Embryological studies of cross compatibility in the genus trifolium part 1 hybridization of trifolium pratense with some species in the subgenus lagopus

Kazimierska, E.M.

Genetica Polonica 19(1): 1-14


Accession: 005353280

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Germination of pollen grains of 9 Trifolium spp. (T. alpestre, T. angustifolium, T. arvense, T. desvauxii, T. hybridum, T. incarnatum, T. lappaceum, T. medium and T. rubens on the stigma of T. pratense was studied. Pollen of T. desvauxii, whose pollen tubes did not grow into the stigma tissue, germinated most weakly. Pollen of the remaining species germinated better, and after 3-4 h single pollen grains were found in the style at a depth of 3-4 mm. Pollen of T. pratense germinated successfully on the stigma of T. desvauxii; however, its pollen tubes did not grow into the style. On the stigma of T. hybridum, only few pollen grains of T. pratense germinated; their pollen tubes were short and rarely grew into the stigma. Pollen of T. pratense germinated weakly on the stigma of T. medium, and only single pollen tubes were found in the style. In T. pratense, T. hybridum and T. medium, used as maternal forms, the structure of the mature embryo sac was studied. The smallest embryo sac was that of T. hybridum; the embryo sacs of T. pratense and T. medium were huge. The size of cells of the egg apparatus and 2nd nucleus of the embryo sac depended on the size of the embryo sac. Out of 897 analyzed ovules, 4 of T. pratense were fertilized with pollen of T. medium, T. arvense, T. incarnatum and T. lappaceum. In one of the ovules, fertilization was double (T. pratense .times. T. lappaceum); in the remaining ovules, one of the sperm nuclei did not link with the egg cell or with the 2nd nucleus of the embryo sac, and in one of the embryo sacs no sperm nuclei performed fertilization. In the rest of the ovules, analyzed from 22 h to 8 and sometimes 12 days after pollination, no fertilization occurred. Causes of non-hybridization are considered. Weak germination of the paternal pollen on the stigma of the maternal plants and sporadic cases of fertilization are probably determined by deficient homology of the genome T. pratense with genomes of the crossed species. However, differences in the style length and diameter of the pollen grains, seem to present no obstacles for crossing.