The search for new spaces in which to live or survive better has always characterized man, animals and plants. Very often these plant migrants, opposed to prevent their spread, put in place mechanisms that allow their survival even in environments made hostile by defense interventions, in an attempt to become endemic. Finding, in simple words, forms of “peaceful” coexistence in the environment in which they arrived. If we tried to consider the term “migrant” in a non-negative and, above all, more transversal way and made an effort to consider the traits that bring the plant world closer to the animal world and to us humans, perhaps we would not be so scandalized. Indeed, we could find from these comparisons ideas and reasons to welcome with more empathy our fellow humans forced to migrate by climatic emergencies and not only


► The colleague Stefano Mancuso, well known for his studies of plant physiology and neurobiologyrecently in Prato he planted the Bosco delle Neofitedeliberately contravening the rules that require reforestation using “local” species, consciously choosing non-native plants. In fact, the scholar considers the concept of autochthonous to be outdated, since Today’s world is the result of continuous changes and migrations. These “alien” plants have been considered by Mancuso as migrants and some scientific societies have stigmatized the intervention and the comparison. Without wanting to enter into the controversy, also because the Florentine colleague knows very well how to counter criticisms on his own, I like to dwell on the comparison made, which I share.

The term “migrant”, unfortunately, in the common meaning it has taken on a negative meaning. But if we go to consider the meaning given by Treccaniwe see that this term refers to “a large number of people who emigrate or move looking for new places, … to animals, which migrate … and with meanings more technical, in biology and medicine, to cells or organs that have the capacity or possibility of moving – actively or passively depending on the case – from their usual location, for various reasons». In other words, we humans move and we have always moved in search of food, more fertile lands, better living conditions. Animals movealso in search of food, areas to colonize, climatic conditions more suitable for their survival. Plants move with seeds and trade and microorganisms move with them.. Everyone moves with the means at their disposal and/or by exploiting vectors, certainly in a more or less conscious manner.

The search for new spaces in which fundamentally being able to live or survive better has always characterized man, animals and plants. We are all of us aware that Migratory flows must be regulated and managed in some way. For us humans there are passports, residence permits, visas, etc. Animals and plants know and recognize borders much less than we do. In their case, to prevent “new arrivals” from causing problems (for example, the introduction of so-called invasive or alien species), supranational rules have been developed that are regularly updated (and not always respected). We are all aware of this. But this does not take away the fact that the comparison with migrants remains fitting and very effective. Leaving the speculations on plants to Professor Mancuso, I like to focus on microorganisms and, in particular, on pathogens capable of attacking plants, both cultivated and non-cultivated.

Molds isolated from snow collected in the Dolomites (credit Duccio Cavalieri)

These microorganisms (fungi, bacteria, viruses, …) know no borders and, as much as we try to counteract their movements and, in particular, their colonization of new areas, to avoid their settlement with damage to crops, they are able, often using goods and means of transport as carriers, to move even covering great distances. As true migrants. In some cases they move with the same plants that they are able to colonize and attack, which in turn move with the movement of plant material. International and shared phytosanitary standards provide methods and tools for the controls of imported plant material. But This does not mean that these populations of fungi, bacteria, etc. do not enter areas where, for various reasons, they are not wanted.. So, if we look carefully at their situation, they too can be considered real migrants. Very often These plant migrants, not welcomed with enthusiasm and opposed to prevent their diffusion, put in place mechanisms that allow their survival even in hostile environments. from defense interventions, in an attempt to become, let’s say with a technical term, endemic. Finding, in very simple words, forms of “peaceful” coexistence in the environment in which they arrived.

Salento olive trees attacked by the Xylella fastidiosa bacterium (credit Donato Boscia)

The careful study of “introductions” from the past (for example that of the Xylella annoying on vines in California in the late 1800s) also allows us to better understand the balances that are created between host plant and parasite. At the end of the 1800s a strain of Xylella annoying capable of attacking vines arrived in California, in the Los Angeles area. What were the consequences? Enormous damage to viticulture, which moved further south and the establishment of the bacterium in the Los Angeles area where it still survives in an endemic form. A few years ago, another strain of Xylella fastidiosa capable of attacking the olive tree arrived from Costa Rica, with ornamental plants and, not intercepted in Holland, arrived in Puglia. There Xylella he is a well-equipped migrant, able to hitchhike further thanks to insect vectors. We all know the end of the story in Puglia. And, if there is a solution, it will depend on the spread of olive varieties capable of tolerating the presence of the pathogen. After all, genetic improvement teaches us that the sources of resistance to parasites are sought precisely in the places of origin of the crops subject to those parasites. Why? Why in the places where the parasites originate, situations of “coexistence” are created which allow both the host and the parasite to survive.

With a bit of irony but with a grain of seriousness I tried to demonstrate that there is no point in wasting energy in sterile polemics. We are all migrants. Sometimes temporary: like researchers who “migrate” abroad to study at prestigious universities, the cows that “migrate” happily in the summer in the alpine pastures, the microorganisms that are transplanted into our intestine. And let’s think about the ornamental plants that have acclimatized in different areas, the microorganisms that, when artificially introduced into poor soil, make it more fertile. Finally, if we tried to consider the term “migrant” in a non-negative way and especially, more transversal and let’s make an effort to consider the traits that bring the plant world closer to the animal world and to us humansperhaps we wouldn’t be so shocked. Indeed, we could find from these comparisons that seem “pushed” ideas for approaching studies in the field of plant biology in a more holistic way. And reasons to welcome our fellow human beings with more empathy forced to migrate by climate emergencies and more. © ALL RIGHTS RESERVED