| Identification of reciprocal translocation chromosome
types in the emmer wheats, I. Triticum dicoccoides KOERN.
Taihachi KAWAHARA and Masatake TANAKA Plant Germ-plasm Institute, Faculty of Agriculture, Kyoto University, Kyoto, Japan The presence of reciprocal translocation in polyploid wheats offers us valuable clues in pursuing the evolution of wheat. RILEY et al. (1967) were the first to use informations on chromosomal interchanges in discussing the phylogeny of hexaploid wheat. However, most studies have not been conducted on a large enough scale to identify the "wild" chromosome type neither of each polyploid level nor of each species. This series of study is planned to clarify the "wild" chromosome structure with regard to reciprocal translocations in the Emmer group of tetraploid wheats. This paper deals with wild Emmer, T. dicoccoides. Materials used were 22 strains of T. dicoccoides from Palestine, Southeastern Turkey, Northern Iraq and Western Iran (Table 1). A Palestinian strain, 108-3, was arbitrarily chosen as a tester strain and later another strain, 108-5, was also used as a male parent. For cytological observations, young anthers were fixed in Farmer's solution and the aceto-carmine squash method was used. The average seed fertility was calculated from seed setting on three bagged spikes from a single plant. Chromosome parings and seed fertilities of F1 hybrids between various dicoccoides strains and strain 108-3 and/or 108-5 are shown in Table 2. So far as major reciprocal translocations are concerned, 108-5 shows similar cytogenetical behavior to 108-3 when crossed to other strains. Table 2 shows that of 22 strains examined, 20 belong to the same reciprocal translocation chromosome type as 108-3, but that the remaining two strains, 109 and 195, have different chromosome structures from 108-3. Hybrids 109 x 108-3 and 195 x 108-3 formed a tetravalent at meiosis. In the former combination, 65 per cent of the cells were 1IV+12II. In hybrid 109 x 195, 2IV+10II were observed in 57 per cent of the PMCs. Based on the present data, chromosome type of 108-3 was designated as the EA type and those of 109 and 195 were named the EB and the EC type, respectively. The formation of a tetravalent indicating a major reciprocal translocation is expected in the PMCs of hybrids between the EA and EB types and between the EA and EC types. Two reciprocal translcoations are expected between the EB and EC types. The present data indicate that the EA is the "wild" chromosome type of T. dicoccoides. Literature Cited RILEY, R., H. COUCOLI and V. CHAPMAN 1967. Chromosomal interchanges and the phylogeny of wheat. Heredity 22: 233-247. (Received Jan. 25, 1978) |