Numerous studies show that plastid DNA is inherited biparentally in alfalfa (Medicago sativa L.). Mitochondrial DNA has been shown to be inherited in a uniparental-maternal fashion in a limited number of sexual crosses. This study investigated the inheritance of mitochondrial DNA in 54 alfalfa progenies from crosses between two cytoplasmic male sterile maternal plants and 54 paternal plants, representing each of the eight basic germplasm groups of M. sativa. Cloned mitochondrial DNA fragments from M. sativa were used as hybridization probes to identify polymorphisms in mitochondrial DNA for Eco RI restriction sites. Polymorphisms were analyzed for patterns of mitochondrial DNA inheritance. All progenies displayed the Eco RI mitochondrial DNA restriction pattern of the maternal parent, indicating that maternal mitochondrial inheritance predominates in alfalfa. The same progenies were also examined for their plastid DNA inheritance pattern. Plastid DNA displayed a mixed inheritance pattern, with both uniparental-maternal and uniparental-paternal inheritance. Variation observed between paternal parents for plastid transmission was absent for mitochondrial transmission.
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