Plant & Food reports on an array of research projects

Plant & Food Research has posted accounts of four research projects on its website in recent days. They deal with the medicinal powers of horopito, the control of codling moth, the trial of a hop cultivar, and stabilising vitamin C.

Bacteria in the medicinal plant horopito

Endophytic bacteria play crucial roles in plant development by enhancing plant metabolism, improving nutrient uptake, influencing overall fitness, and mediating biological control of phytopathogens.

Microbial communities differ between plant species and characterising them could advance understanding of their key roles in plant health and ecology. However, there is limited information on the composition of endophytic bacteria found in the tissues of native medicinal plants. Pseudowintera colorata (horopito) is a primitive angiosperm and native New Zealand medicinal plant recognised for its antimicrobial properties.

For the first time, scientists from Lincoln University, AsureQuality, and Plant & Food Research have described the bacterial endomicrobiome of P. colorata.

In this paper, the diversity and abundance of bacterial endophytes in P. colorata were influenced by tissue type. However, several species found commonly throughout the plant were determined to be part of the “core endomicrobiome”. Some of the bacteria were able to inhibit the growth of selected phytopathogenic fungi in culture, indicating they may have potential as biocontrol agents.

All the tissues sampled (roots, stems and leaves) contained at least one culturable endophyte. These results support the theory that every plant on earth is colonised by microorganisms.

Characterisation of a core endomicrobiome of P. colorata has identified the key bacteria that are likely to be important for the plant’s physiological processes. Pseudowintera colorata contains several culturable endophytic bacteria with antimicrobial properties, some of which were able to improve plant growth. Future study into the roles of selected members of the endomicrobiome could further identify their functional importance in this plant.

Journal Reference:
Purushotham N, Jones E, Monk J, Ridgway H 2020. Community Structure, Diversity and Potential of Endophytic Bacteria in the Primitive New Zealand Medicinal Plant Pseudowintera colarata. Plants https://doi.org/10.3390/plants9020156

Unmanaged host trees of codling moths pose risks to apple industry

The New Zealand apple industry has achieved great success in controlling codling moths on orchards using biocontrol to meet the increasing demands for sustainable ultra-low residue fruit and strict phytosanitary requirements of over 60 export markets.

Since adult codling moths can fly several kilometres, depending on wind conditions and topography, on-orchard control alone would never eradicate the regional population. Researchers from Plant & Food Research and the University of Auckland set out to assess the uncontrolled populations of the pest in the peri-urban area of Hawke’s Bay, the heart of the New Zealand apple industry. Assessments were conducted in Hastings, a city of 70,000 people surrounded by commercial apple orchards, and Ongaonga, a small rural settlement near a pilot codling moth eradication zone.

Using sex pheromone traps, the research team caught nearly 1,000 moths in one season in Hastings. The catches were heavily clustered around host trees such as backyard walnut and apple trees across different suburbs. Many host trees in Ongaonga surrounding the pilot eradication orchards also had populations of codling moths.

The findings highlight the external risks the industry continues to face and the importance of integrating town and country in pursuing area-wide suppression and reducing the risk of migration of codling moths from peri-urban host trees to commercial orchards. An expansion of the successful Sterile Insect Technique (SIT) programme could be one of the special measures on the cards.

Journal Reference
Horner, R.; Paterson, G.; Walker, J.T.; Perry, G.L.; Jaksons, R.; Suckling, D.M. Will Peri-Urban Cydia pomonella (Lepidoptera: Tortricidae) Challenge Local

Can New Zealand hops help during fasting?

Amarasate™ is the extract of a hop cultivar bred by Plant & Food Research and only grown in New Zealand. The extract was identified as part of the government-funded Foods for Appetite Control programme which screened over 900 plant extracts for their potential in controlling appetite.

In this randomised, double-blind cross-over clinical trial, conducted by Plant & Food Research, Amarasate™ reduced feelings of hunger in 30 healthy, young men who undertook a 24-hour water-only intermittent fast.

The men were given either Amarasate™ or a placebo and assessed to determine how hungry they get throughout the day. When taking Amarasate™ the men reported a significant reduction in hunger, most notable when skipping a lunchtime meal 18h into the fast. Additionally, the men reported maintaining a greater feeling of fullness when taking Amarasate™ compared to the placebo.

These results suggests that people who are undertaking periods of fasting to manage their food intake – such as intermittent fasting regimes which are gaining popularity currently – may benefit from using Amarasate™ to keep their hunger at bay during their fasting periods.

Journal Reference:
Walker E, Lo K, Tham S, Pahl, Lomiwes D, Cooney J, Wohlers M and Gopal P 2019 New Zealand bitter hops extract reduces hunger during a 24 h water only fast. Nutrients 11 (11) https://doi.org/10.3390/nu11112754

Are there more stable forms of vitamin C?

Vitamin C is a critically important nutrient for human health. Most people are aware that vitamin C is responsible for maintaining a healthy immune system. It also supports normal brain function; the health of cartilage, collagen and connective tissue; and our veins and arteries. It contributes to normal growth and development in children; helps us absorb iron from our food; and helps reduce tiredness and fatigue.

One of the challenges with vitamin C, especially in processed products, is its instability. To combat this, additional vitamin C is often added to processed products to boost the natural content. When vitamin C is used in cosmetics and pharmaceuticals its structure is stabilized by adding a sugar molecule to it.

All plants produce vitamin C, which they use to protect themselves from potentially harmful by-products created during photosynthesis. In nature most plant-based chemicals can be found with modifications, especially added sugars, to their basic chemical structures. But for vitamin C, a modification with the naturally occurring added sugar is rare, only occurring in goji berries and zucchini, and hard to find in other foods, until now.

Using advanced plant chemical identification techniques, such as mass spectrometry and nuclear magnetic resonance spectroscopy, Plant & Food Research and University of Otago scientists have recently discovered this form of vitamin C can exist in crab apples.  It naturally has the stabilizing sugar molecule attached, but present in low enough concentrations not to increase the overall sugar content meaningfully. This opens up the possibility of breeding new apple cultivars, through conventional techniques, that have more of the stable vitamin C form, which could result in healthier fresh apples and processed apple products.

Journal Reference:
Richardson AT, Cho J, McGhie TK, Larsen DS, Schaffer RJ, Espley RV and Perry NB 2020. Discovery of a stable vitamin C glycoside in crab apples (Malus sylvestris). Phytochemistry https://doi.org/10.1016/j.phytochem.2020.112297

Source:  Plant & Food Research

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