Genome Size Unaffected by Variation in Morphological Traits, Temperature, and Precipitation in Turnip

Genome size (GS) was proposed as proxy for gross phenotypic and environmental changes in plants. GS organismal complexity is an enigma in evolutionary biology. While studies pertaining to intraspecific GS variation are abundant, literatures reporting the adaptive significance of GS are largelymissing. During food shortage, Brassica rapa var. rapa (turnip) is used as food and fodder for sustaining the livelihood of residents in the Qinghai Tibetan Plateau (QTP), which is also known as “the roof of the world”. Thus, climatic extremities make this region a natural environment to test adaptive significance of GS variation in turnip landraces. Therefore, from the QTP and its adjacent regions (the Hengduanshan and the Himalayas), we investigated adaptive evolution of GS in turnip landraces. Tuber diameter of turnip landraces was found to be significantly correlated with most of the environmental factors. GS was also shown not to be associated with morphological traits, temperature, and precipitation. Moreover, principal component analyses based on the whole dataset trisected the landraces into three distinct populations based on landrace usage—Hengduanshan, QTP, and the Himalayas. Nonetheless, our cumulative dataset showed evidence of adaptation of turnip landrace to different environments throughnonassociated genomic and phenomic plasticity.