Plant species’ genetic diversity and the role it plays in fighting disease

Viruses are found everywhere in the animal and plant kingdoms. But what makes some individuals more prone to disease than others? Using advanced techniques and tools, scientists supported by the EU-funded RESISTANCE project have been looking to the plant kingdom for the answer.

In a recent study whose findings were published in the journal ‘Nature Communications’, the researchers found that a number of different viruses are likely to infect the same host. They also discovered that the most important factor affecting virus diversity in nature is the host’s genetic make-up, or genotype. Given the rapid decline in the genetic diversity of natural populations, species could become more susceptible to infections and extinction.

Scientists already know that genetic differences can play a role in an animal or plant’s resistance against a specific virus. However, most organisms are hosts to more than one kind of pathogen. “Accounting for this diversity of infection is necessary to understand and predict disease dynamics and costs of infection for the host,” stated Prof. Anna-Liisa Laine in a press release posted on the website of project partner the University of Helsinki. The RESISTANCE team has now proven that genetic differences greatly affect virus diversity in an individual. “This suggests that depletion of genetic diversity within a species can have significant consequences for the risk of virus infection,” she observed.

The plant used in the study was Plantago lanceolata, commonly known as ribwort plantain. The RESISTANCE team created 80 clones from each of 4 different variants of the weed by propagating its roots. The clones were then placed amongst natural populations of ribwort plantain in four locations in the Baltic Sea’s Åland Islands during a seasonal virus epidemic. “By placing identical plants in different environments and keeping everything else constant, we could rigorously test the role of genetics,” explained Prof. Laine.

Leaves were collected twice during the experiment – at two and seven weeks – to find which of five common plant viruses had infected the ribwort plantain clones. The researchers found that 68 % of the 320 host plants were infected by at least 1 virus. Out of these infected individuals, 23 % hosted more than 1 virus. In total, there were 17 different combinations, ranging from 1 to 4 viruses in a single plant.Out of a number of factors, such as genetics, plant size, location, herbivore damage and virus-virus interaction, the differences in the plants’ virus composition seemed to be affected most by the hosts’ genetic make-up. “This demonstrates for the first time that genetic differences, most likely in immunity genes, are critical for how these diverse pathogen communities assemble inside hosts,” commented Prof. Laine. “One of the next steps will now be the identification of the underlying genes.”

The RESISTANCE (Resistance evolution in response to spatially variable pathogen communities) team’s findings indicate that loss of diversity can make species more vulnerable to virus infections and consequently result in the extinction of some. The study’s results could also inform agricultural practices with the aim of improving the virus resistance of crops. “Incorporating genetic diversity to crop systems should be embraced as a sustainable means of controlling disease in agriculture. Not only individual pests, but entire communities of pathogens,” concluded Prof. Laine.

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RESISTANCE project