Genetic Analyses On Brassica Napus×Sinapis Arvensis,Brassica Rapa×Orychophragmus Violaceus Hybrids And Their Progenies

The wide hybridizations can break limits of species in some extent, promote genetic introgression and communication of different species, which are effective approaches to transfer useful characters to cultivated crops, to produce new species, to introduce alien gene and create variations. At present by this breeding method, a lots of important and special genes have been transferred to Brassica crops from wild relatives. The wide hybridization is also one of methods in plant cytogenetics and breeding to observe new chromosome behavior in successive generations, and to enrich contents of cytogenetics. Up to now, the particular chromosome behaviors, such as chromosome doubling, formation of unreduced gametes, chromosome elimination and separation of parental genomes, have been reported in plant wide crosses. Intergeneric somatic and sexual hybrids coveting Brassica napus and Sinapis arvensis have been reported, but no cytology given. In this investigation, the intergeneric hybrids between B. napus and Xinjiang wild rapeseed, one ecological type of S. arvensis were obtained through embryo rescue and their chromosomal / genomic compositions analyzed by the methods of cytogenetics and amplified fragments length polymorphism (AFLP), to observe their evolution relationships and chromosome elimination and introgression in wild hybridizations. In addition, genetic analyses were made on F₁₁ inbred lines from hybrids between B. rapa and Orychophragmus violaceus. The results were described as follows.1,Production and morphology of intergeneric hybrids between Brassica napus and Sinapis arvensis. After a lots of hand emasculation and pollination with B. napus as female and S. arvensis as male, 119 embryos were obtained and cultured on MS medium. The plantlets from 8 embryos were distinguished from the others by showing different phenotypes from B. napus parent and some traits of S. arvensis. The 8 putative hybrids were further confirmed by their deviated morphology at different growth stages in field. All F₁ plants showed the similar morphological traits at early stage, such as intermediate leaves between those of their parents. Their basal leaves were fully divided with one to three pairs of small lobes, and show trichomes on both sides and on the petioles. But some difference in phenotypes was presented in the adult plants. 2,Cytology of hybrids and progenies. The somatic cells in young leaves of plantlets on medium and ovaries of flower buds had the the same chromosome numbers, 2n=29, not the expected 2n=28. In all F₁ plant derived from the eight embryos, pollen mother cells (PMCs) mainly had 11â…¡+7â… at diakinesis and showed the 14:15,13: 16,12: 17,11:18 segregations at anaphaseâ… (Aâ… ) with 14:15 being most frequent. In some Aâ… PMCs, lagging chromosomes appeared. No S. arvensis chromosomes were detected by GISH analysis.F₂ plants and backcross plants to B. napus had the similar morphological traits to F₁ plants and showed low fertility by producing pods with only 2-4 seeds. Their ovary cells had different chromosome number.3,AFLP fingerprint analysis. Sixteen pairs of AFLP primes were randomly selected and used for AFLP fingerprint analyses. Totally, 288 polymorphic bands were generated, among which 89 bands were specific for Brassic napus, 88 for S. arvensis, 18 common for two parents, indicating their distant relationships.4,The F₁₁ inbred lines from Brassica rapa cv. "Aijuehuang"×Orychophragmus violaceus crosses showed wide variations in morphology among lines. Some plants exhibited purple color on leaves,petioles,stemes,siliquaes and basal clustering branches which from O. violaceus more or less. Each line had different chromosome numbers with 2n=36-40, and 2n=38 was most frequent, but no intact chromosomes of O. violaceus origin were included. Using seventeen pairs of AFLP primes randomly selected, AFLP analyses revealed a high extent of variation in genomic compositions across all the lines, and O. violaceus-specific bands, deleted bands in B. rapa and novel bands for two parents were detected with novel bands being most frequent.Finally the mechanisms about the formation of these intergeneric hybrids, the interaction between different genomes, chromosome elimination and genetic introgression in wild hybridizations were discussed.