The Salt Tolerance Classification Of Transgenic Insect Resistant Cotton Varieties And The Study On Soaking Seed With Glycinebetaine On The Salt Tolerance Of Cotton Seedlings

Cotton is a main agricultural product in the world and salty soils have a tremendous impact on farmers'livelihood. Finding ways to increase salt tolerance of cotton is crucial in agriculture. The article aimed at the important problems demanding prompt solution to forming seedlings of cotton in saline-alkali soil, we solved this problem by studying the salt tolerance classification of 15 transgenic insect resistant cotton cultivars and the salt tolerant mechanism of seedling. It was expounded the index of salt tolerance classification of variety types of cotton at germination stage, and the effects of salt stress on seedlings at cotton germination and seedling stage And then the mechanisms of seed soaking with glycinebetaine to elevate salt tolerance of cotton seedlings was studied.The experiment was conducted in the room and the scientific farm of Shandong agricultural university from 2005 to 2007. 15 transgenic insect resistant cotton cultivars were used in these tests to classify salt tolerance types. Making use of the methods of pot culture and germinating box were conducted to study on the effects of salt tolerance at germination stage and soaking seed with glycinebetaine on the salt tolerance of cotton seedlings, with two varieties of 99B and LMY28 selected from the first test. The main results were shown as follows:1. The evaluation of salt tolerance indices and classification of variety types of transgenic insect resistant cotton cultivars at germination stage5 indices of germination were investigated of cotton at germination stage which were planted in the room of culture seedling under the salinity condition that 4 salt concentrations was regulated. Correlation analysis, stepwise regression analysis and clustering analysis were madden to find the relations among slat tolerance coefficients. The results showed that slat tolerance coefficient of vitality index play an importance part of salt tolerance classification at gernination stage. There were significant correlation between the index of salt tolerance of vitality index(Y) and that of the hypocotyls length(X1), dry weight(X2), germination percentage(X3) and germination index(X4), equation of multiple regressions at 0.8% and 1.2% salt concentrations were described Y= - 0.523 - 0.053X1+0.468X2 -0.074X3+1.325X4(R2=0.988)and Y=-0.030X1+0.174X2+0.021X3+0.714X4-0.117(R2=0.996), respectively. Comprehensive analysis indicated that three cultivars LMY20, LMY28 and ZMS41 appeared in higher salt-tolerance, jarless agronomic characters; 99B, LMY27, 98-4, LMY23 and H963 also appeared in low-tolerance, better agronomic characters, it offered academic thereunder for selecting seed in saline-alkali soil.2. Study on the salt tolerant mechanism at germination and seedling stageTwo selected transgenic insect resistant cotton cultivars 99B and LMY28 were used in these tests and 3 treatments of salt concentrations water (0.4%, 0.8% and 1.2%) were applied to culture cotton in the room of culture seedling. The result indicated that all the treatments restrained germination of 99B; it improved germination in 0.4% salt concentrations and restrained germination in higher salt-tolerance of LMY28. It restrained seedling growth at germination and seedling stage under all the treatments.The content of synthesis of chlorophyll decreased under salt tress, and with further increasing salt stress, the ranges of decrease were enhanced. The value of Chla/b, actual quantum efficiency (φPSⅡ), photosynthetic electron transport rate (ETR) and NPQ were raised under 0.4% salt concentrations and reduced in high- tolerance. There was an obvious improvement of salt stress on the chlorophyll fluorescence dynamic parameters Fv/Fm, Fv/F0 of LMY28, but no obvious effect on the chlorophyll fluorescence dynamic parameters Fv/Fm, Fv/F0 of 99B. The soluble sugar content in cotyledons and hypocotyls, the proline content in cotyledons was also increased under salt stress, and with further increasing salt stress, the ranges of increase were enhanced. SOD activity was increase under salt stress in cotyledons at cotyledon stage and only one leaf stage, and with further increasing salt stress, the ranges of increase were enhanced. The activities of POD, CAT raised stepwise with the enhancing of salt stress at germination and seedling stage. The soluble protein content of cotyledon was also promoted under salt stress at cotton germination and seedling stage. Two cotton cultivars had the same reaction trend.3. Study on Soaking Seed with Glycinebetaine on the Salt Tolerance of Cotton germination and seedling stageGlycinebetaine (GB) is an amino-acid derivative accumulated in certain plants under water stress, which has been studied as an osmoprotectant in the adaptation to water, salt and cold stress. The adaptation varies with and depends on numerous factors including types of crop, timing and rate of fertilizer application, and environmental conditions. Exogenous GB may help to reduce the negative effects of salt stress in cotton seedling. Two cultivars 99B and LMY28 soaked with 0, 200,400, 600, 800μg mL-1GB for 15 h were used in these tests,and then cultured with water containing 0.6% NaCl in the room of culture seedling. The results indicated that with further increasing GB concentration of soaking seed, germinating energy, germination index, vitality index and hypocotyls length tended to first rising and then reducing under salt stress, it appeared to reach maximum index when 600μg mL-1 GB, soaking seed with GB had more influence on 99B than LMY28 at germination stage. Soaking seed with GB promoted the fresh weight of root and hypocotyl and cotyledon, the area of cotyledon, the number of branch root, the root activity, the content water in cotyledon, the proline content and the activities of protective enzymes SOD, POD, CAT of cotton cotyledon under salt stress. Furthermore, with further increasing GB concentration, they all tended to first rising and then reducing at cotyledon stage. Seed soaking with GB decreased the length of main root, SLW and WSD of cotyledon, the water potential, the soluble protein content of cotton cotyledon at salt stress condition. Furthermore, with further increasing GB concentration, they all tended to first reducing and then rising at cotyledon stage. It also all appeared to reach apex index when 600μg mL-1 GB. Two cotton cultivars had the same reaction trend.4. Effects of soaking seed with glycinebetaine on the salt tolerance of cotton seedlingsThe objective of this study is to determine the effects of soaking seed with GB on the salt tolerance of cotton seedlings whether under salt stress or not. Two cultivars 99B and LMY28 were used in these tests. Some of the seeds of the two cotton cultivars were soaked with 600μg mL-1 GB for 15 h and others with water for 15 h, and then cultured with Hoagland solution or Hoagland solution containing 0.4% NaCl in pots under field conditions. The results indicated that there was an obvious effect of soaking seed with GB on growth and development and physiological characteristics at cotton seedling stage. It promoted the fresh weight of roots, culms and leafs, the leaf area, and the ranges increased were enhanced with further increasing age of seedling. Soaking seed with GB also could promote the synthesis of chlorophyll, but decreased the value of Chla/b; increased the chlorophyll fluorescence dynamic parameters Fv/Fm, Fv/F0, photosynthetic electron transport rate (ETR) and actual quantum efficiency(φPSⅡ), which improved the photosynthetic capacity of cotton seedlings, leafs consequently. In addition, soaking seed with GB also increased the soluble sugar content in leafs and stems of cotton seedlings , increased the proline content in leafs of cotton seedlings,but decreased the relative electrical conductivity of cotyledon, indicating that soaking seed with GB can promote osmotic adjustment ability and alleviate the harm caused by salt stress. Soaking seed with GB also promoted N metabolism through increasing the activity of NR of cotyledon, promoted roots activity and decreased water potential of leafs. Two cotton cultivars had the same reaction trend to GB treatment.