Oxidative stress indicators, malondialdehyde (MDA) accumulation and chlorophyll retention, were tested as tools for salt‐tolerance screening in Chloris gayana (Kunth), a forage grass exhibiting inter‐ and intra‐cultivar variability in the response to salt stress. Three types of experimental system were compared, salt shock, gradual salt treatment and leaf segments floated on control and saline solutions. Results followed the same trend in the three systems, but leaf segments or gradually salinized plants are the most convenient. Lower mean MDA and higher mean chlorophyll content were found under salinity in cv. ‘Katambora’, which is considered, from previous field trials, to be more salt tolerant than cv. ‘Boma’. Nevertheless, chlorophyll content did not give consistent results in other tests and it is not recommended for selection purposes. Within cv. ‘Boma’, clones rating higher in a salt tolerance evaluation under greenhouse conditions had lower MDA content under salinity and lower mean MDA ratios between salt‐treated and control samples. The survival of 80‘Boma’ plants under increasing NaCl concentration was assessed and MDA was measured in the leaves of very plant before the final NaCl level was reached, to assess whether it was predictive of survival capability. MDA values were significantly lower in the group surviving longer, thus, a selection based on low MDA values would have enriched the original population with more tolerant individuals.

Rhodes grass (Chloris gayana Kunth) is widely cultivated in the semi-arid tropics and favoured for salt tolerance; nevertheless, productivity decreases significantly under saline conditions, especially in tetraploid cultivars. The purpose of this work was to explore, in the tetraploid cultivar Boma, the physiological causes for such decrease. Experiments were carried out in vegetative plants in the greenhouse. At high salinity (200 mM NaCl), an early reduction in leaf area expansion was observed, and, later, decreased dry matter accumulation, suggesting that the central effect of salinity was a limitation of leaf growth. This was evaluated in 2 closely related Boma clones, exhibiting different degrees of salt tolerance. Growth, ion accumulation and excretion, sugars, and proline concentrations were measured under a range of salt concentrations (0–200 mM NaCl). Differences between the clones in leaf expansion were expressed only at high salinity, but were not associated with differences in water potential or hydraulic conductance in the expanding region. At all salinity levels, the proportion of dry leaves was higher in the clone which also had lower salt gland density and Na excretion rates. Less efficient Na extrusion, associated with high oxidative stress, may be the main cause for leaf senescence and differences in productivity between these clones.

Variability in the response to salinity within Chloris gayana (Rhodes grass) germplasm was evaluated under field conditions, and random amplified polymorphic DNA (RAPD) markers were used to assess genetic relatedness among cultivars/accessions. RAPD analysis showed a clustering of cultivars of known relatedness: cv. Pioneer and accessions Local and Trancas (derived from an old Pioneer pasture established in saline soil) belonged to the same cluster, Katambora to another and tetraploid Boma and Callide could be further separated, Boma belonging to a fourth, distant cluster. Field experiments were laid out in two types of plots: control [with electrical conductivity of the saturation extract (EC) = 3·64 dS m−1] and saline (EC=13·10 dS m−1) and two experiments were carried out: one to evaluate the effects of salinity on emergence and establishment, and the other, with a uniform number of plants per plot, to evaluate yield under saline conditions. All cultivars/accessions had salinity‐associated decreases in dry‐matter (DM) production during the establishment phase. After this stage, 1‐year DM yield was similar in all cultivars within each salinity level and production in the saline plots was significantly lower than in controls only in cv. Callide and accession Trancas. Second‐year production in the non‐saline plots increased by 30% on average over the previous year, whereas an average 40% reduction was observed in the saline plots. Thus, salinity had a negative effect on Rhodes grass establishment and persistence. The cultivars could not be ranked unequivocally by production under saline conditions, but tetraploids Boma and Callide may be said to be less tolerant than the rest on the basis of an increased proportion of dead leaves and decreased number of stolons observed in the saline plot.

The Argentinean semiarid Chaco region is climatically suitable for cattle raising and has an average annual rainfall of 550 mm, concentrated from November to February. There, large areas are affected by high salinity; thus, perennial forages suitable for this region must combine adequate salt and drought tolerance. Panicum coloratum is a C4 perennial grass adapted over a wide range of soil and rainfall conditions, and the purpose of this study was to evaluate the response of two cultivars (Klein Verde and Bambatsi) to salinity. Under controlled conditions, 100 and 200 mmol l−1 NaCl delayed germination and significantly reduced germination percentages and seedling survival in both cultivars. However, in the field, factors other than salinity (possibly drought) had a large impact on plant survival. In short‐term experiments under controlled environmental conditions, the vegetative growth of cultivar Klein Verde was less affected by salinity than Bambatsi. The cumulative growth over one year in a saline plot was also higher in cultivar Klein Verde. This cultivar also had higher shoot K+/Na+ ratios under salinity, as a result of higher K+ concentrations, and accumulated more triglycerides in roots. These features have been associated with salt tolerance in other species.

Branched nodal roots comprise the largest portion of the root system mass in Chloris gayana Kunth and the effects of high salinity on nodal root appearance and elongation rates were analysed in cv. Boma in greenhouse experiments. Roots from salt‐treated plants (0·2 mol l–1 NaCl) were smaller than controls, and accumulated higher concentrations of soluble sugars and reserve lipids. The number of nodal roots was reduced by the saline treatment. Leaf, tiller and nodal root appearance were delayed by salinity but the correlation among these processes was maintained, indicating that the developmental pattern was not altered by this level of salinity, only its rate. Initial nodal root growth rates varied as a function of plant size and were decreased by salinity only after 2 weeks of treatment. When shoots of non‐salinized plants were cut, a drastic reduction in nodal root appearance was observed, suggesting emerging leaves were stronger sinks than roots for available reserves. However, when the shoots of salt‐treated plants were cut, the already depressed root appearance rate was not further reduced. This suggests that, under salinity, alterations in root ability to metabolize reserves could have been more significant than reserve availability for controlling elongation.