Halloween is almost here, and many of us will celebrate this autumn festival by carving a jack-o’-lantern pumpkin. But as you light a candle to place inside, spare a thought for the future of this versatile crop and its cousins.
Pumpkin and its relatives, like many other important crops, are threatened by climate change, declining interest in growing them and a loss of genetic diversity as farmers plant fewer varieties and wild relatives disappear. Urgent action is needed to protect the diversity that remains.
As part of the Crop Trust’s mission to safeguard crop diversity in perpetuity, key crops have been chosen for the development of comprehensive strategies to guide and coordinate global efforts for their conservation.
The multi-year effort to develop new strategies and update existing ones is funded by the German Federal Ministry of Food and Agriculture (BMEL).
Cucurbits, formally known as the Cucurbitaceae, are the plant family that includes pumpkins and its many tasty relatives, such as cucumber, squash, chayote and watermelon. The new Global Crop Conservation Strategy for Cucurbitaceae provides a road map for the coordinated conservation of this important and widely beloved plant family.
A Recipe for a Global Conservation Strategy
Authored by a group of experts at the Crop Trust and The World Vegetable Center (WorldVeg), as well as independent consultants, the new strategy is built upon an in-depth review of the existing scientific literature on cucurbits, the results of an online survey and recommendations from stakeholder deliberations.
Using these sources, the experts gathered information on important crops in the cucurbits family to learn their origins, where they are most plentiful, where their wild relatives are, how they are used and how they are being bred. They also looked at genebanks around the world to see which cucurbits are being safeguarded and which still need to be collected and conserved.
The Missing Cucurbits
In earlier times, crop biodiversity was preserved solely through the diverse range of varieties in farmers’ fields and of their wild relatives outside them. These are still important sources of cucurbit diversity, especially in the areas where the crops were first domesticated.
Over the last century, genebanks have begun to collect cucurbit diversity as it rapidly disappears from both wild and cultivated fields.
However, the strategy reveals that major genebanks have gaps in their cucurbit collections, both in the number of samples they hold and in the representation of species and varieties that have adapted to specific places and environments during the long history of cultivation. Why have these gaps arisen?
“Gaps in collections can be caused by many factors,” says Peter Giovannini, Global Crop Conservation Strategies Project Coordinator at the Crop Trust and a co-author of the cucurbits strategy. “Access to certain sites for collecting may be difficult. Some regions and countries do not have the resources to collect adequately, as it can be expensive and require a lot of coordination. And some collections may have been lost—that is, seeds have died—again, because of resource constraints.”
An important goal of the conservation strategy is to identify these gaps in genebank collections and prioritize filling them, so that the full range of diversity is captured and made available to future generations.
Filling in the Gaps
Maarten van Zonneveld, Genebank Manager at WorldVeg and co-author of the strategy, explains, “There are two types of diversity: the diversity among crops and that within each crop. Diversity among crops provides dietary diversity—think of the different nutrients found in squash, melons and so on. In contrast, diversity within a crop allows it to adapt to different environments or changes over time. The diversity within a crop is also what allows breeders to create new varieties that can succeed under hotter or dryer conditions.”
Consequently, the priority for cucurbit conservation is to collect additional species and varieties as soon as possible, with a focus on those from underrepresented areas, particularly those that tolerate heat, drought and poor soil quality, and those with resistance to pests and diseases.
According to the strategy, specific wild cucurbits should be targeted for collection, especially in centers of diversity, such as Mexico. Other regions with unique cucurbit biodiversity include Myanmar, Bangladesh, and China. Plants from all these regions are potential sources of genes for useful traits.
Fighting Conservation Challenges Together
A global network of genebanks harboring the widest biodiversity is essential for the future breeding of cucurbits. A continuing challenge for genebanks is to accurately document and safeguard these materials.
Careful storage is an important component of preservation. “Some species, such as bitter gourd, do not store well under standard genebank conditions,” adds Andreas Ebert, plant genetic resources consultant and co-author of the strategy. “We are only just starting to understand the optimal conditions for the long-term storage of this major food crop. This is one reason it is crucial for genebanks to document and share information about the specific storage conditions required by some crops.”
Indeed, seed viability is a major challenge for the long-term storage of many cucurbits. Seed longevity differs among species and varieties and is affected by storage conditions, including temperature, oxygen levels and humidity. Rigorous testing is needed to identify the best conditions for seed storage.
Seedborne pests and diseases are another challenge. Improvements in control measures and infrastructure will be essential to ensure that seeds are kept safe from these threats.
The Ultimate Safety Plan
For collections to be safely conserved long-term, an important step is for genebanks to send duplicate materials to additional locations. “Many collections have backlogs of seeds that are waiting to be reproduced for back-up storage. Because individual genebanks are vulnerable to natural and human-made crises, these backlogs could eventually result in the loss of unique crop diversity,” adds Giovannini.
Ideally, collections should be duplicated with at least one set of materials held in another country for safekeeping and another at the Svalbard Global Seed Vault.
The future of global agriculture relies on the focused and coordinated conservation of all crops and their relatives. Concludes Giovannini, “The world would be a poorer place without cucurbit diversity.”
Snapshots of Squash Diversity
Watch our short documentary and check out more enchanting photos of pumpkins and other “winter squash” from the Crops in Color Squash campaign.