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Effect of Salinity on Growth of Some Modern Rice Cultivars

M.Z. Alam
Adaptive Research Div., BRRI Gazipur

T. Stuchbury
Department of Agriculture & Forestry, University of Aberdeen, UK

R.E.L. Naylor
Department of Agriculture & Forestry, University of Aberdeen, UK

M.A. Rashid
Adaptive Research Div., BRRI Gazipur

Abstract/ Executive Summary:

Ten rice cultivars (Oryza sativa L.) were tested for their salt tolerance at three levels of salinity, 4.5, 8.5 and 12.5 dS m^-1 electrical conductivity (EC) and tap water as control. A 4x10 factorial experiment in split-plot design was used with three replications. Data taken 6 weeks after salt application were reported. Severe effects of salt on rice plant growth were seen even at 4.5 dSm^-1. Growth was arrested immediately after application of 12.5 dS m^-1 salt but not in other lower salt treatments (8.5 and 4.5 dS m^-1). However, with time, salt injury symptoms were clearly visible in all plants growing in all levels of salt and showing different symptoms. The degree of injury was greater in the highest salt concentration (12.5 dS m^-1). The symptoms appeared mostly in older leaves and the upper portion of the leaves rolled in and withered away. The emerging leaf blades were tightly rolled; the tips were severely withered and necrotic. However, the younger leaves of the affected plant remained succulent and looked darker green. The affected plants looked stunted and most of the young tillers gradually died. Salt injury symptoms varied with concentration of salt and between cultivars. The relative salt sensitivity of cultivars was not consistent across salt levels indicating cultivar differences in threshold levels of salt tolerance. All plant parameters decreased significantly in all cultivars with increasing salinity. However, leaf area, shoot and root fresh weight were relatively more affected and the magnitude of reduction varied between cultivars. Limited differences between cultivars for salt tolerance were seen during vegetative growth. An index combining all plant parameters measured, suggested that V₂, V₃, V₅ and BR23 were relatively tolerant of salinity than others. Neither reduced photosynthetic capacity nor reduced turgor appeared to be the major reason for the reduced growth. Rather, reduced growth may be the result of disturbed mineral nutrition. There was no correlation between sensitivity at germination and later growth stages. The results suggested that screening of rice cultivars for salt tolerance should be at salt sensitive stages.

Keywords: Salinity, Growth, Rice

Location: Ben Reid Garden Centre, Aberdeen, UK

Start Date:

End Date:

Program Area: Risk Management in Agriculture

Commodity: Rice

Objectives:

To evaluate the salt tolerance at vegetative growth stages of some proposed salt tolerant rice cultivars and identification of salt tolerant ones.

Methodology:

Ten rice cultivars (Oryza sativa L.) were assessed in this experiment at four levels of salinity (0, 4.5, 8.5 or 12.5 dS m^-1). All but one (IR8) was developed by BRRI. Six have been advanced salt tolerant breeding lines (V₁-V₆). Two are popular MVs (BR29 and BR31) but their reaction to salt is not known. BR23 was included as a salt tolerant check as it is popularly being grown in salt prone areas of Bangladesh and IR8 is a known salt sensitive IRRI variety. A 4x10 factorial experiment in split plot design was used with three replications. Raising of seedlings: Sterilised seeds were imbibed in distilled water for 36 h. Then they were placed singly in module trays (65x27x5 cm, 210 modules) containing Q4 multipurpose compost (Ben Reid Garden Centre, Aberdeen, UK), seeds were covered by compost and well moistened. The module trays containing the seeds were maintained in a growth chamber at 26°C and were irrigated at regular intervals. After 3 days the young seedlings were transferred to the glass house where the temperature varied between 36 and 17°C. Soil collection and preparation: Soil was collected from Craibstone Estate, Aberdeen (Scottish Agricultural College). The texture of the soil was sandy loam. The soil was air dried for 10 days and then sieved through a 2 mm sieve. Growing of plants/salt application/sample collection: Nine 3 week-old seedlings (4th leaf unfolded) were transplanted in 12.5x12.5x11 cm deep pots containing 1.5 kg of sieved soil pre-moistened with 500 ml of half strength Hoagland solution. Ten pots were placed in 65x27x10 cm trays. Each tray was considered as a main plot and each pot as a sub-plot. Two weeks after transplanting (when plants had recovered from any transplanting shock) salt solutions were applied in each tray according to the treatments. To avoid osmotic shock salt solutions were added in three equal increments over a 6 day period until the expected conductivity (4.5, 8.5 and 12.5 dS m^-1) was reached. Each tray contained about 8 liters of either salt solution or tap water. Management and sampling dates were recorded. After completion of second sampling (63 d) about 250 ml of half strength Hoagland solution were added to each pot to ensure a sufficient supply of essential nutrients for the plants. Salt solutions were collected every 24 h from each tray and electric conductivity (EC) values were measured with a conductivity meter (Jenway 4010, UK) and necessary adjustments were made. Plant samples were harvested first 14 days after salt initiation (i.e. 49 days from seeding) and then three further times each at 14 d interval. Leaf area, shoot height, tillers per plant, root length and fresh and dry weights of shoot and roots were measured. Measurement of different growth parameters: Shoot height was measured from the root base to the tip of the longest leaf, excluding any dead portion. Root lengths were measured from the root-shoot junction to the tip of the longest root. Leaf area (green portion only) was measured by a leaf area meter (model MK2, DELTA-T DEVICES, Burwell, England). Plant samples were dried at 70°C for 72 h for dry weight measurements. The data were analysed using analysis of variance in GENSTAT. The statistical significance of differences between pairs of treatments was determined by Student’s t-test.

Source of Information: Journal of Agronomy, 3: 1-10, 2004; ISSN 1680-8207

Article Link (Online Journal): DOI: 10.3923/ja.2004.1.10; URL: http://scialert.net/abstract/?doi=ja.2004.1.10

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The result of the present study demonstrated that rice, in common with certain other cereals (e.g. wheat, corn), is highly sensitive to salt with severe effects even at 4.5 dS/m. The relative salt sensitivity of cultivars was not consistent across salt levels. At higher salt levels cultivar differences were not pronounced. Nevertheless, V₂, V₃, V₅ and BR23 were observed to have relatively higher tolerance than others.

Knowledge Management: Journal