Associations among inbred lines as revealed by RFLPs and by a thermocycling
amplification methodology, Amplified Fragment Length Polymorphisms (AFLPs)
--J. S. C. Smith , M. Zabeau and S. Wright
Forty-eight publicly available inbred lines of maize were profiled using 58 RFLP clones each directed against a single restriction enzyme digest. A total of 370 bands were scored across all inbred lines. Genetic distances were calculated and cluster analysis was performed as described by Smith et al. (Theor. Appl. Genet. 80:833-840, 1990). These same inbred lines were also profiled by AFLPs. This is a methodology that takes advantage of DNA amplification technology but which differs from both 'classical' PCR and single random primer methods such as RAPD, AP-PCR and DAF. The AFLP method generates multi-banded profiles that can reveal extensive polymorphism among inbred lines of maize (Fig. 1). (The technology is currently patent pending; for further details, readers are recommended to contact Dr. Marc Zabeau, Keygene, Agro Business Park 90, P.O. Box 216, 6700AE Wageningen, The Netherlands, FAX (31)837024939.) Across 44 of these inbred lines (4 lines had missing data) a total of 135 AFLP bands were identified. Each inbred was scored for the presence or absence of each band; genetic distances and clusters were generated as described above. Associations among inbreds on the basis of RFLPs and AFLPs are presented in Figures 2 and 3, respectively. Both methodologies showed a clustering of inbred lines that were related by pedigree into similar groupings. However, associations among these groupings showed some differences. These data are preliminary in that additional RFLPs and AFLPs could be scored. However, they demonstrate that DNA profiles generated either by a probe based technology or by a DNA amplification technology both provide evidence of similar associations when inbreds are related by pedigree. With regard to aiding in a more complete comprehension of genetic diversity with regard to the assignation of inbred lines within heterotic groups, their further classification within these groups, and correlation of these data with performance data, AFLPs appear to offer researchers valuable and possibly fresh insights compared to RFLPs.
Figure 1. Detail from AFLP profiles of 20 maize samples including both inbred lines and hybrids for a single primer. Molecular weight ladders are arrayed on either side of the maize lanes.
Figure 2. Associations among 48 inbred lines as revealed by cluster analysis of RFLP data.
3. Associations among 44 inbred lines as revealed by cluster analysis
of AFLP data.
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