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 Light-induced tuber greening is one of the most important quality defects of potato. Although varietal and maturity factors are known to affect greening resistance, physiological mechanisms of resistance are poorly understood. We proposed that physiological and biochemical factors within the tuber periderm provide resistance and hypothesised that resistance is primarily related to suberin content.  We investigated differences in the tuber periderm between genotypes and tuber maturities that varied in greening propensity. We examined suberin and light-induced pigment accumulation, and phellem cell development, and studied greening propensity in mutant and chemicallytreated tubers with enhanced suberisation.  Resistance to greening was strongly linked to increased suberin in the periderm, which varied with variety and tuber maturity. Furthermore, greening was reduced in mutant and chemicallytreated tubers with enhanced suberisation. Increases in phellem cell layers and light-induced carotenoids and anthocyanins were identified as secondary resistance factors.  Our work represents the first physiological mechanism of varietal and tuber maturity resistance to greening, expanding the known functionality of suberin and providing for the first time a biomarker that will aid producers and breeders in selection and improvement of potato varieties for greening resistance.

Light conditions in retail stores may contribute to potato greening. In this study, we aimed to develop a potato tuber greening risk rating model for retail stores based on light quality and intensity parameters. This was achieved by firstly exposing three potato varieties (Nicola, Maranca and Kennebec) to seven specific light wavelengths (370, 420, 450, 530, 630, 660 and 735 nm) to determine the tuber greening propensity. Detailed light quality and intensity measurements from 25 retail stores were then combined with the greening propensity data to develop a tuber greening risk rating model. Our study showed that maximum greening occurred under blue light (450 nm), while 53%, 65% and 75% less occurred under green (530 nm), red (660 nm) and orange (630 nm) light, respectively. Greening risk, which varied between stores, was found to be related to light intensity level, and partially explained potato stock loss in stores. Our results from this study suggested that other in-store management practices, including lighting duration, average potato turnover, and light protection during non-retail periods, likely influence tuber greening risk.

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Tuber greening is one of the major causes of quality loss in the potato industry, however, the impact of nitrogen in-field fertilisation on this visual defect remains unknown. Two field experiments, one in Tasmania with final N treatment rates of 40, 100 and 190 kg N ha -1 for Nicola and 35, 95 and 185 Kg N ha -1 for Maranca, and another in South Australia with N rates of 100, 200 and 300 kg ha -1 for Maranca, showed a positive linear relationship (R 2 = 0.99, 0.86 and 0.90, respectively) between tuber N content and tuber greening, as determined by chlorophyll content. However, increased N fertilisation rates did not directly translate to increased tuber N content, with responses appearing to be variety specific. We conclude that tuber N content is a risk factor associated with tuber greening, but the manipulation of tuber N content through N fertilisation rate is not straightforward and may depend on variety and location.