Influence of temperature on plant morphology traits and their relationship to relative growth rate in wild and cultivated Capsicum accessions

Abstract

SummaryIn the Netherlands, sweet pepper (Capsicum annuum L.) plants are grown in heated greenhouses. Lowering the greenhouse temperature results in a substantial reduction in energy use. In order to grow crops under lowered temperatures, cultivars are required which are adapted to such conditions. In this study, we compared the variance in adaptation to low temperatures in six cultivated sweet pepper varieties to that in a collection of ten wild and cultivated Capsicum accessions. The adaptation to lowered temperatures was defined in terms of variation in the difference in relative growth rate (RGR) between plants grown under different temperature conditions. Our results illustrated that within the group of sweet peppers, the variation in low-temperature tolerance was limited, and that sweet pepper breeders should exploit the genetic variation in wild relative species in order to breed for this trait. RGR, however, is difficult and expensive to assess. Therefore, we also studied which morphological plant trait (e.g. leaf, stem, and total fresh- and dry mass, plant height, leaf area, or number of leaves) could be used to simplify the selection of RGR. The relationship between RGR and the various morphological plant traits was dependent on the amount of variation present for these traits in the experimental group of plants. As a result, the practical use of any of these traits as a measure for RGR was limited. However, relative leaf growth rate (RLGR) was shown to be a good alternative measure for RGR.