Tor J. Johansen
Research Professor (OAP Agreement)
Abstract
Warmer temperatures due to global warming and use of climate-enhancing fbre covers makes it important to gain specifc knowledge of the temperature response in potato cultivars grown under Midnight Sun in northern Scandinavia. The temperature response was therefore studied in climate-controlled growth chambers under constant temperatures from 9 to 21 °C under a natural 24-h photoperiod in a greenhouse in Tromsø (69.7°N, 18.9°E), Norway, for the potato cultivars Gullauge (medium late) and Mandel (late). There was a strong response in both cultivars to temperature, with reduced developmental time from emergence and leaf formation to visible fower buds at increasing temperature intervals. Emergence was earlier for Gullauge than for Mandel, followed by no diference in development time between cultivars for subsequent developmental stages. Shoot dry matter weight per plant was highest at 12 °C and 15 °C for both cultivars, although with higher shoot biomass at harvest in Mandel than in Gullauge. Tuber yields and tuber dry-matter percentages were higher for Gullauge than for Mandel. Fresh weight yields and dry matter percentage for both cultivars were highest at 15 °C. Optimum temperature for above-ground vegetative development-rate was estimated to be 24.0 °C and 22.6 °C, for Gullauge and Mandel, respectively. In contrast, the respective temperature optima for developing tuber dry matter content were 16.6 °C and 15.6 °C. Lower temperature optima for below-ground developme below ground with optimumsa of around nt make potato a suitable crop for temperate and boreal climates with cooler autumn temperatures. Diferent temperature response for above- and below-ground development may be used for decision about when to remove climate-enhancing covers in response to the temperature during the season. This diference may also be important for developing temperature-based growth models for potato cultivars from emergence to tuber yields.
Authors
Jorge Poveda Pablo Velasco Antonio de Haro Tor J. Johansen Alex C. McAlvay Christian Möllers Jørgen A.B. Mølmann Elena Ordiales Víctor M. RodríguezAbstract
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Authors
Mette Thomsen Tor J. Johansen Eldrid Lein Molteberg Anne-Berit Wold Arne Hermansen Anne-Kristin Løes Hugh RileyAbstract
Several factors may define storability in root crops. In the following paper, preliminary results are presented from two experiments performed to test factors affecting storage quality of carrot. The study have focused on 1) soil loosening/soil compaction and 2) different cultivars of carrot and root age considered by the length of the growing period. The results so far indicate that the soil compaction had few effects on storability of carrot, but did seem to negatively affect the length of the carrot. Soil loosening reduced the occurrence of liquorice rot caused by Mycocentrospora acerina. Large differences were found in storability between the ten tested carrot cultivars and length of growing period tended to be negatively correlated to storability. We conclude that a number of precautions in carrot production may increase storability and thus economic performance.