Abstract
EcoR1 restriction endonuclease analysis of chloroplast DNA isolated from several distinct populations of Nicotiana debneyi has revealed a naturally occurring polymorphism. The chloroplast DNA of seven of the nine populations analysed possessed an additional EcoRl site. The origin of the additional restriction endonuclease fragments was confirmed by hybridisation of [32 P]-cRNA to fractionated EcoRl restricted chloroplast-DNA fragments adsorbed to nitrocellulose filters. Reciprocal f1 hybrids between plants carrying the variant chloroplast-DNA's confirmed maternal inheritance of chloroplast-DNA.