It is generally agreed that flow cytometric estimation of nuclear DNA amount in absolute units should be performed using internal standard (the nuclei of a standard are isolated, stained and analysed simultaneously with the nuclei of a sample).
To estimate nuclear DNA content in plants, most laboratories prefer to use plant DNA standards. When choosing a standard, it is advisable to select a taxon whose DNA amount is not very different from that of a sample (this will decrease a risk of errors due to nonlinearity of the instrument). Several species are thus needed to cover the large range of genome size known for plants. Unfortunately, there is no general agreement on DNA standards for plant flow cytometry. This laboratory has been using the following plant cultivars:
Species | Cultivar | 2C DNA Content (pg)* | 1C Genome Size (Mbp)** | Reference |
---|---|---|---|---|
Allium cepa | Alice | 34.89 | 17 061 | Dolezel et al. (1998) |
Vicia faba ssp. faba var. equina | Inovec | 26.90 | 13 154 | Dolezel et al. (1992) |
Secale cereale | Dankovske | 16.19 | 7 917 | Dolezel et al. (1998) |
Pisum sativum | Ctirad | 9.09 | 4 445 | Dolezel et al. (1998) |
Zea mays | CE-777 | 5.43 | 2 655 | Lysak and Dolezel (1998) |
Glycine max | Polanka | 2.50 | 1 223 | Dolezel et al. (1994) |
Lycopersicon esculentum | Stupicke polni tyckove rane | 1.96 | 958 | Dolezel et al. (1992) |
Raphanus sativus | Saxa | 1.11 | 543 | Dolezel et al. (1998) |
*) Nuclear DNA content was established using human male leukocytes (2C = 7.0 pg DNA; Tiersch et al. 1989) as a primary reference standard.
**) 1 pg DNA = 978 Mbp (Dolezel et al. 2003)
All cultivars fulfil the criteria for plant DNA standards as they are: a) suitable for flow cytometric analysis of DNA content; b) seed propagated; c) available as elite lines from breeders. Upon request, this laboratory can provide reasonable amounts of seeds free of charge. Please, send your requests to: dolezelueb [dot] cas [dot] cz