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Discovering the Roots of the Cause of the Great Potato Famine
Brad Day , IS-MPMI Reporter editor-in-chief , recently interviewed Hernán Burbano , Max Planck Institute for Developmental Biology , about the recent discover of HERB-1 , a strain of potato blight that triggered the Irish potato famine in the nineteenth century . Burbano , along with IS-MPMI President Sophien Kamoun , were part of an international team of scientists to make this incredible discovery using dried plants more than 120 years old . Burbano discusses the process and what this means for the MPMI community .
Q : First , congratulations on your recent discovery and manuscript . This is particularly exciting for many reasons , but in my mind , it solidifies the application of genomics as a means to travel back in time to understand agriculture practices , pressures , and culture . Can you speak a bit about the foundation this work lays for future similar studies ?
A : The retrieval of sequences from historic samples opens a window to the past . Instead of inferences based on extant genetic variation , ancient DNA ( aDNA ) sequencing permits traveling back to the past to inspect directly DNA sequences that are hundreds and thousands of years old . The field of aDNA has experienced a blossoming in the last 7 years thanks to the advent of high-throughput sequencing . Traditionally , the DNA sources have been fossilized tissue such as teeth and bone . The completion of the Neanderthal genome and of the genome of the bacteria that caused the Black Death in the fourteenth century has radically change our views on human origins and disease emergence and re-emergence . Inspired by these studies , we used as a DNA source dried plants stored in herbaria and carried out the first whole-genome analysis of a plant pathogen and its host . We have shown that it is possible to do genomics using herbaria samples , which opens up a big road given the vast amount of samples stored in herbaria all around the world . Our study is perhaps a proof-of-principle experiment of a new field that we can call herbarium ( meta ) genomics .
Q : What is the next big question this type of analysis might address ?
A : There are many questions in evolutionary biology that can be illuminated using aDNA : identification and timing of the key changes that allowed the domestication of crops , characterization of the diversity in historic crop material , understanding the colonization of new ecological niches by invasive or introduced species , studying the dynamics of past epidemics and the co-evolution of plant – pathogen interactions .
Q : From a molecular-assisted breeding approach , are we moving toward a point where we might understand — or elucidate — the breeding practice ( s ) of a particular crop or agricultural region from a historical standpoint ?
A : It is possible to retrieve DNA not only from herbaria samples but also from archeological material , e . g ., seeds and cobs . One can , for example , study the key genomic changes in crop domestication through time . It will also be possible to characterize the genetic diversity of crops prior to the advent of modern agriculture .
Q : Is it possible we might be able to understand at a molecular-genetic level which breeding practices worked , or did not work , and from that , identify the point in time when a trait or combination of traits that were not overtly visible might have led to the introduction of a weakness ?
A : We will be able to study genetic changes in domesticated crops through time . Given the vast amount of genetic resources available in some crops , e . g ., corn , it would possible to predict complex traits , such as flowering time , based on genome-wide genotyping of old ( ancient ) crops .
Q : What other complex traits or variables ( e . g ., environment ) might be overlaid with a study of this type ? How much further would you like to see future studies of this type take us ?
A : One of the great advantages of working with herbaria samples is that the date of collection of the samples is known . This information helps to calculate accurately mutation rates and , therefore , divergence times between different species or lineages within the same species . One can then correlate these changes with historical events . For example , in our study we have found that a great increase in genetic diversity in Phytophthora infestans falls into the time window of the first contact between Americans and Europeans during the Spanish conquest .
Q : In the paper , the list of authors represent a diversity of expertise in the plant sciences . How will future studies learn from this and leverage broad expertise to deduce complex problems for the betterment of agriculture ? What can we learn about the migration of pathogens from a study of this nature ? What is the influence of man versus nature on agriculture diseases ?
A : Collaboration between experts of different fields is the way to approach biological problems . All biological fields gain in freshness and novelty with the outsider view from experts of a different research area . This project has shown how the consequences of a plant disease vary depending on socioeconomic and political factors . Even though in the nineteenth century , the same P . infestans strain triggered the outbreaks everywhere , its effects were stronger in Ireland than in continental Europe . It has also shown us how the spread of pathogens is strongly associated with human activity . As I mentioned above , the burst of diversity in P . infestans coincides with the Spanish conquest , which starts a big movement of people , animals , and aliments in the New World and between the New World and Europe . We have observed also how the introduction of resistance in potato through breeding has been a major selective force for P . infestans . n
International Society for Molecular Plant-Microbe Interactions
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