Biotechnological Advances to Improve Abiotic Stress Tolerance in Crops.

The major challenges that agriculture is facing in the twenty-first century are increasing droughts, water scarcity, flooding, poorer soils, and extreme temperatures due to climate change. However, most crops are not tolerant to extreme climatic environments. The aim in the near future, in a world with hunger and an increasing population, is to breed and/or engineer crops to tolerate abiotic stress with a higher yield. Some crop varieties display a certain degree of tolerance, which has been exploited by plant breeders to develop varieties that thrive under stress conditions. Moreover, a long list of genes involved in abiotic stress tolerance have been identified and characterized by molecular techniques and overexpressed individually in plant transformation experiments. Nevertheless, stress tolerance phenotypes are polygenetic traits, which current genomic tools are dissecting to exploit their use by accelerating genetic introgression using molecular markers or site-directed mutagenesis such as CRISPR-Cas9. In this review, we describe plant mechanisms to sense and tolerate adverse climate conditions and examine and discuss classic and new molecular tools to select and improve abiotic stress tolerance in major crops.

Responses of Labile Organic Carbon and Extractable Cadmium Fractions in an Agricultural Soil Following Long-Term Repeated Application of Pig Manure and Effective Microbes.

Long-term pig manure addition has been widely applied in red soil to improve soil fertility. However, the influence of combined utilization of pig manure and effective microbes (EM) on soil organic carbon (SOC) and Cd are not well understood. This study conducted a 23-year (1996-2019) long-term fertilization field trial to investigate the changes of different fractions of SOC and Cd under chemical fertilization (CF), pig manure (PM), and pig manure with effective microbes (PM + EM) treatments in an agricultural soil of Jiangxi Province, South China. The results showed that the pig manure addition significantly enhanced the contents of SOC and Cd in the soils compared with the CF treatments. Furthermore, with the increment of SOC, the PM + EM treatment significantly increased the contents of soil microbial biomass carbon, dissolved organic carbon and easily oxidizable carbon compared with the pig manure application alone. Meanwhile, compared with the CF treatments, the EM addition significantly enhanced the exchangeable and oxidizable fractions of Cd, thus the potential Cd environment risk due to pig manure application should be carefully assessed.

Phytostabilization of acidic mine tailings with biochar, biosolids, lime, and locally-effective microbes: Do amendment mixtures influence plant growth, tailing chemistry, and microbial composition?

Abandoned mine lands present persistent environmental challenges to ecosystems and economies; reclamation an important step for overcoming these challenges. Phytostabilization is an elegant and cost-effective reclamation strategy, however, establishing plants on severely degraded soils is problematic, often requiring soil amendment additions. We evaluated whether amendment mixtures composed of lime, biochar, biosolids, and locally effective microbes (LEM) could alleviate the constraints that hinder phytostabilization success. We hypothesized that 1) plants grown in tailings amended with lime, biochar, and biosolids (LBB) would establish faster and grow larger than plants grown in tailings amended with lime only, and 2) the LEM source would influence microbial community function and structure in amended mine tailings. We conducted a greenhouse study that simulated in situ conditions to measure the influence of LBB-LEM amendment blends on plant growth, plant nutrients, metal concentrations, microbial function, and microbial community structure. Blue wildrye [Elymus glaucus Buckley ssp. Jepsonii (Burtt Davy) Gould] was grown in tailings collected from the Formosa mine site amended with various combinations of LBB-LEM. The above and below ground biomass of plants grown in mine tailings amended with LBB was 3 to 4 times larger than the biomass of plants grown in tailings amended only with lime. Although the LEM addition did not influence immediate plant growth, it did affect nutrient content and altered the rhizosphere community membership. As such, it is not yet clear if LEM-driven alterations in microbial membership will advance mine reclamation strategies by improving long-term growth.

Microbes as vital additives for solid waste composting.

Composting is a natural process that stems through microbial succession, marking the degradation and stabilization of organic matter present in waste. The use of microbial additives during composting is considered highly efficient, likely to enhance the production of different enzymes resulting in better rate of waste degradation. In lesser developed countries, composting has emerged as a vital technology to recycle the biodegradable waste while generating a useful product. Depending on the composition of the waste material, it can either directly undergo composting or homogenized prior to secondary waste treatment methods such as landfilling. However, a relatively expensive downstream handling all along is a main hurdle towards economics of the process. Although basic methodology and recent approaches are known in crucial aspects of the process through various reviews, exploring the behavior of effective microbial additives will be resourceful. In this review, to fill in the gap, studies related to microbial composting of municipal solid and food waste were acknowledged. Here in, factors that could slow down the composting process and affect the compost quality were addressed. Lastly, the review pictured a positive simulation and stated how excellent results, can be achieved by microbial additives during composting.