Environmental and genetic influences on growth, flowering, and nectar production in mānuka (Leptospermum scoparium J.R. Forst. & G. Forst.) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science, School of Agriculture and Environment, Massey University, Palmerston North, New Zealand
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2019
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Massey University
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Abstract
Dihydroxyacetone (DHA) in floral nectar of the Mānuka shrub, Leptospermum
scoparium (J.R. & G. Forst.) is a direct precursor to methylglyoxal (MGO) the bioactive
compound of manuka honey. Accumulation of DHA in Mānuka nectars varies between
trees, localities, and years. However, the reasons for this variability are largely
unknown and its origins in nectar are unclear. Since high DHA to total sugar ratios
(DHA/TSugar) in fresh honey result in high MGO in mature honey, it follows that
nectars with high DHA/TSugar will produce high-value honey indicated by a high
Unique Mānuka Factor (UMF®) attracting premium returns for the NZ honey industry
and NZ economy. It is key to further optimise both nectar and DHA production by
selecting for high producers. Selecting/developing varieties for maximum nectar
potential (NP) needs an understanding of the relative influences of genotype (G),
environment (E), and their interactions (GEI) on relevant trait expression. The
responses of genetic clones from three high yielding Mānuka lines expressing varying
levels of nectar DHA to temperature, light, and soil moisture were studied in controlled
environments. The relative performances of the clones were evaluated and
contributions of G, E, and GEI to aspects of their growth, flowering and nectar
production quantified.--Shortened abstract
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Figure 1.1 re-used with publisher's permission.
Keywords
Leptospermum scoparium, Effect of temperature on, Effect of light on, Effect of soil moisture on, Genetics, Growth, Flowering, Nectar