| A segregation experiment was performed to examine B1F1
plants obtained from backcrosses of F1 midget plants produced
by crosses of (squarrosa)AABB+1D lines of AB type Emmer wheats
x AB'type Emmer wheat species (as male). When the F1 midget plants
were backcrossed with AB type Emmer wheat species (as male), half of the
B1F1 seed obtained were viable and the remaining half
abortive. And, the viable B1F1 seed produced midget
plants without an exception. On the other hand, when the F1 midget
plants were backcrossed with AB' type Emmer wheat species (as male), the
B1F1 seed obtained were all viable, no abortive seed
appearing. In the B1F1 lines produced from the B1F1
seed, four plant types, i.e. intermediate-I plant (without variegation,
half reduction of plant vigour), weak plant (without variegation, extreme
reduction of plant vigour), intermediate-II plant (with chlorophyll variegation,
half reduction of plant vigour), and midget plant (with chlorophyl variegation,
extreme reduction of plant vigour) were produced, in the ratio of 1:1:1:1.
The results suggest that AB' type AB genomes possess two kinds of nuclear genes controlling incomplete compatibility with squarrosa cytoplasm, which genes are inherited independently. One of the two alleles, which relates to the appearance of viable seed (shriveled because of incomplete development of endosperm) and the appearance of chlorophyll variegation, is regared as the nuclear gene controlling plastid development. The other, relating to plant vigour in B1F1 plants with squarrosa cytoplasm, is thus regarded as the nuclear gene controlling compatibility with the cytoplasmic factor relating to plant vigour (maybe mitochondrion). When the two nuclear genes controlling compatibility with cytoplasmic factors are designated Cp (gene for plastid) and Cv (gene for plant vigour), segregation observed in the B1F1 plants can be explained as Table 2. Genetic differentiation of these nuclear genes responsible to the compatibility with cytoplasmic factors were considered to be corresponding with the genetic differentiation of cytoplasmic factors among tetraploid wheats. Literature Cited OHTSUKA, I. 1983. Classification of tetraploid wheat based on response to Aegilops squarrosa cytoplasm and origin of Dinkel wheat. Proc. 6th Int. Wheat Genet. Symp., Kyoto, Japan, 1983: 993-1001. |
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