The Embryo Culture Of BC₁and Fertility Analysis Of Hybrids F₁between Caucasian Clover And White Clover

Legume forages played an irreplaceable role in its quality, yield, palatability and soil improvement. As a result of the climate limitation, the legume forages still didn’t get rid of the current situation of cultivation monotony in the central and western regions of Inner Mongolia. To improve the present situation, the new herbage varieties of high yield, high resistance, and which were able to fix nitrogen need to be cultivated except alfalfa. The test used Trifolium ambiguum Bieb. cv. Mengnong No.1, which adapted to the climate conditions of the central and western regions of Inner Mongolia, as female parent. The advantage of the female parent was high yield and high resistance, and with no roots nodules that prevented fixing nitrogen was the defect. The white clover (T. repens L.) which had great nitrogen fixation ability introduced from the Greater Khingan Mountains was as male parent for distant hybridization breeding. On the basis of rearch by predecessors, white clover was used as recurrent parent to backcross with hybrid F1, and the technology of embryo in vitro culture was combined to explore the suitable conditions of growth and propagation for backcross embryo. The purposes of the test were to get BC1generation and provide possibilities for fertility restoration. Hybrids F1were turned out to be highly sterility after the morphology and cytology tests and didn’t bear seeds in the first2years. However, parts of hybrids F1, which accounted for88%, beared seeds from the third years. Therefore, the test studied the biological and cytological indicators and discussed the possible reasons of fertility restoration to the seeds of hybrids F1. The main results of the test were as follow:1. Both the modified MS medium and1/2MS medium could be used as the basic culture medium to backcross embryo in vitro culture. The suitable concentration of sucrose and CH was15g/L and250mg/L respectively. The best time of backcross embryo in vitro culture was14～21days after pollination. The suitable induction medium for roots culture was:1/2MS+CH(250mg/L)+KT(1.0mg/L)+2,4-D(0.5mg/L). The suitable induction medium for leaves culture was: MS+6-BA(0.5mg/L)+2,4-D(2mg/L).2. Each seeds of hybrids F1had life energy, and all of them had hard real-time. Mechanical treatment before germination could break the hard real-time property. 3. The somatic chromosome numbers changed between40and48, and some cells of individuals emerged into chromosome doubling phenomenon and mixoploid. The form of3-12hybrid F1plant seeds had a large variation. Its somatic cells contained48chromosomes, and its karyotype formula was:2n=6x=42m+6sm, which belonged to2B. The somatic chromosome numbers of hybrid6-3was44, and its karyotype formula was:2n=30m+14sm, which belonged to2A.