Stuty On The Interspecific Hybirds Between Brassica Rapa And Brassica Oleracea

Distant hybridization plays an important role in crop genetic improvements. The allotetraploidsobtained by the way of distant hybridization between different species or genus were not onlyartificially created breeding materials but also provided a basis for further creating alien addition lines,alien substitution lines and translocation lines. Brassica rapa and Brassica oleracea are importantspecies of the genus Brassica and they have their respective advantages. B.rapa including B.rapa L. ssp.pekinensis, B.rapa L. ssp. chinensis and B.rapa L. ssp. rapifera, etc. B.oleracea including B.oleraceavar. capitata, B.oleracea var. botrytis L., B.oleracea var. alboglabra and B.oleracea var. italica, etc. Inorder to obtain new germplasm resources and build a basic for germplasm inovation and genetic study,interspecific hybridization between B.rapa and B.oleracea were carried out. In this study, B.rapapekinensis and B.rapa chinensis var. utilis of B.rapa, and B.oleracea var. capitata, B.oleracea var.italica and B.oleracea var. alboglabra of B.oleracea were used as research materials. The hybrids ofB.rapa chinensis var. utilis×B.oleracea var. italica, B.rapa pekinensis×B.oleracea var. capitata andB.rapa chinensis var. utilis×B.oleracea var. alboglabra were obtained by bud pollination and ovuleculture. The characters of hybrids F1and BC1plants, the pollen fertility and the chromosomecomponents were investigated. The main results and conclusions are as follows:1. In the general hybridization between B.rapa pekinensis and B.oleracea var. capitata, when B.rapapekinensis were used as female parents, two seeds were obtained. By embryo rescue,57hybridplants were obtained. The number of chromosomes of2seedlings and57hybrids were investigatedand the results revealed that2seedlings and4embryo rescued plants had twenty chromosomes,they were false hybrids.47of the embryo rescued plants had the anticipated chromosomes (2n=19)and the pollen fertility was aborted;6of the hybrids had38chromosomes and the plants werefertile. In the reciprocal cross, one seed and7embryo rescued plants were obtained and thechromosome number and pollen characters were also surveyed. The results showed that theseedling and6embryo rescued plants were real hybrids, they had19chromosomes and the fertilitywas aborted. One embryo rescued plants had38chromosomes and it was fertile. Thecrossing-compatibilities were different between different cross combinations and the probability ofhybrids was related to genotyle of female parents.2. In the general hybridization between B.rapa chinensis var. utilis and B.oleracea var. alboglabra,few seeds were obtained in the direct cross combination, but no seeds were obtained in thereciprocal cross combination. When B.rapa chinensis var. utilis were used as female parent,69hybrid plants were obtained. By cytological identification and investigation of pollen characters, itshowed that62of them had the anticipated chromsomes (2n=19) and the pollen fertility wasaborted;2of the hybrids had38chromosomes and the plants were fertile. However, in thereciprocal cross combination, only16hybrid plants were obtained,13of them had19chromosomesand they were sterile, no naturally doubling plants were founded.3. The different concentrations of colchicine were used to treat sterile hybrids F1between B.rapa chinensis var. utilis and B.oleracea var. alboglabra. The results showed that the frequency ofchromosome doubling was directly affected by the methods of colchicine treating. The variationrates of root pruned plants were lower than the normal plants. The treatment of root with0.4percentof colchicine solution for18hours and0.2percent of colchicine solution for40hours produced thebest results of chromosome doubling. The plants with doubled chromosomes were chimera andonly few flowers were fertile.4. The hybrids F1of B.rapa chinensis var. utilis×B.oleracea var. italica, B.rapa pekinensis×B.oleracea var. capitata and B.rapa chinensis var. utilis×B.oleracea var. alboglabra had manycharacteristics from both parents. The BC1plants were obtained through back cross between fertilehybrids F1and the female parents. Most characters of hybrids F2and BC1plants separating in thefield and the BC1plants were similar to female parents. Large differences of morphologicalcharacters were observed among three kinds of allotetraploids obtained by different ways. Theallotetraploids of B.rapa chinensis var. utilis×B.oleracea var. italica and B.rapa chinensis var.utilis×B.oleracea var. alboglabra had many common features.5. The process of meiosis of the allotetraploid and allotriploid between B.rapa chinensis var. utilis andB.oleracea var. italica was investigated by general cytology methods. Abnormal behaviors ofchromosomes in the process of meiosis were observed, such as chromosomes lagging andchromosomes bridge. The chromosome distribution at anaphase Ⅰwas unbalanced, having15/14,16/13and so on, the separation of15/14had the highest proportion with38.73percent.Chromosomes separated equally or unequally at anaphase Ⅱ and finally produced gametes withdifferent chromosomes.6. The backcross BC1between allotriploid and B.rapa chinensis var. utilis were used as materials inthis study. Two monosomic alien addition lines and one double monosomic alien addition line wereidentified by flow cytometry and karyotype analysis. The monosomic alien addition line namedAA-C6(B.rapa chinensis var. utilis with chromosome6from B.oleracea var. italica) had lightyellow flowers and low fertility, but can produce few seeds by selfing. The monosomic alienaddition line named AA-C8(B.rapa chinensis var. utilis with chromosome8from B.oleracea var.italica) had yellow flowers and fertile. The double monosomic alien addition line named AA-C4-C7(B.rapa chinensis var. utilis with chromosome4and chromosome7from B.oleracea var. italica)had light yellow flowers and sterile.