Differential grain quality responses of rice varieties under combined salt, cadmium and arsenic stresses

Overview

This pot study evaluated how combined abiotic stresses from salinity (150 mM NaCl), cadmium (300 µM CdCl2), and arsenic (250 µM sodium arsenite, Na AsO2) individually and in combination affect rice grain quality across four indica rice varieties from two countries (Pakistan and Sri Lanka). The study assessed milling properties, physical grain traits, cooking characteristics, and functional properties (amylose content, gel consistency, alkali spreading value, aroma) across eight treatments: control, salt (S), cadmium (CD), arsenic (AS), combined salt+arsenic (S+AS), salt+cadmium (S+CD), cadmium+arsenic (CD+AS), and all three combined (COM).

This is a stress-response pot study focused on grain quality parameters rather than grain metal concentrations. It provides context for understanding how cadmium and arsenic exposure affects rice grain quality attributes rather than reporting finished-food contamination levels.

Key numbers

All values are as reported in the paper’s own units.

Grain yield:

• Head rice yield was significantly reduced to 40 to 45% in KS and AT under combined stress (COM), compared to controls
• Degree of milling increased to 42% under COM in the AT variety (highest observed)

Milling effects:

• All stress treatments led to an increase in the degree of milling across varieties compared to controls
• Previous studies cited within the paper showed a higher degree of milling can reduce heavy metal concentrations in rice grains, with reductions in cadmium (Cd) (3%), lead (Pb) (29%), Cu (6%), and Zn (15%)

Amylose content:

• COM treatment consistently reduced amylose content to either low or intermediate levels in all varieties
• S+CD treatment notably reduced amylose in KS (p < 0.001)
• AS treatment increased amylose content in BG and AT (p < 0.01)

Gel consistency:

• BG variety shifted from soft (control) to hard under SAS, SCD, and CDAS treatments
• KS variety: gel consistency altered from soft to hard (p < 0.001)

Cooking properties:

• Volume expansion increased significantly in SB under all treatments compared to control (p < 0.0211)
• Grain curling highest under COM treatment
• Grain bursting: highest in AT under SCD treatment (p < 0.0001)

Varietal performance:

• KS (Kala Shahkaku 282) showed the highest overall adaptability across all quality domains
• SB (Super Basmati) was the most adversely affected variety
• AT received the highest rating for cooking properties

Grain arsenic concentration: Not directly measured in this study. The study applied arsenic as a stress treatment (250 µM sodium arsenite) and evaluated its effects on grain quality rather than measuring residual grain arsenic concentrations.

Grain cadmium concentration: Not directly measured in this study.

Evidence fitness

EF-3: This is a pot study that applies cadmium and arsenic as stress treatments and measures their effects on grain quality attributes (milling, physical, cooking, functional properties) rather than on grain metal concentrations. No grain-level metal concentration data are reported. The study is relevant as context for understanding how metal stress alters rice grain quality but does not contribute direct contamination data for the wiki’s contamination profile framework. Four varieties, eight treatments, three replicates per treatment, grown in pots at NARC/COMSATS facilities in Pakistan.

Methods (brief)

Four indica rice varieties: Super Basmati (SB) and Kala Shahkaku 282 (KS) from Pakistan; Ambalanthota AT 362 (AT) and Bathalagoda BG 94/1 (BG) from Sri Lanka. Seeds sown June 2024 at NARC, Islamabad, Pakistan. Pots (2 inch height, 2 inch diameter) filled with 2 kg peat moss and soil mixture (1:1 ratio). Seedlings transferred to Hoagland-based hydroponic media after 14 days, then to field pots after 6 seedlings emerged. Abiotic stress treatments imposed at approximately 50% panicle initiation. Eight treatments: control (C), salt (S; 150 mM NaCl), cadmium (CD; 300 µM CdCl2), arsenic (AS; 250 µM Na AsO2), and dual/triple combinations. One liter of each solution applied directly to designated pots. Plants grown to maturity (harvested early October 2024). Three replicates per treatment. Milling by Paddy Husker (KHL-250, Mitsubishi). Physical properties measured by Micron Epson perfection v600 scanner and digital Vernier caliper. Cooking properties (volume expansion, elongation ratio, curling, bursting, stickiness) and functional properties (amylose, gel consistency, alkali spreading, aroma) assessed by standard methods. Two-way ANOVA with repeated measures using GraphPad Prism and R.

Implications

This study is relevant as context for understanding the downstream grain quality consequences of cadmium and arsenic contamination in rice, rather than as a source of grain contamination concentration data. The finding that combined stresses (salt + cadmium + arsenic) produced worse grain quality degradation than any single stress, and that varietal responses differed substantially, has implications for rice cultivation in regions with co-occurring salinity and heavy metal contamination. The identification of KS-282 as a stress-tolerant variety maintaining grain quality under combined stresses is potentially relevant to breeding programs aimed at reducing heavy metal impact on rice quality. However, the stress concentrations used (300 µM Cd, 250 µM As) are high and not directly representative of typical field contamination levels.

Provenance notes

• Received 8 September 2025, accepted 19 November 2025, published 27 November 2025.
• Seeds from NARC (Pakistan) and Rice Research Station, Sammanthurai, Sri Lanka.
• Experiments conducted at NARC and COMSATS University Islamabad, Pakistan.
• No grain metal concentration data reported; the study measures grain quality endpoints only.

Related evidence

• Rice
• Cadmium
• Arsenic

Update history

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