Plasmon analysis in the Triticum-Aegilops complex

This paper reviews our results on plasmon analysis of the Triticum-Aegilops complex after presenting the background and pioneering work. 1) Genetic effects of 47 plasmons of Triticum-Aegilops accessions on 21 wheat characters were analyzed using 12 euplasmic and 551 alloplasmic lines, in which 12 common wheat genotypes and 47 plasmons were combined in all possible combinations, except for one lethal combination. Characteristics of the individual plasmons on wheat phenotypes were clarified, based on which they were classified into 15 types. 2) Plastome and chondriome diversities were studied by RFLP analyses of chloroplast (ct) and mitochondrial (mt) DNAs, respectively. Based on the data obtained, numbers of differential mutations in the plastomes and genetic distances for the chondriomes were estimated for all pairs of the plasmons, based on which their phylogenetic trees were constructed. 3) Combining the results of the above works, 47 plasmons were classified into 18 types plus five subtypes, to which plasmon symbols were assigned. 4) Differentiation of the plasmon at the diploid level and maternal lineages of the polyploid species became elucidated. 5) Referring to the genome symbols designated by previous workers, the genome-plasmon constitutions of all Triticum-Aegilops species were clarified, based on which species relationships of this complex became established, the first example of the generic level throughout the plant and animal kingdoms. 6) Origins of some polyploid species were shown to be more recent than some other relatives, three examples being Timopheevi vs. Emmer group of tetraploid wheat, Ae. triaristata vs. Ae. ovata of the Polyeides section and Ae. ventricosa vs. Ae. crassa of the Vertebrata section of Aegilops, the former being of more recent origin than the latter in each pair. 7) Possible sites of plasmagene mutations responsible for three plasmon-controlled traits were located on the plastome or chondriome phylogenetic tree. And finally, 8) some unsolved plasmon-related problems were pointed out.