| Development and use of the vegetable varieties with salinity tolerance will increase the utilization of the saline soil distributing in arable land and the productivity of vegetables, improve the entironment on farmland, enrich the vegetable diversity in saline area. Studies on the genetics and gene expression of salinity tolerance in Pak-choi [.Brassica campestris L. ssp. chinensis (L.) Makino var. communis Tsen et Lee.] under salt stress were carried out in order to understand the mechanism of salinity tolerance in plant, mine the related genes of salinity tolerance, and use heterosis or molecular breeding to enhance the salinity tolerance in vegetables.Genetics of salinity tolerance in Pak-choi was investigated by a eight-parent complete diallel cross II design only including direct crosses. Combining ablity and genetic component analysis were estimated by using Griffingll and Hayman methods. Estimate of combining ability for salinity tolerance showed there were highly significant differences in GCA and SCA. Estimates of GCA and SCA effects of different varieties or combinations showed that not noly the parents with high GCA could produce good F! with high SCA, but also the parents with poor GCA could produce good combinations with high SCA. Inheritance of salinity tolerance in Pak-choi fitted to the "additive-dominant" model. There were additive effect and dominant effect in genetic effects. However, the dominant effect played a major role and overdominance may exist in salinity tolerance exhibition. Salinity tolerance was mainly controlled by dominant genes and salinity sensitively was controlled by recessive genes. Inheritances of salinity tolerance may be controlled by few major genes under the regulation of other genes. Selection should be focused on both the parents with high GCA and the higher SCA combinations in heterosis breeding on salinity tolerance improvement in Pak-choi.The salinity tolerance related genes expression under salt stress of certain intervals and different salt levels in two varieties was studied with two primer combinations by DDRT-PCR. Expression intensity under 1.6% NaCl were stronger than that under 1.2% and 2.0% NaCl. Expression reached the highest level for 6h salt stress. Expression level was less at 12h than 6h. But expression increased with the time under stress from 12h. It tended to be steady at 48h. It decreased after 72h. It was suitable to study the differential expression of the salinity tolerance related genes in Pak-choi for 48h under 1.6%NaCl stress. These results above would help us know the procedure and characteristics of the expression of the salinity tolerance related genes, and make effective stratege for salinity tolerance study in Pak-choi.The mRNA differential display was used to show the differential expression among the two salt-tolerant, one moderate salt-tolerant and one salt-sensitive parents and their four kinds of F1: tolerant tolerant, tolerant x moderate tolerant, sensitive x sensitive and tolerant x sensitive under 1.6%NaCl stress and non-salt stress. Fifteen primer combinations generated 116 differential cDNA fragments in 2512 cDNA fragments in total. Significant differences of gene expression among the parents and Ft were observed under salt stress. These differences were related to the phenomena of salinity tolerance. The results helped us understand the heterosis theoretically and guide the heterosis breeding.The mRNA differential display was used to screen the related transcriptic drived fragments of salt tolerance in salt-tolerant and moderate salt-tolerant varieties under the 1.6% salt stress and non-salt stress. Seven-eight primer combinations generated 101 differential cDNA fragments which were divided into 10 expression types. After they were proved to be positive by repeated PCR and northern blotting, thirteen cDNA fragments were reamplified by PCR, cloned and sequenced. Seven cDNA sequences were gained. BLAST analysis from GenBank and Brassica datebase found cDNA fragment 38 and 68 were 90% and 95% homologous to the expression genes i...
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