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The timing of bud flush (TBF) in the spring is one of the most important agronomic traits of tea plants (Camellia sinensis). In this study, we designed an open-pollination breeding program using ‘Emei Wenchun’ (EW, a clonal tea cultivar with extra early TBF) as a female parent. A half-sib population (n=388) was selected for genotyping using specific-locus amplified fragment sequencing. The results enabled the identification of paternity for 294 (75.8%) of the offspring, including 11 (2.8%) from EW selfing and 217 (55.9%) assigned to a common father ‘Chuanmu 217’ (CM). The putative EW×CM full-sib population was used to construct a linkage map. The map has 4,244 markers distributed in 15 linkage groups, with an average marker distance of 0.34 cM. A high degree of collinearity between the linkage map and physical map was observed. Sprouting index (SPI), a trait closely related to TBF, was recorded for the offspring population in 2020 and 2021. The trait had moderate variation with coefficients of variation of 18.5% and 17.6%. Quantitative trait locus (QTL) mapping that was performed using the linkage map identified two major QTLs and three minor QTLs related to SPI. These QTLs are distributed on Chr3, Chr4, Chr5, Chr9 and Chr14 of the reference genome. A total of 1,960 predicted genes were found within the confidence intervals of QTLs, and 22 key candidate genes that underlie these QTLs were preliminarily screened. These results are important for breeding and understanding the genetic base of TBF trait of tea plants.

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A significant but challenging task is the development of a rechargeable Zn–air battery bifunctional catalyst. Here, a supramolecular self-assembly of poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123) was designed to construct Co2P nanoparticles encapsulated in N-doped carbon nanotubes (Co2P@NCNT-x). The results show that P123 is an important factor in the formation of N-doped carbon nanotubes coated with Co2P nanoparticles. The Co2P@NCNT-4 catalyst exhibits the maximum limiting diffusion current density (5.2 mA·cm–2 under 808.9 hPa) and a more positive onset potential (0.90 V vs RHE) and half-wave potential (0.84 V vs RHE) due to the greater specific surface area and higher graphitization degree. Its potential gap is only 0.87 V versus RHE which is between the half-wave potential of the oxygen reduction reaction and the E j = 10 of the oxygen evolution reaction. The Co2P@NCNT-4-based rechargeable Zn–air battery shows the highest peak power density (217 mW·cm–2), the highest specific capacity (831.25 mA h·gZn –1 at 10 mA·cm–2), and remarkable cycle stability. This preparation method can provide ideas for designing other transition metal phosphide catalysts in the future.

It is desirable to prepare low-cost non-noble metal catalysts using a simple and efficient method. Herein, we display for the first time that nitrogen-doped hierarchical porous carbon-supported vanadium nitride (VN/NC/C-x) catalysts can be regulated by dicyandiamide (DCDA). The introduction of DCDA not only effectively controls the pore structure, but also plays an important role in adjusting oxygen vacancies and d-electrons. In addition, DCDA is not only a significant raw material for the N-doped carbon, but also a nitrogen source for the preparation of vanadium nitride. The VN/NC/C-3 catalyst was prepared after optimization of the preparation parameters, and the macro/micro structure demonstrates a superior ORR performance in alkaline media with a positive onset potential of 0.85 V and a half-wave potential of 0.75 V, the limiting current density is as high as 4.52 mA·cm−2, and the Tafel slope is only 75.54 mV·dec−1. The VN/NC/C-3-based Zn–air battery exhibits a highest peak power density (161.82 mW∙cm−2) and an excellent energy density (702.28 mAh·kgZn−1 and 861.51 Wh·kgZn−1). This work provides a valuable synthetic approach for the preparation of other transition metal nitride catalysts with a relative economic value and high performance.