‘Suicidal Hatch’ a potential management strategy for potato cyst nematodes

12 June 2020: It may be possible to manage potato cyst nematodes (PCN), currently a key threat to potato production in eastern Africa, by inducing ‘suicidal hatching’ of the pests using naturally occurring chemicals in crop roots.

These findings of a study by the International Centre of Insect Physiology and Ecology (icipe); International Institute of Tropical Agriculture (IITA); North Carolina State University, USA; and Kenyatta University, Kenya; have been published in Frontiers in Plant Science journal (paper link: https://bit.ly/30z440W).

Invasive and challenging

Nematodes are tiny microscopic worms, with some soil dwelling species infecting and adversely affecting most, if not all, cultivated crops. PCNs are invasive nematode pests that were first reported in Kenya in 2015, and have since been confirmed from other countries in eastern Africa. Studies by icipe and partners have shown that PCN is causing up to 80% yield loss in potato, one of the region’s most important crops.

“The management of PCN is particularly challenging due to the pest’s ability to survive in the soil as tiny protective cysts. These cysts can contain up to 600 eggs, but are able to remain dormant in the absence of a host plant for up to 20 years even. Once a field is infested with PCN, it is impossible to eradicate the pest. Therefore, a possible effective approach is to avoid the build-up and spread of the pest,” says Prof. Baldwyn Torto, Head, Behavioural and Chemical Ecology Unit, icipe.

Understanding and exploiting PCN signals

The recent studies by icipe and partners aimed to achieve this goal by exploring several known facts about PCN. First, is the fact that PCN eggs will hatch only in the presence of suitable host plants of the Solanaceae family, such as potato, tomato and African nightshade. Once hatched, the infective juvenile nematodes that emerge from the cyst seek host crop roots to invade and feed upon. The developing female nematodes swell and eventually become a new cyst full of eggs. A second truth is that PCN eggs hatch only once triggered by chemical signals produced by roots of the host plant.

The aim of the research was to identify these signals, and whether they can be exploited to induce hatch of PCN juveniles in the absence of host crops and thus lead to their eventual death; or rather the ‘suicidal hatch’ of the nematodes.

“We noted that most juvenile PCN that hatched in response to some chemical signals, known as steroidal glycoalkaloids (SGAs) and steroidal alkaloids (SAs), remained encysted. In other words, they did not leave the cyst to invade crop roots but remained encapsulated in the cyst,” noted Juliet Ochola (Kenya), who was involved in the research as part of her MSc studies, based at icipe and registered at Kenyatta University.

Prof. Danny Coyne, Soil Health Scientist, IITA, further explains that the SGAs and SAs could be used in synthentic forms to stimulate suicidal hatch of PCN in infested fields before farmers plant potatoes. Alternatively, plants that produce the chemicals but are not usually infected by PCN could be incorporated in a crop rotation system to stimulate PCN hatch, thereby reducing populations of the pest.

“Blends of the compounds obtained from crude material of such plants may be used to treat potato fields as organic soil amendments. This approach would be environmentally attractive and better than using nematicides, which can be hazardous, and due to their dependence on single compounds, are prone to pest resistance,” he notes.

From vision to impact

“As icipe celebrates its 50 years anniversary, this research is yet another illustration of how the Centre synergises resources, expertise and partnerships to contribute to the global knowledge hub, while building scientific capacity in Africa and addressing critical challenges facing the continent,” noted Dr Segenet Kelemu, icipe Director General & CEO. 

“As a young researcher, being involved in this study and working with a diverse team of mentors has been enormously rewarding. I have hugely expanded my skills in chemical ecology, alongside my passion to understand biological interactions in nature. It is also also really exciting to think that our findings can have a big impact on smallholder farmers who rely on potato cultivation, ” adds Juliet.

The importance of potatoes in eastern Africa has increased over the last 20 years, as a source of revenue and nutrition. Therefore, the likely outcome of the icipe-led study in reducing the devastating impact of PCN is significant. Even more so as the region, in tandem with the rest of the world, contemplates ways to reinforce food systems within the context of the ongoing COVID-19 pandemic.

Notes for Editors

Publication details:  

Ochola J, Cortada L, Ng’ang’a M, Hassanali A, Coyne D and Torto B (2020) Mediation of Potato–Potato Cyst Nematode, G. rostochiensis Interaction by Specific Root Exudate Compounds. Frontiers in Plant Science, 11:649. doi: 10.3389/fpls.2020.00649

Corresponding author: Baldwyn Torto; btorto@icipe.org

Funding: Financial support for this research was provided by North Carolina State University, USA; Root Tubers and Bananas Cluster of the CGIAR. icipe gratefully acknowledges the financial support of the following core donors: Swiss Agency for Development and Cooperation (SDC); Swedish International Development Cooperation Agency (Sida); UK Aid, from the government of the United Kingdom; the Ministry of Higher Education, Science and Technology, Kenya; and the Government of the Federal Democratic Republic of Ethiopia. The views expressed herein do not necessarily reflect those of these donors.

Research collaborators: Behavioural and Chemical Ecology Unit, International Centre of Insect Physiology and Ecology, Kenya; Department of Chemistry, Kenyatta University, Kenya; and International Institute of Tropical Agriculture.

The International Centre of Insect Physiology and Ecology (www.icipe.org): Our mission is to help alleviate poverty, ensure food security, and improve the overall health status of peoples of the tropics, by developing and disseminating management tools and strategies for harmful and useful arthropods, while preserving the natural resource base through research and capacity building.