cultivation.

It is a hemibiotrophic pathogen requiring living plant tissue to survive and complete its life cycle.

SAGROPIA prioritizes addressing potato blight, recognizing the need for sustainable solutions beyond chemical fertilizers. As part of this effort, Wageningen Research in the Netherlands, a key partner in the project, will evaluate bio fungicides in trials targeting early/late blight of potatoes. By reducing dependence on chemical treatments, SAGROPIA aims to promote ecologically sound agricultural practices, ensuring the production of healthy and safe potatoes while addressing broader environmental concerns associated with intensive farming.

This group of fungi is the most destructive of plant pathogens. Blight infects both potatoes and tomatoes. In potatoes, blight first attacks the foliage and when not managed on time, gradually passes into the tubers.

@Shutterstock

The historical famine and Blight

Irish Famine Memorial, Dublin, Ireland (image @Shutterstock)

Once upon a time, this black or purple coloration found in potatoes, now recognized as a fungal disease called blight, played a pivotal role in the Irish famine of 1845-49, devastating potato crops across Ireland. Blight hindered the proper growth of potato plants, which, for most of the Irish population at the time, constituted their primary food source, leaving them with scant alternatives for sustenance. Termed as the Great Hunger (An Gorta Mor in Irish), this famine resulted in a significant population decline of 2-3 million people, with many succumbing to illness or starvation as a direct consequence of the blight-induced potato crop failures.

Blight and Climate Change

In the context of climate change, it’s important to consider the impact on pathogen-host relationships in fungal infections like blight. Changes in climatic patterns can directly affect these relationships, particularly through alterations in habitat temperatures. As temperatures rise, the reproductive models and stress tolerances of both hosts and pathogens may be affected.

The thermal mismatch theory suggests that the fitness of hosts and pathogens often peaks at different temperatures, which could influence the dynamics of infection. Furthermore, pathogen infections involve various biological and biochemical processes, each regulated by enzymes with specific temperature preferences. Therefore, shifts in temperature due to climate change can potentially disrupt these processes, altering the spread and severity of bacterial blight and similar diseases.

Early blight is common and found widely in North America. This fungal disease in potatoes is caused by strains of Alternaria solani and A. alternata causing tissues to rot. Although this pathogen can most likely spread in any moderate to warm weather (15 °C to 27 °C), temperatures in-between 28 °C to 30°C are its optimum temperature range. These temperatures, together with moisture and relative humidity greater than 90%, can add to its speed in proliferation. Infection occurs when spores of the fungus encounter susceptible leaves and sufficient free moisture is present. Spore germination and infection are favored by warm weather and wet conditions from dew, rain, or sprinkler irrigation. Alternately, wet and dry periods with relatively dry, windy conditions favor spore dispersal and disease spread. Tubers can be infected as they are lifted through the soil at harvest. If sufficient moisture is present, spores germinate and infect the tubers.

Scorched leaf and infected tuber @Shutterstock

The causal pathogen Phytophthora infestans of Late blight is a winter eukaryotic microorganism that prefers moist and cold environments. Above 15°C, sporangia directly invade the host, but it takes a long time. The hyphae invade into the host body and spread fastest at 20~23°C, and the symptoms are the most obvious in winter. Therefore, early planted potatoes (for example in the Autumn season) generally escape the attack of late blight because of the relatively warmer climate. Under favorable climatic conditions, even one single tuber infected with the pathogen can be enough to create a severe epidemic situation.

Living with the Pathogen

Significant strides have been achieved in the management of blight since its infamous appearance in the 1800s. Improved agronomic practices, enhanced detection, and prediction systems, and—most importantly—the extensive use of effective chemical pesticides. Although present management strategies can successfully prevent catastrophic potato blight outbreaks, the environmental and economic costs associated with the overuse of these high-chemical pesticides are growing more unsustainable, due to changes in the global climate and rising consumer demand for organic food sources. Thus, it will be crucial to develop sustainable solutions to combat diseases like blight. These kinds of integrated and innovative strategies are essential to bringing new technological advances in pathogen research into a new era of effective integrated pest management plans for global sustainable potato farming.