Phenological and physiological responses to abiotic parameters in rare potato cultivars (Solanum tuberosum L.)

Abstract

This research study was conducted to measure the impact of abiotic factors including various root zone temperatures on the phenology and physiology of four potato cultivars grown under controlled greenhouse conditions. Despite the known phenomena of promoted root growth in the presence of elevated temperature, little information is available on that of Solanum tuberosum L. particularly the low yielding cultivars. Further studies were conducted on these cultivars to explore the contributing factors to their health beneficial effects. In vitro cultured plantlets were acclimatized and after growing for 48 days in individual planting bags, no heat and warm root zone temperatures (20°C, 24°C, 28°C) were applied to potato plants cv. BP1, Salad blue, Pink Fir Apple and Highland Burgundy Red for a duration of 25 days. The plantlets received the same macro and micro elements as well as a prominent amount of water. Data was collected on a weekly basis. Further experiments were conducted to establish the effect of 100%, 50% and 25% water and nutrient in combination with the root zone temperature (RZT) 24°C. Ethanol extracts of the potato tubers were assessed for their total polyphenolic, flavanol and flavonol content as well as Trolox equivalent antioxidant capacity (TEAC), oxygen radical absorbance capacity (ORAC), 1-diphenyl-2-picrylhyddrazyl (DPPH) scavenging ability, ferric reducing antioxidant power (FRAP) and L-Ascorbic acid assays. High Performance Liquid Chromatography (HPLC) was performed for the individual polyphenols. All increased root zone temperatures had a positive effect on tuberization and enlargement compared to the control. A significant increase in tuber weight was observed when exposed to root zone temperature of 24°C. Cultivar Salad blue had the highest content L-ascorbic acid when exposed to 20°C root zone temperature. No flavanols were detected. The two main peaks with the HPLC method resulted in chlorogenic acid and caffeic acid, present in all samples but significant in cultivar Highland Burgundy Red. The outcome of this study demonstrated that judicious use of root zone temperature can effectively encourage tuberization. Furthermore, it provides useful information on the levels of Lascorbic acid and its potential health promoting phytochemicals in the selection of potato varieties. To date, pigmented potatoes are not regarded as a high value crop on the South African market, however its yield prospects as well as health-promoting benefits could have a positive impact on the South African Gross Domestic Product (GDP) and in the health of the population. Potato cultivar (cv.) Salad blue (SB) seem to be a drought tolerant crop with the ability to produce reasonable yields under severe environmental conditions. In order to promote cv. SB as a possible food security option for South Africa, there is a critical need for empirical information, describing some basic horticultural as well as oxidative response and vitamin C presence. The results of this study further indicated that there is no activity against M. smegmatis at the highest test concentration of 1000 µg/ml. Antiproliferative activity against liver hepatocellular carcinoma (HepG2) cells for their and was found to have IC50 values ranging from between 267.7 ± 36.17 µg/mL and > 400 µg/mL after 72 h of incubation suggesting that it is non-cytotoxic to the specific cell line tested. The present study provides useful information for farmers and health professionals in respect of increased yield and health-promoting benefits of a single potato variety.