Dna C-Value Variation In The Genus Arachis (Fabaceae)
EM Temsch and J GreilhuberUniversity of Vienna, Institute of Botany, Vienna, Austria
Correlations of plant nuclear DNA C-values with ecologically relevant parameters, such as elevation above sea level, geographical latitude, rainfall, and other stress factors, are increasingly being investigated. Especially when intraspecific variation of C-values is concerned, questions of the technical precision and reliability of the DNA content measurements become crucial. Here we summarize our work on C-values in Arachis (Temsch & Greilhuber, 2000, 2001)(2,3), an important legume, for which data in the literature were divergent and appeared suspect. We dealt especially with Singh et al. (1996)(1), who reported intraspecific 1.15-fold variation in the tetraploid A. hypogaea, and 1.10-fold variation in the diploid A. duranensis, its presumed wild progenitor. They also reported that in A. duranensis the C-values of 11 accessions correlate negatively with altitude a.s.l. of the localities of collection. Our re-analysis using flow-cytometry (PI as DNA stain) and Feulgen densitometry showed that:
1. In A. hypogaea there is no significant variation in DNA C-value among subspecies, varieties and accessions within these;
2. 2C-values given by Singh et al. (1996) are about twice as high as they should be;
3. the same bias applies to the data on A. monticola and A. duranensis;
4. C-values in A. duranensis actually vary 1.07-fold, but this variation does not correlate with the variation given by Singh et al. (1996) in the same accessions.
5. We also found a negative correlation of our C-values with elevation of sampling sites a.s.l., but
6. the negative correlation with altitude found by Singh et al. could not be reproduced by us, using the same accessions. The explanation for this is that Singh et al. selected 11 samples out of 28 to obtain such a fit. C-value stability in A. hypogaea and variability in A. duranensis are in agreement with publications on variation of molecular markers, which vary little in A. hypogaea but strongly in A. duranensis.
1. Singh KP, Raina SN, Singh AK (1996). Genome 39: 890-897.
2. Temsch EM, Greilhuber J (2000). Genome 43: 449-451.
3. Temsch EM, Greilhuber J (2001). Genome 44: 826-830.