NRI, together with EMBL’s European Bioinformatics Institute (EMBL-EBI) and their African partners, have made a significant scientific breakthrough in unlocking the genomes of whitefly species – tiny agricultural pests that causes enormous problems for farmers and horticulturalists. The scientists describe as “euphoric”, the moment they knew they’d solved the puzzle and effectively ‘unleashed the genie from the bottle’.
Whitefly, Bemisia tabaci, is one of the top 100 crop pests in the world, causing damage to plants and spreading plant diseases. This tiny insect – an adult whitefly measures just 1 mm in length – causes billions of dollars’ worth of
damage to cassava, cotton, tomato and grain-legume crops, and threatens food security in the developing world.
The large collaborative team of scientists that pioneered this work are members of the African Cassava Whitefly Project (ACWP), funded since 2014 by grants issued by the Bill & Melinda Gates Foundation.
NRI’s Professor John Colvin who led the project, explains that a genome is the genetic code that determines what an organism is. He says, “it is fundamental to understanding all sorts of biological relationships. It is the key to understanding an organism, in that it tells you about its relationships to other species, about biochemical pathways, whether or not it will be resistant to insecticides and so on.”
The consequences of unlocking the whitefly’s genome in terms of its importance to agriculture, food-production and humanity, is equivalent to the impact made on medicine when geneticists mapped out the human genome. The effects will be just as far-reaching for people who rely on cassava, one of the crops blighted by whitefly. Cassava producers are among the world’s economically poorest and cassava is important for their staple food, for income and for food security in times of drought and hardship.
The team of scientists say they’ve unearthed a ‘goldmine of information’ and the ground-breaking discovery – which was 20 years in the making – is an unprecedented resource for tackling this pest and its associated plant-virus pandemics.
There are more than 40 whitefly species that, collectively, are still called, Bemisia tabaci. They all look exactly the same, so it’s by examining their genomes and unlocking the code that Professor Colvin and his team have been able to tell the difference between them, expanding hugely their understanding of the species’ complexities.
“It is infinite”, says Professor Colvin, “it’s like freeing the genie in the bottle and being able to ask it whatever questions we like. We can now do huge amounts of science, looking at why this one transmits viruses, why this one doesn’t, what are the interactions between the viruses and the proteins in the insect, why does it feed on cassava, why don’t the cassava’s chemical defences kill it and so on. Once you have this resource – the genome – the genie in the bottle – it’s all about how you use it. Generating these genomes is quite literally releasing an information bottleneck.”
In terms of the global impact, whitefly is also a colossal problem throughout the United States, Europe, Asia and Australia, causing enormous annual economic losses in vegetable, cotton and grain legume cropping systems.
Andy Yates, team leader at EMBL-EBI, adds, “insect vector genomes are playing an ever-increasing role in food security efforts. The role these genomic resources will play will be transformative in improving the health and wellbeing of over 800 million people around the world who rely on cassava as a food crop. Integration into large-scale analysis and visualisation platforms such as Ensembl is key to these efforts”.
The six sequenced and annotated genomes are freely available to access from the Ensembl Metazoa resource.
Dr Lahcen Campbell, ACWP lead bioinformatician explains, “these six new genomes represent a valuable resource in understanding many aspects of fundamental insect biology, but notably whitefly-transmitted plant pathogens and their direct impact on worldwide agronomy. The breadth of African and Asian whitefly populations in this study enabled the full potential of in-depth comparative genomics to be leveraged, to combat these prolific invasive pests.” He goes on, “the ACWP represents a major scientific and humanitarian collaborative effort; one that will continue to benefit some of the poorest people who rely heavily on disease-free and stable, food production.”
Dr Joachim Nwezeobi, ACWP bioinformatics PhD graduate emphasizes, “the positive impact from successfully tackling the cassava whiteflies will be felt, not only by subsistence farmers who would not have to worry all night that their toil and sweat could be rendered useless, but also by the strengthening of the cassava value-chain through consistent and reliable produce supply from local farmers”.
ACWP scientists are already busy using this new knowledge to create novel and durable whitefly control strategies for farmers in sub-Saharan Africa. Dr Sharon van Brunschot, ACWP project manager explains: “We are using the new information that we have unlocked in these insects’ genomes to engineer the plant so that it can defend itself from whitefly - without the need to use pesticide sprays. It’s comparable to giving the plant a vaccine that protects it from the insect and also the plant viruses that they carry and spread”.
Dr van Brunschot says that whitefly are very good at evolving pesticide-resistance rapidly, so the advantage of this technology is that we can combine and attack several vulnerabilities at once in the whitefly, making it nearly impossible for it to develop resistance. She goes on to say, “it’s the equivalent of giving humans several different vaccines – the Pfizer and Astra Zeneca for example – to provide a wider spectrum of immunity. It almost goes without saying that if farmers aren’t spraying chemicals around, then that’s a good thing for other beneficial insects and for humans. This is a ‘clean’ way of controlling pests that is also sustainable”.
A full list of authors and contributors to the ACWP
John Colvin; Maruthi Gowda; Rebecca Grimsley; Tadeo Kaweesi; Habibu Mugerwa; Joachim Nwezeobi; Susan Seal; Rekha Swamy; Sharon van Brunschot; Paul Muhindira Visendi - from the Natural Resources Institute, University of Greenwich, United Kingdom
Lahcen Campbell; Paul Kersey; Gareth Maslen; Andy Yates - from the European Molecular Biology Laboratory, The European Bioinformatics Institute, United Kingdom
Christopher Omongo - from the National Crop Resources Research Institute (NaCCRI), Uganda
Ibrahim Mohammad - from the Kebbi State University of Science and Technology, Nigeria
Joseph Onyeka - from the International Institute of Tropical Agriculture (IITA), Nigeria
Angela Douglas; Michael Stephens - from the Department of Entomology, Cornell University, USA
Hélène Delatte - from CIRAD, UMR PVBMT, La Réunion, France
Louise Cachenaut; Sarah Mieulet - École d’Ingénieurs de Purpan, France
Osnat Malka; Shai Morin - from the Department of Entomology, The Hebrew University of Jerusalem, Israel
Elvira Fiallo-Olivé; Jesús Navas-Castillo - from the Instituto de hortofruticultura Subtropical y Mediterránea, Universidad de Málaga, Spain
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