Study reveals why young plants have more difficulty fighting off diseases

A study by researchers at the University of Maryland offers new insights into why young organisms, including plants, are more susceptible to disease. The research suggests that fighting disease early in life can compromise plants’ growth and reproductive capacity later in life.

The research focused on the plant Silene latifolia, known as white bellflower, and how it deals with the fungal disease called anther-smut, which prevents the plant from producing pollen and, consequently, from reproducing.

While the disease doesn't kill the plant, it prevents reproduction, which has been compared to a "plant STD," according to Emily Bruns, assistant professor of biology at UMD and co-author of the study.

The study involved 45 genetic variations of Silene in a controlled environment. The researchers found that young plants with greater disease resistance had significantly fewer flowers and seeds over their lifetimes, even in a disease-free environment. On the other hand, adult plants with greater resistance did not suffer this penalty.

“The cost of fighting disease is higher for young plants, as they have limited resources and, by using them to defend against pathogens, they are unable to invest in future growth,” said Bruns.

The study revealed that while young plants expend more energy to fight the disease, they end up being more vulnerable to infection, which prevents the evolution of stronger resistance at this stage of life.

The researchers also created a mathematical model that illustrates how these high costs of combating pathogens are large enough to prevent the evolution of resistance in young plants.

In theory, plants with greater juvenile resistance could eradicate the disease, but the costs of developing this resistance prevent this from happening.

Another interesting finding was that males of the species Silene latifolia presented even higher costs to resist the disease compared to females. This may be because males produce a much larger number of flowers to spread pollen, which makes it more costly to divert resources to disease defense.

More information can be found at pnas.org/doi/10.1073/pnas.2419192122