西北农林科技大学

Although N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU) is widely used for kiwifruit enlargement, its effects on post-ripening quality remain unclear. This study integrated physiochemical and multi-omics analyses to investigate the impacts of CPPU on the quality of kiwifruit at harvest and after post-ripening. CPPU promoted fruit enlargement by expanding parenchyma cells, particularly small parenchyma cells, and enhanced uniformity in fruit appearance. CPPU increased pigment content, but suppressed starch accumulation resulting in lower total sugars in post-ripening fruit. Notably, CPPU might accelerate fruit softening by enhancing the activities of polygalacturonase, pectin lyase, and pectin methylesterase, as well as impairing the antioxidant system. CPPU also caused the loss of typical volatile esters (including benzoic acid ethyl ester and ethyl hexanoate), resulting in the dilution of flavor profiles in post-ripening fruit. Multi-omics analysis revealed that CPPU-mediated regulation of ripe fruit quality may be related to two aspects: inhibition of phenylpropanoid biosynthesis and the regulation of amino sugar and nucleotide sugar metabolism. These findings provide new insights into the potential mechanisms by which CPPU regulates the quality of ‘Cuixiang’ kiwifruit.

Observed differences between paddy and upland croplands in soil organic carbon (SOC) and soil inorganic carbon (SIC) may reflect environmental and data-provenance imbalances rather than land-use effects. We reconstructed independent SOC and SIC profile datasets across China, harmonized depths, and separated full-sample comparisons from a prespecified comparable subset. Among all topsoil SOC profiles retained after applying the inclusion criteria (334 paddy, 347 upland), the median Upland-minus-Paddy contrast was −2.12 g kg−1; within the shared subset (97/95), it attenuated to −0.35 g kg−1 (95% interval, −1.74 to 1.55). For 97 paddy soils, changing only the land-use indicator to upland while holding observed soil and environment states fixed yielded a mean SOC contrast of −0.58 g kg−1 (joint 95% interval, −1.02 to −0.15), with 78.4% negative. A layer-resolved Extra Trees S-learner supported this scenario with out-of-fold R2 = 0.72 and mean R2 = 0.72 across ten spatial partitions. The shared topsoil SIC subset retained only 9 paddy and 7 upland profiles, so adjusted SIC could not be estimated. Aridity index (AI) stratification showed the strongest negative SOC contrast in more humid high-AI croplands (−1.08 g kg−1; −1.62 to −0.56), whereas low- and middle-AI strata crossed zero; the high-minus-middle difference was −1.29 g kg−1 (−2.09 to −0.60). Among comparable croplands, observed topsoil SOC differed little between paddy and upland fields, but model predictions indicated lower SOC under upland land use, particularly in humid regions. These results suggest a modest SOC advantage of paddy croplands, while SIC differences remain unresolved.

The non-uniformity of radio frequency (RF) heating is a major technical bottleneck restricting the development of large-scale drying processes for high-moisture agricultural products. To effectively improve the RF heating uniformity of pear slices, this study designed and developed a flipping device suitable for use in an RF heating system. Effects of three key operating parameters, namely electrode gap (100, 110, and 120 mm), hot air temperature (50, 60, and 70 °C), and flipping time interval (15, 30, and 60 min), on drying rate, heating rate, heating uniformity index (λ), and sample colour were systematically investigated. Based on a comprehensive evaluation of drying performance and heating uniformity, the best-performing operating condition within the experimental range was identified as an electrode gap of 110 mm, a hot air temperature of 60 °C, and a flipping time interval of 30 min. Subsequently, comparative tests were conducted among flipping assisted RF drying (HAFRFD), hot air-assisted RF drying (HARFD), hot air and flipping drying (HAFD) and hot air drying (HAD). The results showed that HAFRFD achieved a clearly higher drying rate than the other three drying methods, and its heating uniformity index λ was also significantly lower than that of HARFD, indicating that the introduction of the flipping device effectively improved RF heating uniformity. In addition, pear slices subjected to HAFRFD exhibited the best colour quality. This combined drying method may provide an effective technical solution to address the issues of uneven heating and quality deterioration during RF drying of high-moisture agricultural products.

Fresh hull-removed walnuts are highly susceptible to mildew during storage and efficient preservation technologies are of great significance for the development of the fresh walnut industry. In this study, 'Qingxiang' fresh walnuts were treated by nebulization with 100 mg L⁻¹ arbutin, with untreated walnuts used as the control. Both groups were packaged in 0.04 mm-thick polyethylene modified atmosphere packaging (MAP) and stored at 0 ± 1 °C. Thereafter sensory, key enzyme activities, antioxidant capacity and other quality related parameters were dynamically analyzed during storage. The results showed that the arbutin treatment significantly delayed the onset time of mildew and decreased the mildew incidence, effectively maintained key sensory attributes related to flavor, reduced the generation of volatile organic compounds (VOCs), particularly aldehydes, N-containing compounds and ketones, although it failed to control the increase in sulfur-compounds at the later storage stage. It also enhanced the activities of phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H) and 4-coumarate-CoA ligase (4-CL), but prevented the activities of polyphenol oxidase (PPO), peroxidase (POD) and tyrosinase (TYR), thereby elevated the synthesis and accumulation of phenolic and flavonoid compounds, and antioxidant capacity, consequently inhibited the levels of acid value (AV), peroxide value (PV), and malondialdehyde (MDA), and maintained relatively stable fat content, thereby retained the better quality of fresh walnuts during storage. Arbutin treatment generally suppressed the accumulation of soluble protein and soluble sugar contents of kernels, whereas increased its endogenous arbutin content. These regulatory effects induced by the arbutin treatment were closely associated with the upregulation of JrPAL and Jr4CL expression levels and the downregulation of JrPOD expression levels. In conclusion, 100 mg L⁻¹ arbutin treatment effectively inhibited the mildew growth and kept the quality by activating phenylpropanoid metabolism and subsequently enhancing antioxidant capacity to delay lipid oxidation and membrane damage of fresh walnuts during storage. These findings will provide a theoretical foundation for the application of arbutin in the postharvest preservation of fresh walnuts.

Salinity is a key environmental factor associated with the gut microbiome of the Pacific white shrimp, Litopenaeus vannamei. In this study, metagenomic sequencing was used to investigate gut microbial composition, predicted functional potential, carbohydrate-active enzyme (CAZyme) profiles, and antibiotic resistance gene (ARG) profiles across the salinity gradient from 0 to 30 parts per thousand (ppt). Salinity was associated with marked shifts in microbial community composition. The freshwater group showed higher microbial diversity and enrichment of Rhodobacteraceae-related genera such as Ruegeria and Sedimentitalea, whereas Vibrio was enriched under low-salinity conditions and Enterocytozoon increased under mid- to high-salinity conditions. Functional annotation indicated that the gut microbiome retained a broadly conserved metabolic framework, while specific Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways and CAZyme classes varied across salinity treatments, suggesting salinity-associated changes in predicted microbial functional potential and carbohydrate-utilization capacity. ARG profiles also varied across the salinity gradient and involved multiple resistance categories, including multidrug, β-lactam, aminoglycoside, sulfonamide, rifamycin, and tetracycline resistance. ARG–host association analysis linked representative ARGs to putative bacterial hosts. In particular, Bifidobacterium_adolescentis_rpoB was linked to Bifidobacterium adolescentis and enriched in the freshwater group, whereas TXR and CARB-18 were associated with Vibrio species and were more abundant under saline conditions. Overall, these findings suggest that salinity is an important ecological factor linked to taxonomic structure, predicted functional potential, CAZyme composition, ARG profiles, and putative ARG–host associations in the shrimp gut microbiome.