Study On The Salinity Resistance And Resistance Gene Expression In Cotton Germplasm

Salinity resistance and differential gene expression associated with salinity in cotton germplasm were studied, according to the large scale of saline area in China and its negative significant effects on the cotton production. The pedigree and correlation coefficients between agronomic traits and the salinity tolerance were analyzed from 60 salinity tolerant cotton genetypes. The tolerance and its biochemical effects on the main genetic characters, the resistance genes and their differential expression were studied by the salinity-tolerant and salinity-sensitive cotton genetypes. The following were the results:1. The basic germplasm and its pedigree were explicitly clarified. The genealogy of 60 cotton salinity-tolerant genetypes was clustered into four basic germplasms such as Deltapine, King,Uganda and Russia, whose descents were contributed to the most of the salinity-tolerant cotton varieties. According to the genealogy proportions, there were 88.33% of Deltapine, 81.67% of Uganda,78.33%of King, and 65% of Russia in all of the 60 salinity-tolerant cotton varieties. All the main cotton varieties, nowadays, at the much lower level of salinity-resistance, are due to the two reasons. The one is the much lower level of salinity-resistance of the basic germplasm, and another is that the basic germplasms are extremely too centralized to broaden the background of the salinity-resisted cotton varieties.2. The correlations of the salinity resistance with the main genetic characters were analyzed. The salinity resistance positively correlated with the boll weight outside of the main cotton agronomic characters under the stress of NaCl. As to the relationships between the salinity resistance and the seed quality, the salinity resistance negatively correlated significantly with the protein proportions and positively correlated significantly with fat of the cotton seed embryo. There were remarkable relationships between the salinity resistance and the fiber quality. The salinity resistance positively correlated significantly with the fiber length and negatively correlated significantly with the fiber micronaire, which indicated that salt stress could enhance the elongation and inhibited the thickness of the fiber. The results also indicated that there were positive correlation between the salinity resistance and the draught resistance, which showed that the mechanism of salinity resistance was similar to that of the draught resistance.3. The effects of salinity stress on the cell division and chromosome behavior were first observed on cotton. It could be obviously observed that there were negative, at the lower(0.1%-0.2%) NaCl, or positive, at the higher concentration (0.3%-0.5%) of NaCl, effects on the mitosis index of the cotton seedling, The effects of NaCl changed with the resistance level of the varieties. The abnormal chromosome behavior such as C-mitosis, Chromosome bridge, Chromosome stickiness, Chromosome melting had been observed and first studied in detail on cotton. All the abnormal behaviors fluctuated with the salinity resistance of cotton and the concentration of NaCl.4. Metabolism changes of total protein, soluble sugar, and physiological characters of SOD(superoxide dismutase) ,POD(perioxidase) activity under the NaCl stress were studied. There were negatively correlation between the salinity resistance and the leaf membrance injury. POD and SOD activities changed higher as the NaCl changed to higher concentrations, but SOD activity of the salinity-resisted cotton fluctuated quickly than the salinity-sensitive cotton, and it was on the reverse of the POD. The protein proportions reduced significantly as the NaCl concentrations got to higher with the novel proteins such as 80kD, 36kD, 26kD, 24kD of the salinity-sensitive cotton. The results showed that there were 80kD and 36kD proteins of the salinity-resisted cotton under the stress of NaCl. The results also showed that 24kD, 36kD were correlated with the salt resistance of plants and 26kD was similar to the osmotin. 80kD was the first found protein as to the mechanism of the cotton salinity resistance.5. The salinity-resisted genes and their differential expression were studied under the stress of NaCl on cotton. There found, under the NaCl stress, 1644 genes differentially expressed from the salinity-sensitive cotton and only 817genes differentially expressed from the salinity-resisted cotton. The differential expressed genes could be divided into five groups according to the expressed levels by the cluster analysis. A goup:32 up-conditioned genes, differentially expressed only in the salinity-resisted cotton; B group, 548 up-conditioned genes, differentially expressed only in the salinity-sensitive cotton; C group, 176 down-conditioned genes, differentially expressed only in the salinity-resisted cotton; D group, 487 up-conditioned genes, differentially expressed only in the salinity-sensitive cotton; E group, 609 down-conditioned genes, differentially expressed both in the salinity-sensitive and salinity-sensitive cotton. The salinity-resisted differentially genes could also divided into 4 groups according to the known functions of the expressed protein: 96 osmotin genes, 48 toxicity-reduced genes, 136 transcription factors, and 98 signal transmitted genes.