| Mitochondrial DNA diversity among Triticum and
Aegilops species T. TERACHI, Y. OGIHARA and K. TSUNEWAKI Laboratory of Genetics, Faculty of Agriculture, Kyoto University, Kyoto 606, Japan. In order to characterize mitochondrial(mt) geonomes in Triticum and Aegilops, mtDNAs are isolated from cytoplasms of 20 species (27 accessions in total) as listed in Table 1, and their restriction fragment patterns with five enzymes (BamHI, HindIII, PstI, PvuII and XhoI) are analyzed. In paticular, cytoplasms of five Sitopsis species are included in order to reveal the cytoplasm donor of polyploid wheats. Different sources of cytoplasms for each of type 1b, 3 and 4 chloroplast(ct) genomes are also included because of some differences observed in their phenotypic effects on wheat characters. Intact mitochondria are isolated from etiolated seedlings by a modified method of Bonen and Gray (1980), and mtDNAs are purified by CsCl equilibrium centrifugation. Figure 1 shows HindIII restriction fragment patterns of mtDNAs from B, G, S, Sb, S1, SV plasma types. MtDNA of Ae. longissima(11) gives identical restriction pattern with those of T. dicoccum(22) and T. aestivum(52a), whereas mtDNA of Ae. aucheri(09) shows identical pattern with those of T. timopheevi(25) and T. zhukovskyi(51). These facts prove that Ae. longissima and Ae. aucheri have provided their mitochondrial genomes, and consequently their cytoplasms, to the Emmer Dinkel and Timopheevi groups of wheat, respectively. Mt DNA variations are observed among some cytoplasms having the identical ctDNAs. For example, mtDNAs of T. dicoccoides(21) and T. spelta(52b) are distinguishable from those of Ae. longissima group by two HindIII fragments, although, at least, 36 fragments are found in common. MtDNAs of T. araraticum(23, 24) are distinguished from those of Ae. aucheri group by five of 69 HindIII fragments in total. Six cytoplasms having type 1b chloroplast genome are classified into four types (i, j, k and 1) from their mtDNA restriction pattern. The i, j, k and 1 types have three, two, three and three unique HindIII fragments, respectively, in additon to 42 commom fragments. MtDNA of Ae. bicornis(12) and those of Ae. kotschyi(33) and Ae. variabilis(34) have nine and eight unique HindIII fragments, respectively, besides 113 common fragments. MtDNAs Of two Ae. mutica lines (13, 14) differ from each other by eight and 11 unique HindIII fragments though 36 fragments are the same between them. Results of the restriction endonuclease analyses with HindIII and four other enzymes are summarized in Table 1. Mitochondrial genome designation given in it is tentative. The results clearly indicate that the mitochondrial genome shows higher variability than the chloroplast genome in Triticum and Aegilops. Thus, the mtDNA variability can be useful objective in the studies of interspecific relationship and intraspecific variation of the cytoplasm. |