Climate change-induced events are causing salinization of many rice-growing areas, requiring the identification of new sources of genetic variation for salt tolerance in plant genetic resources since commonly grown cultivars are sensitive to salt. To identify the level of salt tolerance across a wide range of genotypes, we used a multivariate screening method using multiple growth and physiological traits simultaneously. For this purpose, four indica, two japonica and two wild rice genotypes were grown hydroponically under 40 and 80 mM NaCl stresses; fourteen different growth, qualitative and physiological traits, e.g. plant height, biomass, root and shoot elongation rates, and tissue ion accumulation, were recorded. In general, indica varieties performed better than both japonica and wild species. Our approach identified the existence of qualitatively different mechanisms of salt tolerance across the genotypes. For example, Pokkali, a salt-tolerant indica variety, displayed both ‘Na exclusion’ and ‘ion balance’ mechanisms, whereas PSBRc50 and IR58 showed only ‘Na exclusion’, and the Japonica genotypes Banikat and Nipponbare showed only ‘ion balance’. The results demonstrated that the tolerance is dependent on the level of stress and that this varies between genotypes; Nipponbare is moderately tolerant to 40 mM NaCl but not to 80 mM. We also suggest that the use of multivariate analyses can simplify the complex salinity tolerance picture and can effectively reveal the salinity tolerant genotype from a wide range of germplasm. The results reported here identify different physiological mechanism of tolerance across the genotypes and provide a sound basis for future studies examining their underlying molecular mechanisms.

The main goal of the Tera Watt A Cumulator project (Institute for Theoretical and Experimental Physics, Moscow) is accumulation in the storage ring of an intense ion beam, its longitudinal compression and the use of the extracted beam for plasma experiments. However, beam parameters at the target are decreased because of extreme transverse heating and growth of the beam momentum spread due to intrabeam scattering. These effects can be suppressed by application of the electron cooling system (ECS). Design study of ECS has been performed in the Joint Institute for Nuclear Research. The design project and characteristics of the system are described, as well as analysis of the accumulation kinetics in the presence of the cooling system. Design work has shown that because of the small length of the straight section (2.35 m), the effective length of the cooling system is small (about 55–60 cm). Nevertheless, for long accumulation times (>100 s), the system allows us to significantly improve the beam parameters at the target (specific energy, specific power, and so on) and to suppress the beam losses by an order of magnitude.

Variation for K+ and Na+ accumulation at low salinities in hydroponic (water) culture were observed in shoots of different wheat species. Greater discrimination (in favour of K+ and against Na+ accumulation) was shown by hexaploid bread wheat (Triticum aestivum L.) than by tetraploid durum wheat (T. turgidum L.). Since Aegilops tauschii Cosson (A. squarrosa L.), the source of the D genome in bread wheat, also exhibited high discrimination between K+ and Na+, it was concluded that the character resided in the D genome. Studies of aneuploid bread wheat lines and disomic substitution lines of D genome chromosomes for their A and B genome homoeologues in durum wheat cv. Langdon revealed that the trait was controlled by the long arm of chromosome 4D. Since the aneuploid and disomic substitution lines showed better relative salt tolerance than durum wheat, but had lower yield potentials, we recombined chromosome 4D with chromosome 4B in a tetraploid wheat background using a homoeologous pairing mutant. This produced families of 4D/4B recombinant lines, some of which exhibited the enhanced K+/Na+ discrimination trait. RFLP analysis confirmed that the trait was controlled by a single gene (Kna1) which was completely linked to five markers on the distal third of the long arm of 4D. A second cycle of homoeologous recombination was employed to remove the distal 4D genetic material from the recombined Kna1 4B/4D chromosome and to map Kna1 in greater detail. By this strategy, Kna1 was mapped within a short 2 cM region. Genetic analysis of K+[ratio ]Na+ ratios showed very high LOD scores in this region for plants grown in solution culture, but lower values for plants grown in the field.

In general, recombinant lines which exhibited the enhanced K+/Na+ trait were slightly more tolerant of salinity in the field and in sand culture than recombinants lacking the trait. There was, however, considerable variation between individual lines. Ion discrimination and relative tolerance were also higher in a Kna1 recombinant (line no. R3) than in a kna1 recombinant (line no. R165) in sodic conditions. In these two lines the enhanced K+/Na+ discrimination trait did not alter responses to low potassium or calcium supply.