| Three endemic species of cultivated Emmer wheat (9 strains of T. persicum,
4 strains of T. pyramidale and 4 strains of T. palaeocolchicum)
and 4 strains of wild tetraploid wheat collected in Zagros Mts. region (3
strains classified as T. dicoccoides and 1 strain classified as T.
araraticum) showed incomplete compatibility to squarrosa cytoplasm.
When these strains were used as male parents in the cross experiments, no
abortive seed were produced on the (squarrosa)AABB+1D plants.
These strains were differed from other Emmer wheats (AB type) in the response
to squarrosa cytoplasm, because they did not exhibited the zygotic
lethality in the nucleo-cytoplasmic combinations with squarrosa cytoplasm.
However, they were also different from AG type, because they showed segregation
in the development of F1 seedlings. The F1 seedlings
with 1D chromosome (2n=29) grew to normal plants, but the F1
seedlings without 1D chromosome (2n=28) turned to be midget plants
with extreme reduction of plant vigour and severe chlorophyll variegation
under low temperature. These strains were classified as AB' type. No difference in the response type were observed among the strains belonging to the same species, with exception of four strains of wild tetraploid wheat collected in Zagros Mts. region. These exceptional strains were classified as AB' type in this experiment, regardless they were named as T. dicoccoides or T. araraticum. However, in respect of cytological and morphological classification, TANAKA & KAWAHARA (1976) suggested that two of these strains (KU-8821A and KU-8821C) were intermediate strains between AB genome specics and AG genome species. The present results indicate that the genetic differentiation in compatibility to cytoplasm among tetraploid wheats correspond to the phylogenic differentiation of tetraploid wheats. Such a correspondence suggests that the compatible relation between nucleus and cytoplasm, as revealed in the present experiment, may have some relation with the differentiation of species in wheat and the relatives. The author wish to express his sincere gratitude to Dr. M. TANAKA of Kyoto University and Dr. G. Kimber of University of Missouri for supplying the seeds of tetraploid wheat strains used in the present experiment. |
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