Regional, Annual, and Individual Variations in the Dihydroxyacetone Content of the Nectar of Ma̅nuka (Leptospermum scoparium) in New Zealand

Abstract

A method was designed and validated for analysis of dihydroxyacetone (DHA) in the floral nectar of mānuka (Leptospermum scoparium). The method was applied to samples collected from different regions of the North Island and the Nelson region of the upper South Island of New Zealand during the period 2009-2012 as well as to nectar samples from some Australian Leptospermum species. The ratio of DHA to total sugar (DHA/Tsugar) was classified as low (less than 0.001 mg mg-1), moderate (0.001-0.002 mg mg-1) and high (>0.002 mg mg-1). Inter- and intra-regional variation were observed as well as inter-annual variation with variation from low to high classification occurring within one region and from low to moderate between years. Australian species also demonstrated elevated levels of DHA in the nectar. Some garden cultivars were shown to produce very high levels of nectar DHA/Tsugar and a survey of cultivars was undertaken; cultivars with single flowered red or pink flowers were the most common producers of very high levels of nectar DHA/Tsugar