GENETIC-VARIATION DETECTABLE WITH MOLECULAR MARKERS AMONG UNADAPTED GERM-PLASM RESOURCES OF CULTIVATED PEANUT AND RELATED WILD-SPECIES

Peanut germ plasm consists of the cultivated allotetraploid species Arachis hypogaea L. and a large number of wild species, which are nearly all diploids. Our previous work indicated a very low level of genetic variability in American cultivars, as assayed by restriction fragment length polymorphism (RFLP) analysis. Since American cultivars might represent a narrow genetic base, we expanded our study to include unadapted germ-plasm lines from the various South American centers of origin, Africa, and China, where considerable morphological and physiological variability has been reported to exist. Wild species of section Arachis were included in the evaluations since they show a high degree of variation when assayed by RFLPs. Three methods were used to assay for RFLP variation: (i) conventional RFLP analysis using random genomic clones from peanut and cDNA clones from peanut and alfalfa (Medicago sativa); (ii) polymerase chain reaction (PCR) amplification of random primer sequences; (iii) four-cutter analysis of PCR-amplified fragments. In all cases a very low level of variability was found in cultivated peanut, while abundant variability was present among wild diploid species. The results are discussed in terms of peanut evolution and significance to peanut breeding.