Wouldn’t be helpful to know about a problem before it arrives? Xylella fastidiosa is a bacterial plant pathogen that’s causing havoc with grape vines in America, olives in Italy and almonds in Spain. But is it a danger to New Zealand plants in another hemisphere? A study by Sandra Visnovsky and colleagues warns us that yes, it is. Fortunately, they way they know it’s a problem, means that New Zealand isn’t in trouble yet.
The New Zealand plants studied weren’t in New Zealand. Visnovsky and colleagues studied the plants in the University of California Botanical Garden at Berkeley. Xylella fastidiosa is present in the garden, so if the plants were at risk, they should have picked it up. The scientists took leaf samples from 130 different New Zealand plant species and tested them using three different DNA detection methods to make absolutely sure of their findings.
Nine different New Zealand plants were found carrying Xylella fastidiosa – including well-known species like mountain toatoa and koromiko. Most surprising was finding three different genetic variants of the bacteria, showing that these plants had been infected multiple times, rather than the infection spreading from one plant to another. Worryingly, while some of the plants clearly showed signs of disease, others looked perfectly healthy, but still carried the bacteria.
Keeping these carrier plants out of New Zealand is critical. The bacteria spreads through insects that feed on plant sap – and some of these insects are already present in New Zealand. Fortunately, finding out which New Zealand plants can carry the bacteria helps biosecurity teams know what to look out for. It also shows the value of botanical gardens as early warning systems – by growing plants from around the world, they can help us spot potential problems before they reach new shores.
Visnovsky, S.B., Kahn, A.K., Nieto-Jacobo, F., Panda, P., Thompson, S., Teulon, D.A.J. et al. (2024). Multiple genotypes of a quarantine plant pathogen detected in New Zealand indigenous plants located in a botanical garden overseas. Plant Pathology. https://doi.org/10.1111/ppa.14026 ($)
