Response of soil microbial community to application of biochar in cotton soils with different continuous cropping years.

The bacterial community in soils of cotton that have continuously been cropped for 2 years, 6 years, 11 years and 14 years and treated with biochar (B0, 0 t·ha-1; B1, 12.5 t·ha-1; and B2, 20 t·ha-1) was investigated using next-generation sequencing. Of the 45 bacterial genera (relative abundance ratio of genera greater than 0.3%), 21 genera were affected (p < 0.05) by the biochar treatment, whereas 20 genera were affected by the continuous cropping. Between the soils that have been continuously cropped for 2 years and 14 years, 12 different genera were significantly observed (p < 0.05), and 6 genera belonged to the phylum Acidobacteria. The relative abundance of Sphingomonas and Pseudomonas in the biochar-treated soils was significantly higher than that in the soil without biochar treatment (p < 0.05), and the relative abundance of Sphingomonas and Pseudomonas in soils that have been continuously cropped for 2 years and 6 years was significantly higher than that in the soils continuously cropped for 11 years and 14 years (p < 0.05). The results suggest that the biochar application has a significant impact on the soil bacterial community, which may improve the microbial diversity of continuous cropping systems in cotton soils.

Identification of associated SSR markers for yield component and fiber quality traits based on frame map and Upland cotton collections.

Detecting QTLs (quantitative trait loci) that enhance cotton yield and fiber quality traits and accelerate breeding has been the focus of many cotton breeders. In the present study, 359 SSR (simple sequence repeat) markers were used for the association mapping of 241 Upland cotton collections. A total of 333 markers, representing 733 polymorphic loci, were detected. The average linkage disequilibrium (LD) decay distances were 8.58 cM (r2 > 0.1) and 5.76 cM (r2 > 0.2). 241 collections were arranged into two subgroups using STRUCTURE software. Mixed linear modeling (MLM) methods (with population structure (Q) and relative kinship matrix (K)) were applied to analyze four phenotypic datasets obtained from four environments (two different locations and two years). Forty-six markers associated with the number of bolls per plant (NB), boll weight (BW), lint percentage (LP), fiber length (FL), fiber strength (FS) and fiber micornaire value (FM) were repeatedly detected in at least two environments. Of 46 associated markers, 32 were identified as new association markers, and 14 had been previously reported in the literature. Nine association markers were near QTLs (at a distance of less than 1-2 LD decay on the reference map) that had been previously described. These results provide new useful markers for marker-assisted selection in breeding programs and new insights for understanding the genetic basis of Upland cotton yields and fiber quality traits at the whole-genome level.

Quantitative phosphoproteomics analysis of nitric oxide-responsive phosphoproteins in cotton leaf.

Knowledge of phosphorylation events and their regulation is crucial to understanding the functional biology of plant proteins, but very little is currently known about nitric oxide-responsive phosphorylation in plants. Here, we report the first large-scale, quantitative phosphoproteome analysis of cotton (Gossypium hirsutum) treated with sodium nitroprusside (nitric oxide donor) by utilizing the isobaric tag for relative and absolute quantitation (iTRAQ) method. A total of 1315 unique phosphopeptides, spanning 1528 non-redundant phosphorylation sites, were detected from 1020 cotton phosphoproteins. Among them, 183 phosphopeptides corresponding to 167 phosphoproteins were found to be differentially phosphorylated in response to sodium nitroprusside. Several of the phosphorylation sites that we identified, including RQxS, DSxE, TxxxxSP and SPxT, have not, to our knowledge, been reported to be protein kinase sites in other species. The phosphoproteins identified are involved in a wide range of cellular processes, including signal transduction, RNA metabolism, intracellular transport and so on. This study reveals unique features of the cotton phosphoproteome and provides new insight into the biochemical pathways that are regulated by nitric oxide.