| Diversity of the chloroplast genome among Triticum
and Aegilops specie revealed by chloroplast dna restriction fragment
patterns Yasunari OGIHARA Laboratory of Genetics, Faculty of Agriculture, Kyoto University Kyoto, Japan The chloroplast genome of higher plants has homogeneous circular molecules ranging in size from 120 kbp in pea to 180 kbp in Spirodela. Chloroplast DNA (ctDNA) examined mostly contains a large inverted repeat sequence of 22-25 kbp, in which ribosomal RNA genes are involved. The chloroplast genome of wheat contains 135 kbp molecules and segment of the inverted repeat is 21.0 kbp in common with many other higher plant ctDNAs (BOWMAN et al. 1981). I present here the chloroplast genome diversity and phylogenetic relationships among Triticum and Aegilops species by comparing ctDNA restriction fragment patterns. Intact chloroplasts were isolated from leaves of 34 self-fertile alloplasmic as well as from six euplasmic lines of wheats (almost all Triticum and Aegilops species), followed by the method of KOLODNER and TEWARI (1975). Chloroplasts were purified from crude preparations using a discontinuous gradient made with 10, 40 and 75% Percoll solutions. Purified chloroplasts were lysed in a solution containing sodium lauryl sarcosinate and Proteinase K. Then, ctDNAs were isolated. The restriction patterns of these ctDNAs digested with eight restriction endonucleases (Bam HI, Eco RI, Hind III, Kpn I, Pst I, Sal I, Sam I, Xho I) could be classified into 13 types, in total. The physical maps constructed by Pst I and Sal I of ctDNAs of common wheat, Ae. squarrosa and Ae. uniaristata were about 0.2-0.5 kbp smaller than that of most other species. These clasification of ctDNAs was principally in agreement with that of cytoplasms which is based on nuclear-cyloplasm interactions. Most polyploids and their related diploids showed identical restriction patterns indicating the conservatism of chloroplast genome during speciation. The restriction fragment patterns of Emmer and Dinkel (common) wheats were identical with those of Ae. longissima, and different from those of all other diploids. The restriction fragment patterns of Timpheevi wheats were identical with those of Ae. aucheri. Ae. searsii and Ae. bicornis, and T. urartu and T. monococcum had the identical chloroplast genomes with each other. |