Impacts of long-term irrigation with coalmine effluent contaminated water on trace metal contamination of topsoil and potato tubers in Dinajpur area, Bangladesh.

Rapid depletion of groundwater and climate change mediated shifting precipitation pattern is forcing farmers to look for alternative irrigation options like wastewater. However, routine irrigation with trace metal contaminated wastewaters could potentially pollute soil as well as cause health risks through the consumption of food products grown in contaminated soil. Thus, the present study aimed to investigate the trace metals build-up status in topsoil and potato (Solanum tuberosum L.) tubers upon continuous irrigation with coalmine effluent contaminated wastewater compared to irrigation with groundwater and surface water over three consecutive years. Soil pollution status and human health risk associated with consumption of potato tubers grown on wastewater-irrigated soil was also assessed in this study. Three separate experimental sites differing in irrigation source (groundwater, surface water, and coalmine wastewater) were selected near Barapukuria Coal Mining Company Limited located at Parbatipur upazilla of Dinajpur district, Bangladesh. Nine trace metals namely arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) were estimated. Results showed significantly higher trace metal content in both soil and potato tubers due to wastewater irrigation. Wastewater suitability for irrigation regarding Cd, Cr, Cu, Fe, Ni and Pb were off the permissible level although the soil contamination with trace metals and their levels in potato tubers remained within the safety limit. Health risk assessment revealed that, consumption of potato tubers grown in wastewater-irrigated soil remained safe although health risk associated with Cr was almost at the border. The study exclusively highlighted the core massage that, trace metal contamination of both soil and potatoes cultivated in them was increasing alarmingly due to three years of wastewater-irrigation. Although the extent of contamination was below critical limit, it can potentially become hazardous in years to come unless wastewater-irrigation is checked. This study was successful to provide valuable insights regarding the potential environmental and human health threats that might arise due to unmindful irrigation of contaminated coalmine wastewater. Besides, this study should prove useful in strategizing safety measures for cropping under trace metal contaminated soils and for planning industrial effluent disposal to avoid agricultural soil contamination.

Assessment of genetic variation among wheat genotypes for drought tolerance utilizing microsatellite markers and morpho-physiological characteristics.

Drought is a major abiotic stress that severely limits sustainable wheat (Triticum aestivum L.) productivity via morphological and physio-biochemical alterations of cellular processes. The complex nature and polygenic control of drought tolerance traits make breeding tolerant genotypes quite challenging. However, naturally occurring variabilities among wheat germplasm resources could potentially help combating drought. The present study was conducted to assess the drought tolerance of 18 Bangladeshi hexaploid wheat genotypes, focusing on the identification of potent sources of diversity by combining microsatellite markers, also known as single sequence repeat markers, and morpho-physiological characteristics that might help accelerating wheat crop improvement programs. Initially, the genotypes were evaluated using 25 microsatellite markers followed by an on-field evaluation of 7 morphological traits (plant height, spike number, spike length, grains per spike, 1000-grain weight, grain yield, biological yield) and 6 physiological traits (SPAD value, membrane stability index, leaf relative water content, proline content, canopy temperature depression, and leaf K+ ion content). The field-trial was conducted in a factorial fashion of 18 wheat genotypes and two water regimes (control and drought) following a split-plot randomized complete block design. Regardless of genotype, drought was significantly damaging for all the tested traits; however, substantial variability in drought stress tolerance was evident among the genotypes. Spike length, 1000-grain weight, SPAD value, leaf relative water content, canopy temperature depression, proline content, and potassium (K+) ion content were the most representative of drought-induced growth and yield impairments and also correlated well with the contrasting ability of genotypic tolerance. Microsatellite markers amplified 244 alleles exhibiting 79% genetic diversity. Out of 25 markers, 23 was highly polymorphic showing 77% average polymorphism. Morpho-physiological trait-based hierarchical clustering and microsatellite marker-based neighbor-jointing clustering both revealed three genotypic clusters with 71% co-linearity between them. In both cases, the genotypes Kanchan, BAW-1147, BINA Gom 1, BARI Gom 22, BARI Gom 26, and BARI Gom 33 were found to be comparatively more tolerant than the other tested genotypes, showing potential for cultivation in water-deficit environments. The findings of this study would contribute to the present understanding of drought tolerance in wheat and would provide a basis for future genotype selection for drought-tolerant wheat breeding programs.

Sett priming with salicylic acid improves salinity tolerance of sugarcane (Saccharum officinarum L.) during early stages of crop development.

Sugarcane (Saccharum officinarum L.), a globally cultivated carbohydrate producing crop of industrial importance is being challenged by soil salinity due to its glycophytic nature. Water stress coupled with cellular and metabolic alterations resulting from excess sodium (Na+) ion accumulation is irreversibly damaging during early crop developmental stages that often results in complete crop failure. This study therefore aimed to explore the potential of salicylic acid as a sett priming material to mitigate the negative effects of salt stress on sugarcane during germination and early growth stages. Five doses of salicylic acid (0 [hydropriming] [control], 0.5 mM, 1 mM, 1.5 mM and 2 mM) were tested against three levels of salinity (0.5 dS m-1 [control], 4 dS m-1, and 8 dS m-1) within a polyhouse environment. Results revealed 11.2%, 18.5%, 25.4%, and 38.6%, average increase in final germination, germination energy, seedling length and seedling vigor index respectively with a subsequent reduction of 21% mean germination time. Investigations during early seedling growth revealed 21.6%, 17.5%, 27.0%, 39.9%, 10.7%, 11.5%, 17.5%, 47.9%, 35.3% and 20.5% overall increase in plant height, total leaf area, shoot dry matter, root dry matter, leaf greenness, relative water content, membrane stability index, proline content, total antioxidant activity and potassium (K+) ion accumulation respectively with a subsequent reduction of 24.9% Na+ ion accumulation and 35.8% Na+/K+ ratio due to salicylic acid priming. Germination, seedling growth and recovery of physiochemical traits were highly satisfactory in primed setts than non-primed ones even under 8 dS m-1 salinity level. This study should provide useful information for strategizing salinity management approaches for better productivity of sugarcane.