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An aerobic 15N microcosmic experiment was conducted to compare the inhibitory effects of the biological nitrification inhibitor (BNI), methyl 3-(4-hydroxyphenyl) propionate (MHPP) at rates of 500 and 1000 mg kg−1 with the synthetic nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) at 1% of applied NH4+, on the gross nitrification rate (n_gross) and on the abundance and community composition of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) of two contrasting soils (pH: 5.10 vs. 8.15, clay content 17.8 vs. 30.8). DMPP inhibited 56.6% of n_gross in the acidic soil and 50.3% in the calcareous soil, whereas MHPP inhibited 18.3–55.5% of n_gross in the acidic soil and 14.1–20.2% in the calcareous soil. MHPP used at the high rate showed the same inhibition on n_gross as DMPP in the acidic soil but not in the calcareous soil. DMPP and MHPP likely regulated n_gross by causing niche differentiation between AOA and AOB. Moreover, the community composition of AOB was more sensitive to nitrification inhibitor application than that of AOA, particularly in the acidic soil. However, the response of AOB community composition was less sensitive to the application of MHPP than to that of DMPP. MHPP mainly targeted Nitrosospira clusters 3a.2, 3b.2, and 9 of the AOB in the acidic soil.

Key messageMajor and environmentally stable QTL for flag leaf-related traits in wheat were identified and validated across ten environments using six populations with different genetic backgrounds.Flag leaf size and posture are two important factors of “ideotype” in wheat. Despite numerous studies on genetic analysis of flag leaf size including flag leaf length (FLL), width (FLW), area (FLA) and the ratio of length/width (FLR), few have focused on flag leaf posture including flag leaf angle (FLANG), opening angle (FLOA) and bend angle (FLBA). Further, the numbers of major, environmentally stable and verified genetic loci for flag leaf-related traits are limited. In this study, QTL for FLL, FLW, FLA, FLR, FLANG, FLOA and FLBA were identified based on a recombinant inbred line population together with values from up to ten different environments. Totally, eight major and stably expressed QTL were identified. Three co-located chromosomal intervals for seven major QTL were identified. The five major QTL QFll.sicau-5B.3 and QFll.sicau-2D.3 for FLL, QFlr.sicau-5B for FLR, QFlw.sicau-2D for FLW and QFla.sicau-2D for FLA were successfully validated by the tightly linked Kompetitive Allele Specific PCR (KASP) markers in the other five populations with different genetic backgrounds. A few genes related to leaf growth and development in intervals for these major QTL were predicated. Significant relationships between flag leaf- and yield-related traits were evidenced by analyses of Pearson correlations, conditional QTL and genetic mapping. Taken together, these results provide valuable information for understanding flag leaf size and posture of “ideotype” as well as fine mapping and breeding utilization of promising loci in bread wheat.

Aims Nitrogen (N) application is often known to influence various properties in Chinese fir growth, but the regeneration failure and productivity decline in Chinese fir plantations are often affected by allelochemical compounds. Little is known about the interactive effect of allelochemicals and N sources on the plant growth in Chinese fir seedlings. Methods Chinese fir seedlings were respectively subjected to the addition of ammonium (NH 4 + ), nitrate (NO 3 − ), p -hydroxybenzoic acid ( p HBA) and their combined additions. Results The p HBA addition alone promoted Chinese fir seedlings growth, but this effect was differentially affected by the interaction with NH 4 + or NO 3 − . Both NH 4 + and NO 3 − application improved plant growth, but the stimulatory effect of NO 3 − was weakened with addition of p HBA. Although NO 3 − addition combined with p HBA increased N accumulation in roots, the enzymes activities related to N assimilation were significantly decreased. These negative influences were also manifested through the decreased photosynthetic capacity, the reduction in photosynthates production and accumulation, and the destruction of chloroplast structural integrity. Moreover, the C/N ratio in root was obviously decreased and N assimilation was inhibited under the combined treatment of p HBA and NO 3 − , thereby aggravating C − N imbalance. Conclusions The Chinese fir seedlings shifted their N uptake preference from NO 3 − to NH 4 + when p HBA were added in soil. The dominant N source and allelochemicals interaction should be considered for Chinese fir growth.

Key messageEight major and stably expressed QTL for flag leaf morphology across eleven environments were identified and validated using newly developed KASP markers in seven biparental populations with different genetic backgrounds.Flag leaf morphology is a determinant trait influencing plant architecture and yield potential in wheat (Triticum aestivum L.). A recombinant inbred line (RIL) population with a 55 K SNP-based constructed genetic map was used to map quantitative trait loci (QTL) for flag leaf length (FLL), width (FLW), area (FLA), angle (FLANG), opening angle (FLOA), and bend angle (FLBA) in eleven environments. Eight major QTL were detected in 11 environments with 5.73–54.38% of explained phenotypic variation. These QTL were successfully verified using the newly developed Kompetitive Allele Specific PCR (KASP) markers in six biparental populations with different genetic backgrounds. Among these 8 major QTL, two co-located intervals were identified. Significant interactions for both FLL- and FLW-related QTL were detected. Comparison analysis showed that QFll.sau-SY-2B and QFla.sau-SY-2B are likely new loci. Significant relationships between flag leaf- and yield-related traits were observed and discussed. Several genes associated with leaf development including the ortholog of maize ZmRAVL1, a B3-domain transcription factor involved in regulation of leaf angle, were predicted in physical intervals harboring these major QTL on reference genomes of bread wheat ‘Chinese spring’, T. turgidum, and Aegilops tauschii. Taken together, these results broaden our understanding on genetic basis of flag leaf morphology and provide clues for fine mapping and marker-assisted breeding wheat with optimized plant architecture for promising loci.

Key MessageA novel and major QTL for the effective tiller number was identified on chromosomal arm 1BL and validated in two genetic backgroundsThe effective tiller number (ETN) substantially influences plant architecture and the wheat yield improvement. In this study, we constructed a genetic map of the 2SY (20828/SY95-71) recombinant inbred line population based on the Wheat 55K array as well as the simple sequence repeat (SSR) and Kompetitive Allele Specific PCR (KASP) markers. A comparison between the genetic and physical maps indicated the marker positions were consistent in the two maps. Additionally, we identified seven tillering-related quantitative trait locus (QTLs), including Qetn-sau-1B.1, which is a major QTL localized to a 6.17-cM interval flanked by markers AX-89635557 and AX-111544678 on chromosome 1BL. The Qetn-sau-1B.1 QTL was detected in eight environments and explained 12.12–55.71% of the phenotypic variance. Three genes associated with the ETN were detected in the physical interval of Qetn-sau-1B.1. We used a tightly linked KASP marker, KASP-AX-110129912, to further validate this QTL in two other populations with different genetic backgrounds. The results indicated that Qetn-sau-1B.1 significantly increased the ETN by up to 23.5%. The results of this study will be useful for the precise mapping and cloning of Qetn-sau-1B.1.

Strategies to reduce cadmium (Cd) in rice grain, below concentrations that represent serious human health concerns, require that the mechanisms of Cd distribution and accumulation within rice plants be established. Here, a comprehensive hydroponic experiment was performed to investigate the differences in the Cd uptake, chelation and compartmentalization between high (D83B) and low (D62B) Cd-accumulation cultivars contrasting in Cd accumulation in order to establish the roles of these processes in limiting Cd translocation from root to shoot. D83B showed 3-fold higher Cd accumulation in the shoots than the cultivar D62B. However, a short-term Cd uptake experiment showed more Cd uptake by D62B than by D83B. The distribution of Cd in roots and shoots differed significantly. D83B translocated 38% of total Cd taken up to the shoots, whereas D62B retained most of the Cd in the roots. D62B had higher amounts of non-protein thiols (NPTs) and glutathione (GSH) than D83B. The NPT and Cd distribution ratio (CDR) in the anionic form in the roots of D62B increased gradually as Cd concentration increased. In D83B, in contrast, levels of CDR in the cationic form increased significantly from 22.10 to 43.37%, while NPT only increased slightly. Furthermore, the percentage of Cd ions retained in thiol-rich peptides, especially in the HMW complexes, was significantly higher in D62B compared with D83B. However, D83B possessed a greater proportion of potentially mobile (cationic) Cd in the roots and showed superior Cd translocation from root to shoot. Taken as a whole, the results presented in this study revealed that Cd chelation, compartmentalization and adsorption contribute to the Cd retention in roots.

Background Phosphorus deficiency is a major limiting factors for affecting crop production globally. To understand the genetic variation of phosphorus-deficiency-tolerance, a total of 15 seedling traits were evaluated among 707 Chinese wheat landraces under application of phosphorus (AP) and non-application of phosphorus (NP). A total of 18,594 single-nucleotide polymorphisms and 38,678 diversity arrays technology sequencing markers were used to detect marker-trait associations under AP and NP. Results Top ten genotypes with extremely tolerance and bottommost ten genotypes with extremely sensitivity were selected from 707 Chinese wheat landraces for future breeding and genetic analysis. A total of 55 significant markers (81 marker-trait associations) for 13 traits by both CMLM and SUPER method. These were distributed on chromosomes 1A, 1B, 2A, 2B, 2D, 3A, 4B, 5A, 5B, 6A, 6B, 6D, 7A and 7B. Considering the linkage disequilibrium decay distance, 25 and 12 quantitative trait loci (QTL) were detected under AP and NP, respectively (9 QTL were specific to NP). Conclusions The extremely tolerant landraces could be used for breeding phosphorus-deficiency-tolerant cultivars. The QTL could be useful in wheat breeding through marker-assisted selection. Our findings provide new insight into the genetic analysis of P-deficiency-tolerance, and will be helpful for breeding P-deficiency-tolerant cultivars.

Controlled release fertilizer (CRF) has been shown to increase crop yield and N use efficiency (NUE) compared with traditional chemical fertilizer (TF). However, few studies examined the effects of CRF on CH 4 , N 2 O, and NO emissions simultaneously in alkaline paddy fields under rice–wheat rotation. In the present study, we conducted a 2-year field experiment to compare the effects of different CRF application strategies on these gas emissions with those of TF and explored the effects of CRF on global warming potential (GWP), crop yields, and greenhouse gas emission intensity (GHGI). Results showed that CRF can reduce 0.98–14.3%, 13.3–21.1%, and 8.22–16.3% of CH 4 , N 2 O, and NO emissions, respectively, in the studied alkaline paddy field. CRF reduce CH 4 emission probably by regulating soil NH 4 + concentration. CRF reduce N 2 O and NO emissions probably by regulating inorganic N content in the studied alkaline paddy soil. CRF had the same effect on annual crop yield as TF, especially when CRF was applied twice in each season and had the same N application rate as TF. Annual crop yields and the agronomic efficiency of N (AE N ) increased by 8.24% and 21.6%, respectively. On the average of the two rice–wheat rotation cycles, GHGI significantly decreased by up to 14.1% after the application of CRF as relative to that after the application of TF ( P  < 0.05). These results suggest that CRF is an environment-friendly N fertilization strategy for mitigating GWP and ensuring high crop yield in an alkaline paddy field under rice–wheat rotation.

Key messageWe identified and validated two stable grain filling rate (GFR) quantitative trait loci (QTL) in wheat that positively influenced several yield-related traits. Among them, QGfr.sicau-7D.1 was a novel GFR QTL.The grain filling rate (GFR) plays a crucial role in determining grain yield. To advance the current understanding of the genetic characteristics underlying the GFR in common wheat, three recombinant inbred line populations were used to map and validate GFR quantitative trait loci (QTL). Using a high-density genetic linkage map, 10 GFR QTL were detected. They were located on chromosomes 2D, 4A, 4B, 5B, 6D, 7A and 7D, explained 4.99–12.62% of the phenotypic variation. Two of them, QGfr.sicau-6D and QGfr.sicau-7D.1, were detected in all four environments tested and their genetic effect was validated by closely linked kompetitive allele specific PCR (KASP) markers in different genetic backgrounds. The effects of these two GFR QTL on other yield-related traits were also estimated. QGfr.sicau-6D had a significant positive influence (p < 0.01) on thousand kernel weight, kernel width, kernel volume, and kernel surface area. QGfr.sicau-7D.1 had a significant positive influence (p < 0.01) on thousand kernel weight and kernel length. Furthermore, QGfr.sicau-7D.1 was a completely novel QTL for GFR; several genes associated with grain growth and development were predicted in its physical interval. These results will facilitate molecular marker-assisted selection of wheat with high-confidence QTL for GFR and fine mapping of genes associated with GFR, thereby contributing to yield improvement.

The barley chromosome 3H accommodates many semi-dwarfing genes. To characterize these genes, the two-rowed semi-dwarf Chinese barley landrace 'TX9425' was crossed with the Australian barley variety 'Franklin' to generate a doubled haploid (DH) population, and major QTLs controlling plant height have been identified in our previous study. The major QTL derived from 'TX9425' was targeted to investigate the allelism of the semi-dwarf gene uzu in barley. Twelve sets of near-isogenic lines and a large NILF2 fine mapping population segregating only for the dwarfing gene from 'TX9425' were developed. The semi-dwarfing gene in 'TX9425' was located within a 2.8 cM region close to the centromere on chromosome 3H by fine mapping. Molecular cloning and sequence analyses showed that the 'TX9425'-derived allele contained a single nucleotide substitution from A to G at position 2612 of the HvBRI1 gene. This was apparently the same mutation as that reported in six-rowed uzu barley. Markers co-segregating with the QTL were developed from the sequence of the HvBRI1 gene and were validated in the 'TX9425'/'Franklin' DH population. The other major dwarfing QTL derived from the Franklin variety was distally located on chromosome 3HL and co-segregated with the sdw1 diagnostic marker hv20ox2. A third dwarfing gene, expressed only in winter-sown trials, was identified and located on chromosome 3HS. The effects and interactions of these dwarfing genes under different growing conditions are discussed. These results improve our understanding of the genetic mechanisms controlling semi-dwarf stature in barley and provide diagnostic markers for the selection of semi-dwarfness in barley breeding programs.