Abstract
Increased production of sugar beet under rainfed conditions on saline–sodic soils in the Iranian areas highlights the importance of salt tolerant varieties. Screening of genotypes for salinity tolerance is difficult in field due to heterogeneity of physical and chemical properties of soil. In order to evaluate the salinity tolerance of 21 sugar beet monogerm O-types lines, a pot experiment was conducted using a split plot design. The evaluation of plants was performed using 11 morphological and physiological traits at vegetative growth stage under severe salt stress (∼16 dS m-1) and control (0.3 dS m-1) for 8 weeks. Salinity stress significantly reduced weight related traits. The response of genotypes for total weights and stem weights was very similar under both conditions. But, ranking of O-type lines for root weights under normal and stress condition was different. Indeed, there was high significant genotype × treat interaction for two these traits. Cluster analysis by using STI index of all traits allowed the identification of tolerant, moderate tolerant and sensitive genotypes toward salinity. The four salt-tolerant genotypes, O-type 9669, O-type 1609, O-type 463-2, and O-type 463-5 identified in this study, could be used in the development of salt-tolerant sugar beet varieties. In the second part of this study in order to assess a simple, rapid, and nondestructive method to estimate chlorophyll content, the chlorophyll meter (SPAD 502) readings were recorded and the relation was determined. Regression analysis indicated that there was a signiï¬cant linear regression between chlorophyll content and chlorophyll meter and about 74% of changes in chlorophyll meter based on chlorophyll content were predicted. Key words: Sugar beet (beta vulgaris L.), salt tolerant index, screening, hybrid.
Highlights
Threats to the 21st Century include depletion of water resources, environmental contamination, and excessive salinity of soil and water
The fresh weight was measured for shoot (SFW), root (RFW) and total fresh weight plant (TFW)
The phenomenon of necrotic appeared in plant leaves, but only salt tolerant genotypes were able to maintain their biomass and photosynthesis and able to overcome salt stress. These results indicated the existence of genetic potential for salt tolerance among this sugar beet O-type lines that could maintain a good growth status in plant aerial part under salt stress and show that stress intensity (16 dS/m) used in our study, was appropriate which was able to differentiate between susceptible and tolerant controls, and to differentiate genotypes for different traits
Summary
Threats to the 21st Century include depletion of water resources, environmental contamination, and excessive salinity of soil and water. The increased production of sugar beet under. Compared to other crops, sugar beet is comparatively tolerant to abiotic stress conditions, owing to Beta vulgaris sp. Maritima as the wild progenitor of sugar beet, which prospered insuch harsh conditions (Ober and Rajabi, 2010). The selection for improving stress tolerance in seedling stage ameliorates plant establishment in the field (McGrath et al, 2008). It is necessary for the majority of sugar beet breeding programs to focus on increasing germination and establishment in saline environments in order to maintain crop productivity. Most studies screening genetic sources under salt conditions have been accomplished in controlled environments with a single level of salt stress and no validation of the results under field conditions
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