| In order to cultivate suitable Trifolium varieties which can growth in Inner Mongolia condition and have exellent forage value, Trifolium ambiguum Bieb. with the characteristics of strong drought resistance, winter hardness and good quality and Trifolium repens L. which had great nitrogen fixation ability were selected to cross, and the some F1 generation strains with no fertility were obtained. After identification those F1 plants were transplanted into the test field for natural growth. During the first two years, F1 plants could normally grow and flower, and not produce seeds. However, most of the F1 plants produced seeds in and after the third years. Ten F1 strains (named 1-10, 2-4,2-5,3-7,3-11,4-1,4-2,4-7,5-8 and 5-12) which showed different morphological forms with higher seeding rates were chosen to observe the biological and cytological indicators of seeds and F2 strains that were compared with their parents. The main results were as follows:1. The seeds of ten F1 strains could germinate. But the percentage of hard seeds were quite high Significant difference was found in seed characteristics of 10 F1 strains, and the general characteristics were similar to female parent.2. the numbers of chromosomes of ten F2 strains were 2n=6x=48, equaling to those of female parent. But their structures of karyotypes were different. The chromosome of strain 3-11,4-1 and 4-7 each has a pair of satellites.3. Among ten F2 strains and their parents, the karyotypes of strain 5-8,5-12 and other eight strains belonged to 1B,2A and 1A. While the karyotypes of parents all belonged to 1A. The evolution degree of karyotype from high to low was as follows: Trifolium repens L.>4-7>4-1>110>2-4>4-2>3-7>Trifolium ambiguum Bieb.> 5-8>5-12>2-5>3-11.4. The morphological difference of hybrids were decided by the karyotype instead of the number of the chromosomes. |
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