University of Munich

STUTTGART, GERMANY

University of Hohenheim

Comparisons among strains of inbreds for RFLPs

--J. Boppenmaier, A. E. Melchinger, E. Brunklaus-Jung and R. G. Herrmann

We have analyzed RFLP patterns of different strains of five inbred lines, developed by W. G. Pollmer from the University of Hohenheim (Table 1). The lines have been released between 1968 and 1981. They had been maintained in separate breeding programs in Germany for one to eight generations by selfing or sibbing and rogueing off-type plants.

The various strains from each inbred were analyzed for their respective RFLP patterns using equal quantities of leaf tissue harvested from five seedlings per strain. Genomic DNA was digested separately with restriction enzymes EcoRI and HindIII. RFLP analyses were performed with a total of 101 genomic DNA clones kindly provided by D. Hoisington (University of Missouri, Columbia, MO) and B. Burr (Brookhaven National Laboratory, Upton, NY).

For inbred DK105, two strains (B and C) showed identical RFLP patterns for 101 DNA probes with both restriction enzymes. These two strains had been highly inbred (S12) before being maintained separately for two to eight generations. Strain A had identical RFLP patterns with strains B and C for 99 of the 101 DNA probes. However, different RFLP variants in A than B and C were found with both enzymes for DNA probes BNL5.09 and UMC106, mapping to chromosomes 9 and 1, respectively.

For inbred D140, the two strains showed different RFLP banding patterns with both enzymes only for a single DNA probe (UMC116), mapping to chromosome 7. The other three inbreds (D503, D406, and D44) showed identical RFLP patterns for both strains with all 101 DNA probes examined.

The small numbers of polymorphic RFLP loci found between different strains of the same inbred lines indicate that the lines had been highly homozygous as expected from the respective number of selfing generations before separate strain maintenance. In addition, our findings are in agreement with an earlier report (Evola et al., Theor. Appl. Genet. 71:765-771, 1986) that RFLPs are stably inherited over several selfing generations. In contrast, Godshalk and Lee (MNL 64:58, 1990) reported a significant number of polymorphic RFLP variants in different strains of maize inbred W22 maintained in separate breeding programs. In combination with high level of polymorphisms at RFLP loci found in maize (Melchinger et al., Crop Sci. 30:1033-1040, 1990), our results corroborate that RFLPs should be a valuable tool for identification of maize inbred lines for plant variety protection, registration, and patenting.

Table 1.  Line maintanance of five maize inbred lines in separate breeding programs and number of DNA probes revealing RFLPs among different strains.

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