What Is Brassica Rapa Var Rapa?

Brassica rapa var rapa (Man Jing Turnip) is an important biennial, outcrossing, mesopolyploid herbaceous plant in the family Brassicaceae, native throughout Europe, Russia, Central Asia and the Near East (Prakash & Hinata 1980 ) with Europe proposed as one centre of origin.. In the alpine regions of the Qinghai-Tibetan Plateau it was widely used as a food source, when other crop production was limited approximately 2000 B.C. These highlands range in altitude between 3000-4000 m and are characterized by strong UV-B radiation and low accessibility of water (Liu et al 2012). Although turnip is a cool season, drought and cold tolerant crop (4-18 ᵒC), it grows at higher elevation in tropical countries e.g India, Nepal, Bhtutan, Bangladesh, Srilanka,
The genetic diversity of B. rapa is documented by morphological characteristics (Padilla et al 2005), isozyme polymorphism (Persson et al 2004), RAPD (Yildirim et al 2009) and SSR (Ofori et al 2008) markers. It is a diploid species (AA=2n=20) with a small genome (1C=0.539±0.018pg, Johnston et al 2005) and published data suggest that it has a high rate of genome evolution (Wang et al 2011). The genome of B. rapa consists to about 39.5% of transposons (Wang et al 2011). B. rapa is an excellent model system to understand polyploid genome evolution due to availability of whole genome sequence information(Wang et al 2011) strong phylogenetic relationship with A. thaliana and other Brassica sister lineages possessing big GS, paleohexaploid ancestry (Mun et al 2010) and smallest GS among Brassica genus. It
From different places of China, twelve B. rapa landraces were collected and grown in the agricultural field to observe the morphological variation and genome size (1Cx) estimation in Kunming Institute of Botany (KIB), Chinese Academy of Sciences. Chromosome number was also evaluated for all landraces. Chromosome studies showed all the landraces were of uniform chromosome number (2n=20) (Fig 2A) and clearly defined histogram was observed for each landrace in internal standardization (Fig 2B). Using best practice flow cytometry, 1.16 fold variations (~15.5 %) in the nuclear DNA amounts was observed in our current study. Although, genome size was not correlated with altitude (r = -0.418, p=0.180 N=12) (Fig 2C), co-processing of the landrace differing in genome size produced distinct peak in flow cytometric histogram depicting true difference in GS existence among the turnip landraces of two elevation (1900 meter and 3825 meter) (Fig 2D). To understand molecular mechanism of genome size variation we selected two turnip landrace KTRG-B-2A (1900 meter elevation from sea level) and KTRG-B-06 (3825 meter from sea level) which show true difference in GS by flow cytometry (Fig