Genome-wide association study identifies five new cadmium uptake loci in wheat.

Cadmium (Cd) toxicity is a serious threat to future food security and health safety. To identify genetic factors contributing to Cd uptake in wheat, we conducted a genome-wide association study with genotyping from 90K SNP array. A spring wheat diversity panel was planted under normal conditions and Cd stress (50 mg Cd/kg soil). The impact of Cd stress on agronomic traits ranged from a reduction of 16% in plant height to 93% in grain iron content. Individual genotypes showed a considerable variation for Cd uptake and translocation subdividing the panel into three groups: (1) hyper-accumulators (i.e. high Leaf_Cd and low Seed_Cd ), (2) hyper-translocators (i.e. low Leaf_Cd and high Seed_Cd ), and (3) moderate lines (i.e. low Leaf_Cd and low Seed_Cd ). Two lines (SKD-1 and TD-1) maintained an optimum grain yield under Cd stress and were therefore considered as Cd resistant lines. Genome-wide association identified 179 SNP-trait associations for various traits including 16 for Cd uptake at a significance level of P < .001. However, only five SNPs were significant after applying multiple testing correction. These loci were associated with seed-cadmium, grain-iron, and grain-zinc: qSCd-1A, qSCd-1D, qZn-2B1, qZn-2B2, and qFe-6D. These five loci had not been identified in the previously reported studies for Cd uptake in wheat. These loci and the underlying genes should be further investigated using molecular biology techniques to identify Cd resistant genes in wheat.

Mechanistic elucidation of germination potential and growth of wheat inoculated with exopolysaccharide and ACC- deaminase producing Bacillus strains under induced salinity stress.

The potential of plant growth regulating microorganisms present in the soil can be explored towards the purpose of identifying salt tolerant strategies and crop cultivars. Current study was designed to elucidate the capabilities of salt stress tolerant plant growth promoting rhizobacteria (PGPR) Bacillus siamensis (PM13), Bacillus sp. (PM15) and Bacillus methylotrophicus (PM19) in undermining the effects of salt stress on wheat seedling. Strains were characterized for their IAA (81-113 µM/ml), ACC-deaminase (0.68-0.95 µM/mg protein/h) and exopolysaccharide (EPS) (0.62-0.97 mg/ml) producing activity both under normal and NaCl stressed conditions. Effects of bacterial inoculation on germination and seedling growth of wheat variety Pakistan-13 was observed under induced salinity stress levels (0, 4, 8, 16 dS/m). All the morpho-physiological characteristics of wheat seedlings were affected drastically by the NaCl stress and the growth parameters expressed a negative relationship with increased NaCl levels. PGPR application had a very positive influence on germination rate of wheat seedlings, root and shoot length, photosynthetic pigments etc. Elongated roots and enhanced vegetative shoot growth as well as seedling's fresh and dry weights were highest in plants treated with B. methylotrophicus PM19. Sequestration of Na+ ion by EPS production and degradation of exuded ACC into a-ketobutyrate and ammonia by ACCD bacteria efficiently reduced the impact of salinity stress on wheat growth. Current findings suggested that the used PGPR strains are potential candidates for improving crop growth in salt stressed agricultural systems. However further research validation would be necessary before large scale/field application.