Riaz Hussain Qureshi

A rapid screening technique for salt tolerance in rice (Oryza sativa L.)

An effecient, reproducible and simple mass screening technique for the selection of salt tolerant rice lines has been developed. Fourteen-day old seedlings raised in silica gravel culture were transplanted to foam-plugged holes in polystyrene (thermopal) sheets floated over 100 dm3 of nutrient solution in painted galvanised-iron growth tanks lined with plastic (120×90×30cm). Three days after transplanting, NaCl was added to salinize the medium in increments, at the rate of 25 mol m-3 per 24 hours, up to the desired salinity levels which ranged from 50–200 mol m-3 NaCl. Six plants of each line were transplanted and allowed to grow for 15 days after the maximum desired stress level was achieved in each case. Absolute shoot fresh and dry weights, as well as percent mortality, were used as criteria for assessing relative salt tolerance. Related studies were also conducted to standardize the technique. The validity of this technique was tested by conducting experiments in salinised soil (pot culture) and in salt-affected field where 9 rice lines were grown up to maturity and absolute paddy yield was considered as the criterion for salt tolerance. Salt tolerance behaviour of cultivars based on different selection criteria was compared. Good reproducibility of results among the three solution culture experiments and their close association with the results of pot culture and of salt-affected field study, authenticated the validity of this technique for practical purposes.

COMBINED EFFECT OF SALINITY AND HYPOXIA IN WHEAT (TRITICUM AESITIVUM L.) AND WHEAT-THINOPYRUM AMPHIPLOIDS

The effects of sodium chloride salinity and hypoxia were studied in eight wheat lines and three wheat-Thinopyrum amphiploids in vermiculite-gravel culture. The lines were treated with either 100 or 150 mol m−3 NaCl with and without hypoxia. Saline hypoxic conditions significantly reduced the vegetative growth, water use, grain and straw yields for all wheat varieties except the amphiploids, whereas NaCl or hypoxia alone had less pronounced effects. In addition, saline hypoxic stress reduced K+ concentration and increased significantly the Na+ and Cl− concentrations in cell sap expressed from leaves. There was more Na+ and Cl− accumulation in wheats than the amphiploids in hypoxic conditions at 150 mol m−3 NaCl. Of the wheats, Pato was the most sensitive at all stress levels while aTriticum aestivum cv. Chinese Spring ×Thinopyrum elongatum amphiploid was the most tolerant of the three amphiploids.

Horizontal flushing: a promising ameliorative technology for hard saline-sodic and sodic soils

Abstract Highly dispersed hard saline-sodic soils are very important agricultural soils in Pakistan and elsewhere in the world. These soils are almost impermeable to infiltrating water. Conventional reclamation procedures using gypsum amendment followed by vertical leaching (GVL) resulted in uneconomical returns from these soils. A technique was developed and evaluated that involved mixing of gypsum with the soil in standing water with a cultivator followed by horizontal flushing of the standing water from the soil surface to a nearby drain and a second flushing repeated after 12 h (GFF). Rice production responded positively to the GFF technology compared to the conventional GVL practice. However, the differences for wheat production and soil reclamation were not so prominent. In a second field experiment, the GFF technique was modified by applying gypsum in between the two water flushings (FGF) and compared to the above mentioned treatments, with (GVL and GFF) or without gypsum (VL and FF). The FGF treatment produced superior results both in terms of soil salinity–sodicity amelioration and crop production.

GENOTYPIC VARIATIONS OF PHOSPHORUS UTILIZATION EFFICIENCY OF CROPS

Intra-specific variations of phosphorus-utilization efficiency (PUE) hold great promise in rationalizing the application of cost-intensive phosphatic fertilizers in resource-poor situations, and to extend the useful life of the phosphate reserves in the world. In developed countries, efficient P-using crops may find significance in protecting the environment by reducing pollution of surface and ground water resources. This paper briefly reviews some of the work done so far on genotypic variations of Phosphorus (P)-nutrition of crops. Several physiological mechanisms responsible for such variations have been recognized. Various screening techniques to select P-efficient genotypes are also discussed. In addition, a brief historical account is also given on plant genetic approach to tackle soil problems.

Performance of selected tree species under saline-sodic field conditions in Pakistan

Results are reported regarding four preliminary and two long-term field studies on the performance of selected (number varies from one to 12 in different studies) tree species under saline-sodic conditions. The surface salinity (0-30cm) of soil in the long term studies at Uchkera farm varied between 15 and 41dS m-1, SAR between 13 and 172, and, in general, it decreased with increase in soil depth. The plants were planted in furrow beds irrigated with fresh canal water and soil below furrows had lower EC e and SAR values. At PARS site, surface EC e, varied from 17.6 to 83.8 dS m-1 and SAR between 38.4 and 129.5 and it decreased with increase in depth. The soil at Uchkera farm was light textured whereas at PARS it was dense. On overall basis, Eucalyptus camaldulensis proved to be the most successful species under a variety of salinity conditions while Leucaena leucocephala was the most aggressive species especially under moderate salinity conditions. Tamarix aphylla showed rapid growth under high salinity.

Phosphorus nutrition of cotton cultivars under deficient and adequate levels in solution culture

In low-input agricultural systems that characterize most of the developing world, nutrient-efficient crop cultivars may play significant role in improving crop productivity. Phosphorus (P) deficiency is a common phenomenon in cotton growing areas of Pakistan, however the farmers are reluctant to apply it due to its price and fear of lack of response. A solution culture experiment was conducted to evaluate 10 commonly grown cotton cultivars for their relative efficiency to utilize deficiently and adequately supplied P, using Johnsons solution. Phosphorus deficiency markedly reduced shoot dry weight (SDW), root dry weight (RDW), whole plant dry weight controlled by plant P contents under P deficient conditions, suggesting an internal regulation in addition to the influence exerted by external P supply. The conclusions from experiment were that differences in growth existed among cotton cultivars exposed to same P concentration in the growth medium. Cultivars, which were efficient in both P-acquisition and P-utilization, were efficient accumulators of biomass under adequate as well as deficient level of P supply.

Does tolerance of wheat to salinity and hypoxia correlate with root dehydrogenase activities or aerenchyma formation

The effects of NaCl salinity (100 or 150 mol m-3) and hypoxia on seedlings of several wheat varieties (Lyallpur-90, SARC-1, Pato, Tchere, Pb-85, Siete Cerros, Chinese Spring and a Chinese Spring × Thinopyrum elongatum amphidiploid) were studied in solution culture. In vivo studies of activities of different enzymes (alcohol dehydrogenase (ADH), lactate dehydrogenase (LDH) and cytochrome oxidase (COase)) extracted from Pato and Pb-85 included the effect of salinity with and without hypoxia, while during in vitro studies, NaCl, glycinebetaine and proline were added to the assay mixture. The extent of aerenchyma formation was also determined in Pato, Chinese Spring and a Chinese Spring × Thinopyrum elongatum amphidiploid. Imposition of hypoxia greatly induced ADH and LDH activity in roots of wheat seedlings after a week-long exposure. However, exposure of roots to salinity also slightly increased LDH and ADH activity compared with the non-saline control. On a relative basis, Pato had higher ADH activity under hypoxic (21×) or saline-hypoxic stress (20×) than in aerated conditions. Hypoxia alone or in the presence of salts decreased COase activity in both Pato and Pb-85. The in vitro studies revealed that NaCl (on an equimolar basis at up to 500 mol m-3) is more disruptive than glycinebetaine or proline. LDH was more sensitive to NaCl than ADH. Aerenchyma development was higher near the root-shoot interface compared to near the root tip. Salinity under hypoxic conditions significantly reduced aerenchyma development near the root tip and root-shoot interface compared to hypoxia alone. Neither enzyme activity nor aerenchyma formation could account for varietal differences in tolerance to hypoxia alone or in combination with salinity.

Calcium and salt-tolerance of rice

The impact of calcium (Ca) supply on the growth and yield of rice was studied in nutrient and soil culture experiments. In solution culture experiment, the effect of external‐Ca supply (0.5, 1.0, 1.5, 2.0, 3.0, 4.0 mM Ca) on the growth and shoot composition of two rice cultivars, varying in salt‐tolerance, in the presence and absence of 100 mol m− 3 NaCl was measured in a four week trial. In soil culture experiment, Ca (as gypsum; CaSO4 · 2H2O) was applied at the rates of 0, 10, 25, 50 and 100% of gypsum requirement (GR) of the saline‐sodic soil (after determining its GR). A positive, improving and stimulative effect of Ca was noted in growth characteristics (shoot and root weight and tillering capacity) in both the cultivars at 1.0 to 1.5 mM Ca; above this concentration, Ca had inhibitory effect. Although increasing supply of Ca tended to decrease sodium (Na) and chloride (Cl) concentration in the shoots of both rice cultivars, shoot‐concentrations of Na and Cl were much lower in NIAB‐6 (salt tolerant) than IR 1561 (salt sensitive). An increase in potassium(K):Na ratio, an indication of salt tolerance, was observed at 1.0 mM Ca and above in both rice cultivars under saline environment. Result, confirmed in salt affected soils of two different types (saline and saline sodic), showed an improvement in the paddy yield of both salt tolerant and salt sensitive rice cultivars due to Ca application as gypsum at the rate of 25% of GR of soil. Excessive rates of Ca either in solution culture or soil were detrimental for plant growth and paddy yield. The ameliorative effect of Ca was because of increased Ca:Na ratio of the growth medium.

Different Eucalyptus Species Show Different Mechanisms of Tolerance to Salinity and Salinity × Hypoxia

ABSTRACT We studied the effect of sodium chloride (NaCl) salinity and oxygen deficiency stress on growth and leaf ionic composition of three Eucalyptus species [E. tereticornis, E. camaldulensis (Silverton), and E. camaldulensis (Local)]. Species were grown with control (no NaCl) and salinity (150 mol m−3 NaCl) under hypoxic and non-hypoxic conditions in nutrient solution with five replications following CRD. Species differed significantly in their response to salinity and hypoxia. Absolute shoot dry matter was significantly better in E. camaldulensis (Silverton) in salinity and in E. camaldulensis (Local) in saline hypoxic treatment. E. tereticornis was the most sensitive species to salinity and salinity × hypoxia in the root environment. Sodium (Na+) and chloride (Cl−) concentrations were significantly lower in E. camaldulensis (Local) in non-hypoxic saline treatment compared to the other two species. E. camaldulensis (Silverton) seems to have better tissue compartmentalization, whereas E. camaldulensis (local) seems to have better exclusion of Na+ at the root level.

Effect of saline soil on grain quality of rices differing in salinity tolerance

Four varieties of rice, differing in salinity tolerance and grown in saline soil (electrical conductivity 5–6 dS/m) at Sadhoke, Punjab, Pakistan, had lighter grain and higher Na content than control samples. Grains of three out of the four rices grown on saline soils had higher brown rice protein (higher nutritional value), less translucent grain, lower starch and amylose content, and lower K than their control samples, but these differences were not related to salinity tolerance. Alkali spreading value and gel consistency were not affected by culture in saline soil. Cooked rice Instron hardness increased in saline culture in two higher-protein samples of the four rices. Amylograph peak viscosity was suppressed by saline culture.