Mānuka: defending grapevines from fungal attack

Leptospermum scoparium, known as tea tree or mānuka, is native to Australia and New Zealand. This iconic plant has been historically used across several industries, including honey production, meat seasoning, and in the pharmaceutical industry as an essential oil for medicinal use. However, there is another potential use related to agriculture. Mānuka has been studied recently at the microscopic level by a Lincoln University research team, including associate professor Eirian Jones, Jana Monk, Hayley Ridgway and graduate Wisnu Wicaksono.

In 2017, they published a research article that provides evidence that some mānuka endophytes have biocontrol properties. But what does that mean? Well, humans, other animals and plants are large living organisms that are inhabited by microscopic fauna. Endophytes include mainly fungi and bacteria that colonize plant cells. Their presence is often beneficial for both plant and endophytes. Usually, they engage in mutualism but these relationships are not fully understood and many of them have never been studied. Manuka endophytes may represent a potential biocontrol strategy against plant pathogens.

Mānuka tree in Strahan, Tasmania, Australia. CC BY 2.0 John Tann

Mānuka and grapevine plants (Vitis spp.) are both part of the Rosidae taxonomic subclass but they are completely different plants. Endophytes are shared across distantly related plants species and provides a relevance of mānuka for crop plants, such as table grapes and grapevines.

Trunk pathogens are a major concern for grapevine production. Botryosphaeriaceous species are a  causal agent of some grapevine trunk diseases. They cause wood cankers that disrupt water and nutrients flow and  there is also transport of toxins to the shoots. Affected vines are not curable. The only means of eradicating a trunk pathogen is by physically cutting out infected tissues. But this is not always feasible and the whole plant must be replaced. Botryosphaeriaceous pathogens have been detected in mānuka plants but there is no evidence that their presence affects this host.

Although mānuka’s flower is not used to make tea, its pollen has commercial value CC BY 2.0 Niggel Morris

Lincoln’s Pest Management and Conservation team discovered that indeed, endophytic bacteria present in mānuka can be transferred to grapevines. Pseudomonas sp. isolates I2R21 and W1R33 found in mānuka were successfully inoculated onto grapevine wounds which then inhibited Neofusicoccum luteum and N. parvum colonization, both botryosphaeriaceous pathogens.

The study showed that mānuka can provide endophyte species that are transferable to grapevine plants. It also underscores the values of the genetic resources found in wild biodiversity for agriculture and horticulture. These are relevant findings, as available options to control botryosphaeriaceous species are limited and there are few biocontrol agents that are as sustainable.

Personally, I will have the opportunity to be involved with Lincoln plant pathologists and conduct research related to endophytes present in grapevine plants. I am honoured to add to this legacy!

Reference: Wicaksono, W. A., Jones, E. E., Monk, J., & Ridgway, H. J. (2017). Using bacterial endophytes from a New Zealand native medicinal plant for control of grapevine trunk diseases. Biological Control, 114, 65-72.

 

The author Fernan Paniagua Madrigal is a postgraduate student from Costa Rica enrolled in the Master of Horticultural Science at Lincoln University. He wrote this article as part of his assessment for ECOL608 Research Methods in Ecology.

 

Leave a Reply

Your email address will not be published. Required fields are marked *