Effects of latitudinal climate conditions on quality attributes in Brassica oleracea

Abstract

Brassica is a genus of plants that includes vegetables that are widely used for human consumption and contain high levels of health-promoting compounds. These vegetables are grown in large parts of the world, and the environmental conditions where they are cultivated can affect several quality attributes. The research presented in this thesis examined how variation in growth conditions with latitudinal location can in uence both the content of specific health-promoting compounds and sensory attributes. Two cultivars of the species Brassica oleracea, broccoli and kale, were studied under controlled and semi-field conditions. Interest was focused on the variation in day lengths and temperatures associated with different latitudinal conditions, and also light quality and cold acclimation in relation to latitudinal changes. In broccoli, it was found that levels of glucosinolates, vitamin C, and avonols were sensitive to both temperature and day length. Furthermore, the content of aliphatic glucosinolates and avonols was highest at high temperatures (21/15 C) and short days (12 h), although in some experiments the levels of aliphatic glucosinolates were highest at lower growth temperatures. Far-red light seemed to reduce the content of glucosinolates and avonols. For vitamin C, the assessments showed that levels were insensitive to the field conditions and higher at low temperatures. A number of differences in sensory attributes were also observed. For example, several of the sensory attributes did not vary between study locations in Norway (Troms and Grimstad) but did differ from those noted in the southernmost summer location (Berlin). The content of glucosinolates in kale was affected less by pre-acclimation growth conditions and more extensively by cold acclimation temperatures. Thus the results provided by the work underlying this thesis indicate that the quality of Brassica vegetables is affected by the latitudinal location of cultivation, and this finding can help optimize quality of the plant and increase the awareness of differences related to this aspect.