Potatoes benefit when two soil bacteria team up

Potato is one of the world's most important food crops and feeds millions of people. Yet maintaining high yields often requires substantial chemical inputs such as fertilisers. Benedicte Albrectsen and her group at the Department of Plant Physiology and Umeå Plant Science Centre therefore investigated whether naturally occurring soil microbes could help support potato production in a more sustainable way.

"We wanted to know if two types of helpful bacteria work even better together than alone," says Benedicte Albrectsen.

The researchers focused on Pseudomonas protegens and Pseudomonas simiae, two well studied naturally occurring beneficial soil bacteria known to promote plant growth and health. They tested the bacteria individually and in combination to see how they affected potato plants and included different potato cultivars in the study.

Bacteria influence each other

When introduced to potato plants, the bacteria quickly established in the roots and influenced signals involved in tuber formation. The treated plants showed earlier signs of tuber formation than untreated plants, and gene expression analyses revealed increased activity of genes associated with tuber formation. In several cases, the combined treatment produced distinct responses that differed from those observed for the individual bacterial strains.

"We were pleasantly surprised. We anticipated positive effects but the synergistic interactions between the two bacterial strains were more pronounced than we expected," says Benedicte Albrectsen.

To better understand how the two bacterial strains interacted, the researchers analysed both the compounds produced by the bacteria and the responses triggered in the potato plants. With help from the Swedish Metabolomics Centre, they found that the bacteria released a unique mix of compounds when grown together, suggesting that the bacteria influence each other's behaviour.

Affected plant defence

The bacterial treatments affected not only plant growth but also genes involved in tuber formation and plant defence against stress and disease. This suggests that the bacteria influence both potato development and the plant’s ability to respond to challenges in its environment.

The researchers also found changes in tuber quality, including starch and vitamin C content. However, the responses varied between the potato cultivars ‘Mandel’ and ‘Désirée’, both of which are commonly grown in Sweden.

“We now want to test natural combinations of beneficial bacteria under field conditions to see if the greenhouse results translate to agricultural systems. What I find particularly fascinating is how the diversity of soil bacteria can shape potato growth and development. Understanding these interactions could also provide insights relevant to other crop systems,” says Benedicte Albrectsen.

About the study

Arti Mishra, Lovely Mahawar, Angeliki Tsitouri, Jasim Basheer, Benedicte Riber Albrectsen, Plant growth-promoting Pseudomonas strains modulate potato tuberisation signalling and development, Journal of Experimental Botany 2026, DOI: https://doi.org/10.1093/jxb/erag237