Comparison between sugar beet lines for photosynthesis,respiration and other physiological parameters in salt stress and normal conditions

Increase saline land in the world, limitation of yield increase based on planting area and threat of saline soils and waters for crop production such as sugar beet in most region of world and Iran cause to pay more attention about research related to salt stress and produce tolerant varieties. This study was conducted in order to evaluate sugar beet genotypes based on physiological parameters, as well as to find out these parameters relationship in germination and establishment in greenhouse and field to identify a reliable parameter for discriminating genotypic differences under saline condition. Three separated experiments were done in laboratory (seed germination, identify salt critical electric conductivity), green house (to evaluate suitable planting medium, identify salt critical electric conductivity and study of establishment and physiological parameters) and field (study of physiological and yield parameters). 20 sugar beet genotypes at four salt levels with factorial design in laboratory, 20 and seven genotypes at two salt levels at first and second stages of green house, and nine genotypes at two salt levels with split pot design in the field trial at Rudasht (Esfahan) station during 2007and 2008 were studied respectively. Samplings were taken at two times in each experiment: at the four leaves and establishment growth stages for green house experiment, and leaf development and maturity (harvest time) for the field trial respectively. Seed germination and abnormal plant percentage, radicle and hypocotile length, PSII efficiency, leaf temperature, transpiration, stomata conductance, photosynthesis, chlorophyll a and b content, prolin, protein, H٢O٢, MDA, soluble carbohydrate, inorganic ions, top yield and qualitative and quantitative parameters of sugar beet roots were measured. Finally leaf protein pattern of two tolerant and sensitive genotypes, selected among all experiments, were studied under salt stress (EC= ١٦ ds/m) and normal condition at sugar beet establishment and maturity stages in three replication. IPG stripe gels (١٧cm length, PH ٤-٧) were used for ٢D-electrophoresis with silver staining. The results of this study showed that seed germination was similar in EC=16 and EC=20 dS/m under laboratory conditions, Radicle length and number of abnormal plants were good traits for screening germplasm to salt stress in laboratory. In spite of similar results for EC= 16 and 20 ds/m in laboratory, 50 % seedling losses was observed at EC=16 dS/m in the green house condition. In this condition, seedling growth on Perlit, especially large size, was stronger and more suitable than sand. Sugar beet germination decreased to 35 % and dead seedlings increased to 80 % by growing plants in sand at EC=16 dS/m which shows importance of sugar beet seedling survival till plant establishment in saline condition. The highest effects of salinity were observed at the second growth stages in the green house (establishment) according to photosynthetic characteristics, osmolyte and inorganic ions. So we can select salt tolerant genotypes by planting it in greenhouse and measure suitable parameters during establishment. Leaf potassium, sodium, and their ratio, soluble carbohydrate, phosphorus and leaf proline firstly and leaf chlorophyll, transpiration and nitrogen content secondly were more significant and related characteristics with yield under saline condition during whole growth stages. Salt stress decreased root and white sugar yields significantly in field-Esfahan experiments. Bp Karaj, 7219 p.69, 7233 p.29*MSC2 genotypes had maximum and 452 minimum root, white sugar yields and sugar content percentage among other genotypes respectively. As well, physiological and biochemical parameters of these genotypes grouped them in salt tolerant and sensitive genotypes. Protein pattern showed that among 307 and 218 protein spots detected at establishment and maturity growth stages, 195 and 100 protein spots had significant and repeated changes in two genotypes under salt stress respectively. Salt stress changed protein pattern more in sensitive 452 genotypes than tolerant BP Karaj in the way 167 and 98 protein spot in sensitive genotype, and 165 and 77 spots in tolerant genotype were detected during establishment and maturity stages.13 protein spots responded to salt stress at both growth stages. So we can produce tolerant variety by genetic manipulating of physiological and biochemical parameters related to salt tolerance.