Embryological studies of cross compatibility of species within the genus Trifolium L. III. Development of the embryo and endosperm in crossing T. repens L. with T. hybridum L. and T. fragiferum L

Kazimierska, E.M.

Genetica Polonica 21(1): 37-61


Accession: 000877861

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In compatible crosses within each of white clover, Alsike clover and T. fragiferum, 92.4-98.2% of ovules were fertilized, whereas 64.1-73.7% were fertilized in reciprocal crosses between these species. Embryo and endosperm development in the interspecific hybrids was slower than in the parental species, and stopped after about six days in hybrids. The hybrid embryo sacs died about eight days after fertilization, but endosperm was always present. Hybrid incompatibility was attributed to the incompatibility of complete genomes, which initiated disharmony between the developing embryo and endosperm. This genome incompatibility was also expressed in polyembryony, aposporic embryony, early transformation of the endosperm from the nuclear to the cellular condition and rapid development of the integumental tapetum, which were observed in some of the hybrid material. Differences among species and hybrids in the size and shape of endosperm nuclei are noted.