A major breeding target in Upland cotton (Gossypium hirsutum L.) is to improve the fiber quality. To address this issue, 169 diverse accessions, genotyped by 53,848 high-quality single-nucleotide polymorphisms (SNPs) and phenotyped in four environments, were used to conduct genome-wide association studies (GWASs) for fiber quality traits using three single-locus and three multi-locus models. As a result, 342 quantitative trait nucleotides (QTNs) controlling fiber quality traits were detected. Of the 342 QTNs, 84 were simultaneously detected in at least two environments or by at least two models, which include 29 for fiber length, 22 for fiber strength, 11 for fiber micronaire, 12 for fiber uniformity, and 10 for fiber elongation. Meanwhile, nine QTNs with 10% greater sizes (R2) were simultaneously detected in at least two environments and between single- and multi-locus models, which include TM80185 (D13) for fiber length, TM1386 (A1) and TM14462 (A6) for fiber strength, TM18616 (A7), TM54735 (D3), and TM79518 (D12) for fiber micronaire, TM77489 (D12) and TM81448 (D13) for fiber uniformity, and TM47772 (D1) for fiber elongation. This indicates the possibility of marker-assisted selection in future breeding programs. Among 455 genes within the linkage disequilibrium regions of the nine QTNs, 113 are potential candidate genes and four are promising candidate genes. These findings reveal the genetic control underlying fiber quality traits and provide insights into possible genetic improvements in Upland cotton fiber quality.

Plant architecture is important for cotton cultivation and breeding. In this study, two mapping generations/populations F 2 and F 2:3 in Upland cotton (Gossypium hirsutum L.), derived from 'Baimian1' and TM-1, were used to identify quantitative trait loci (QTLs) for 10 plant architecture traits. A total of 55 main-effect QTLs (M-QTLs) were detected. Four common M-QTLs, qTFB-10(F 2 /F 2:3 ) for total fruit branches, qFBL-26b(F 2 )/qFBL-26(F 2:3 ) for fruit branch length, qFBA-5(F 2 /F 2:3 ) for fruit branch angle and qFBN-26b(F 2 )/qFBN-26(F 2:3 ) for fruit branch nodes, were found. The synergistic alleles and the negative alleles can be utilized in cotton plant architecture breeding programmes according to specific breeding objectives. Altogether 54 pairs of epistatic QTLs (E-QTLs) exhibiting the interactions of additive-by-additive (AA), additive-by-dominant (AD), dominant-by-additive (DA) and dominant-by-dominant (DD) were detected. The epistasis appeared to be an important contributor to genetic variation in cotton plant architecture traits. Therefore, the identified markers associated with E-QTLs as well as M-QTLs will be of importance in future breeding programmes to develop cotton cultivars exhibiting desirable plant architecture. Key words: cottonplant architecture traitsquantitative trait locusmain-effect QTLepistatic QTL PH, two for FBL and three for ratio of PH to FBL in a recombinant inbred lines (RILs) population in Upland cotton (Gossypium hirsutum). Wang et al. (2006) identified three QTLs for FBL and one for ratio of PH to FBL in another RIL population in G. hirsutum. Song and Zhang (2009) detected 26 QTLs dispersed over 15 chromosomes in an interspecific population between G. hirsutum and Gossypium barbadense for six plant architecture traits: first fruiting branch position, stem leaf size, PH, SIL, FBA and FBIL. Li et al. (2013) identified five QTLs for PH, 10 for SNL, six for SIL, nine for TFB, three for EFB, eight for FBL, eight for FBN, eight for FBIL, 10 for TFN and six for FBA in two F 2:3 Upland cotton populations. Although there are a few reports applying molecular marker techniques to detect QTLs for cotton plant architecture traits, reliable QTLs *Cheng-Qi Li and Li Song contributed equally to this work.

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Sulfamethazine (SM2) is one of the sulfonamide antibiotics that is frequently detected in aquatic environment. Given the complex structure of SM2 and its potential threat to the environment, it is necessary to determine the degradation behavior of high-concentration SM2. The mechanisms of community structure and diversity of activated sludge were analyzed. A novel SM2-degrading strain YL1 was isolated which can degrade SM2 with high concentration of 100 mg L −1. Strain YL1 was identified as Paenarthrobacter ureafaciens and there was also a significant increase in the genus during acclimation. Additional SM2 metabolic mechanisms and genomic information of YL1 were analyzed for further research. The succession of the community structure also investigated the effect of SM2 on the activated sludge. This result not only advances the current understanding of microbial ecology in activated sludge, but also has practical implications for the design and operation of the environmental bioprocesses for treatment of antimicrobial-bearing waste streams.