Effect of traditional storage methods on post-harvest dormancy of Taewa Māori seed potato (Solanum tuberosum L.) in Aotearoa New Zealand : 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, Manawatu, New Zealand

Abstract

In the Solanaceae family, the potato (Solanum tuberosum L.) is one of the major tuber crops. In New Zealand there are potatoes called Taewa. Māori growers who grow these potatoes generally store the harvested seeds in dark places, at the ambient temperature and a large proportion of those growers generally store with dry fern coverage for at least four months before planting. The objective of this study was to evaluate the Māori storage method on the preservation of the seed potatoes. This experiment chose conditions to represent traditional methods, the major difference being temperature control. The Māori Storage Method (ambient and dark environment) was contrasted with the Conventional Storage Method for potatoes, which consisted of placing the potato seeds in a dark room at continuous temperature of 5˚C. The potato seeds used in the experiment were randomly selected, weighed. And then put into storage. Tubers were evaluated at 30-day intervals from the beginning to 120 days of storage. A randomized complete block design was applied with 3 blocks of the treatments. In the first experiment (2022), analyses of respiration rate, weight loss and sugar content were performed. In 2023 the same experiment was repeated with some changes i.e., measuring sprouting (length, width and number of sprouts in Taewa varieties), but not sugar content (SC), and doing respiration rate (RR) and weight loss (WL) again for comparison between the two trials. Data on the evaluated parameters were analysed using a linear mixed model (Mixed Procedure) with year, variety, storage method and their interactions as the fixed factors and block as the random factor following by a Tukey-Kramer test for multiple comparisons. An exponential regression model (Nlin Procedure) was applied to fit the data on the change of parameters evaluated, and the coefficients of determination (R2) for regressions were also calculated. The response variables (respiration rate, weight loss, and sugar content) presented characteristics of each variety, highlighting the Tutaekuri variety with the highest respiration rate and percentage of sugar content. The variety that showed the highest percentage of weight loss was Moemoe. The influence of environmental conditions during the storage period of the Māori method may have interfered with the dormancy period of Taewa potatoes in the response variables (respiration rate, weight loss, sugar content, and sprout). The tuber dormancy duration is largely dependent on the genotype along with pre-and postharvest conditions. The factor that most determined this characteristic was the storage temperature. In this experiment, storage temperature is the main environmental factor affecting tuber dormancy on Taewa potatoes. The tuber dormancy duration is largely dependent on the genotype along with pre-and postharvest conditions. In general, there is a lot of common ground between both cultural and commercial approaches to seed selection and storage.