The incompatible female is a-m(pa-pu)/a sh2 while the male parent in this incompatible pair is a et/a et. A partial seed set (less than 25 seeds per ear) is observed in this cross but in reciprocal crosses the seed setting is normal. The genetics of this partial cross-incompatibility was studied and the results indicate that three independently segregating recessive genes are involved. One gene pair named cif (cross-incompatible female) is expressed in the female and when in the homozygous recessive state, the plant is an incompatible female. When used with the appropriate male the other two genes cim1 (cross-incompatible male) and cim2 are expressed in the male. When both of the cim genes are in the homozygous recessive state, the result is a partial seed set. The putative genotype of the incompatible cross is cif/cif x cim1/cim1, cim2/cim2.
Normal seed setting is dominant over
reduced seed setting and this incompatibility is under the control of a
sporophytic system of incompatibility. It has also been observed that the
rejection of incompatible pollen occurs before fertilization. The mode
of rejection of incompatible pollen is under study.
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