Variations in genome size of turnip landraces from two high-altitude environments

Abstract

Brassica rapa var. rapa (turnip) is considered a main source of food for the inhabitants of the Qinghai- Tibetan Plateau (QTP) and its adjacent highlands when other crops are scarce. The QTP ranges from lat. 25.59ºN to 39.49ºN and from long. 73.29ºE to 104.40ºE, whereas the Yunnan Plateau ranges from lat. 20.00ºN to 29.16ºN and from long. 96.00ºE to 110.19ºE. A comparison between the turnip landraces of two different plateau environments can provide a mechanistic insight into plant adaptation in highlands. The aim of this investigation was to understand the patterns in variation in genome size (GS) between the turnip landraces of two plateau environments. We used a wellestablished protocol to count chromosome number and performed propidium iodide flow cytometry to measure GS. No polyploidy was detected among the turnip landraces tested, and 15.5% variation in GS was observed between the landraces. No consistent pattern pertaining to GS variation emerged after the environmental variables were considered. Thus, we propose that such pattern may reflect the indirect effect of selection, random process, genetic drift, or some other factors on GS through interaction of life-form and phenotypic traits.