Iron Fortification in Parboiled Rice—A Rapid and Effective Tool for Delivering Iron Nutrition to Rice Consumers

Parboiled rice production accounts for nearly half of the world’s rice production. Its markets and consumer base are firmly established in South Asia and Africa where Fe-deficient populations are mostly concentrated. Our research group has pioneered the technology of Fe-fortification in parboiled rice and demonstrated its feasibility in significantly increasing Fe concentration in the endosperm (white rice) and its bioavailability in rice based diet. Fortification with Fe-EDTA during parboiling resulted in 10 to 50 folds increase in grain Fe concentration, depending on the grain properties among different rice varieties. However, the broken rice of Fe-fortified parboiled rice contained 5 times the Fe concentration of the full grain, which is often bought and consumed by people in low income category. The bioavailability of the fortified Fe is closely correlated with increasing Fe concentration in white rice (r = 0.90, p 50% to almost 100%, despite repeated rinsing before cooking depending on rice varieties. Perls’ Prussian blue staining and prolonged polishing showed that the in vitro Fe penetrated into the interior of the endosperm. Fortification at the rate up to 250 mg Fe kg–1 paddy rice has no deleterious effects on appearance, color and sensory quality and overall acceptance by parboiled rice consumers. It increased Fe concentration up to 27 mg Fe kg–1 of in white rice, compared with 5 mg Fe kg–1 in unfortified parboiled and raw white rice. As a result, we can conclude that parboiled rice is a ready and effective tool for improving Fe nutrition of rice consumers in these regions.

Arbuscular mycorrhizal fungi regulate plant mineral nutrient uptake and partitioning in iron ore tailings undergoing eco-engineered pedogenesis

Excess available K and Fe in Fe ore tailings with organic matter amendment and water-deficiencies may restrain plant colonization and growth,which hinders the formation of eco-engineered soil from these tailings for sustainable and cost-effective mine site rehabilitation.Arbuscular mycorrhizal(AM)fungi are widely demonstrated to assist plant growth under various unfavorable environments.However,it is still unclear whether AM symbiosis in tailings amended with different types of plant biomass and under different water conditions could overcome the surplus K and Fe stress for plants in Fe ore tailings,and if so,by what mechanisms.Here,host plants(Sorghum sp.Hybrid cv.Silk),either colonized or noncolonized by the AM fungi(Glomus spp.),were cultivated in lucerne hay(LH,C:N ratio of 18)-or sugarcane mulch(SM,C:N ratio of 78)-amended Fe ore tailings under well-watered(55%water-holding capacity(WHC)of tailings)or water-deficient(30%WHC of tailings)conditions.Root mycorrhizal colonization,plant growth,and mineral elemental uptake and partitioning were examined.Results indicated that AM fungal colonization improved plant growth in tailings amended with plant biomass under water-deficient conditions.Arbuscular mycorrhizal fungal colonization enhanced plant mineral element uptake,especially P,both in the LH-and SM-amended tailings regardless of water condition.Additionally,AM symbiosis development restrained the translocation of excess elements(i.e.,K and Fe)from plant roots to shoots,thereby relieving their phytotoxicity.The AM fungal roles in P uptake and excess elemental partitioning were greater in LH-amended tailings than in SM-amended tailings.Water deficiency weakened AM fungal colonization and functions in terms of mineral element uptake and partitioning.These findings highlighted the vital role AM fungi played in regulating plant growth and nutrition status in Fe ore tailings technosol,providing an important basis for involvement of AM fungi in the eco-engineered pedogenesis of Fe ore tailings.

Response of microbial communities to biochar-amended soils:a critical review

Application of biochar to soils changes soil physicochemical properties and stimulates the activities of soil microorganisms that influence soil quality and plant performance.Studying the response of soil microbial communities to biochar amendments is important for better understanding interactions of biochar with soil,as well as plants.However,the effect of biochar on soil microorganisms has received less attention than its influences on soil physicochemical properties.In this review,the following key questions are discussed:(i)how does biochar affect soil microbial activities,in particular soil carbon(C)mineralization,nutrient cycling,and enzyme activities?(ii)how do microorganisms respond to biochar amendment in contaminated soils?and(iii)what is the role of biochar as a growth promoter for soil microorganisms?Many studies have demonstrated that biochar-soil application enhances the soil microbial biomass with substantial changes in microbial community composition.Biochar amendment changes microbial habitats,directly or indirectly affects microbial metabolic activities,and modifies the soil microbial community in terms of their diversity and abundance.However,chemical properties of biochar,(especially pH and nutrient content),and physical properties such as pore size,pore volume,and specific surface area play significant roles in determining the efficacy of biochar on microbial performance as biochar provides suitable habitats for microorgan-isms.The mode of action of biochar leading to stimulation of microbial activities is complex and is influenced by the nature of biochar as well as soil conditions.

Diversity of As Metabolism Functional Genes in Pb-Zn Mine Tailings

Microbial activities impact arsenic(As) transformation in mine tailings substantially, yet little is understood on the functional diversity of As metabolism genes. This study explored this issue using a metagenomic approach coupled by a local BLASTN procedure established in our recent studies. An assembled metagenome, recovered from hypersaline and sulfidic mine tailings, was screened for As metabolism genes aio A, arr A, ars C and ars M. This was done using a local BLASTN procedure against databases of the As metabolism genes built in this study. Putative As metabolism genes detected in the assembled metagenome included 11 ars M, 20 ars C and 1 arr A full-length sequences. Together with the rRNA-based phylogenetic profiling results, a picture depicting microbial As cycling in the tailings to the genus level was obtained. It was found that most of the dominant genera in the tailings potentially harboured the genes for As reduction and/or methylation. In particular, a typical pyrite-eater present in the tailings, Thioalkalivibrio sp., was found to harbour not only ars C and ars M, but also arr A. These results highlight the unexpected diversity of As metabolism genes in the tailings, especially considering the extremely low species diversity therein. The microbial As cycling picture established here has potential use for guiding the purposeful manipulation of As biogeochemistry in the tailings.

Arbuscular mycorrhiza and plant chromium tolerance

Arbuscular mycorrhizal(AM)fungi are ubiquitous soil fungi that form symbiotic associations with most terrestrial plants.The growth and functions of AM fungi depend on carbohydrates supplied by the plants,in return,the fungi assist the plants to acquire mineral nutrients(e.g.,phosphorus)from soil.The AM symbiosis also improves plant survival in various unfavorable environments,such as metal(loid)contaminated soil.It has been well demonstrated that AM symbiosis improved plant adaptation to Cr contamination,which would have a great potential in phytoremediation and ecological restoration of Cr contaminated soils.In this paper,we have reviewed the role of AM fungi in alleviation of Cr phytotoxicity and associated factors influencing plant Cr tolerance.AM symbiosis improves plant Cr tolerance through its direct roles in Cr stabilization and transformation and indirect roles via AM symbiosis mediated nutrient acquisition and physiological regulation.Future research on physiological and molecular mechanisms underlying Cr behavior and detoxification in AM symbiosis,as well as potential use of AM fungi in ecological restoration and agriculture production in Cr contaminated soils were also proposed.