Bud dormancy is a complex physiological process of perennial woody plants living in temperate regions, and it can be affected by various phytohormones.  Cytokinin oxidase/dehydrogenases (CKXs) are a group of enzymes essential for maintaining cytokinin homeostasis, yet a comprehensive analysis of these enzymes in peach remains lacking.  Here, a total of 51 CKX members from different species, including six from peach, eleven from apple, nine from poplar, seven from Arabidopsis, eight from strawberry, and ten from rice, were identified using the Simple HMM Search tool of TBtools and a BLASTP program and classified into four groups using phylogenetic analysis.  Conserved motif and gene structure analysis of these 51 CKX members showed that 10 conserved motifs were identified, and each CKX gene contained at least two introns.  Cis-element analysis of PpCKXs showed that all PpCKX genes have light-responsive elements and at least one hormone-responsive element.  The changed relative expression levels of six PpCKX genes in peach buds from endodormancy to bud-break were observed by qRT-PCR.  Among them, the expression trend of PpCKX6 was almost opposite that of PpEBB1, a positive bud-break regulator in woody plants, around the bud-break stage.  Y1H, EMSA, and dual-luciferase assays indicated that PpEBB1 negatively regulated PpCKX6 through direct binding to a GCC box-like element located in the promoter region of PpCKX6.  In addition, a transient assay showed that overexpression of PpCKX6 delayed the bud-break of peach.  These results indicate that the PpCKX genes play an essential role in the dormancy-regrowth process, and PpCKX6 may act downstream of PpEBB1 directly to regulate the bud-break process, which further improves the hormone-regulatory network of dormancy-regrowth of woody plants, and provides new insights for molecular breeding and genetic engineering of peach.

A high-efficiency mode of high-low seedbed cultivation (HLSC) has been listed as the main agricultural technology to increase land utilization ratio and grain yield in Shandong Province, China.  However, limited information is available on the optimized water and nitrogen management for yield formation, especially the grain-filling process, under HLSC mode.  A three-year field experiment with four nitrogen rates and three irrigation rates of HLSC was conducted to reveal the response of grain-filling parameters, grain weight percentage of spike weight (GPS), spike moisture content (SMC), and winter wheat yield to water and nitrogen rates.  The four nitrogen rates were N1 (360 kg ha^–1 pure N), N2 (300 kg ha^–1 pure N), N3 (240 kg ha^–1 pure N), and N4 (180 kg ha^–1 pure N), respectively, and the three irrigation quotas were W1 (120 mm), W2 (90 mm), and W3 (60 mm), respectively.  Results showed that the determinate growth function generally performed well in simulating the temporal dynamics of grain weight (0.989<R²<0.999, where R² is the determination coefficient).  The occurrence time of maximum filling rate (T_max) and active grain-filling period (AGP) increased with the increase in the water or nitrogen rate, whereas the average grain-filling rate (G_mean) had a decreasing trend.  The final 1,000-grain weight (FTGW) increased and then decreased with the increase in the nitrogen rates and increased with the increase in the irrigation rates.  The GPS and SMC had a highly significant quadratic polynomial relationship with grain weight and days after anthesis.  Nitrogen, irrigation, and year significantly affected the T_max, AGP, G_mean, and FTGW.  Particularly, the AGP and FTGW were insignificantly different between high seedbed (HLSC-H) and low seedbed (HLSC-L) across the water and nitrogen levels.  Moreover, the moderate water and nitrogen supply was more beneficial for grain yield, as well as for spike number and grain number per hectare.  The principal component analysis indicated that combining 240–300 kg N ha^–1 and 90–120 mm irrigation quota could improve grain-filling efficiency and yield for the HLSC-cultivated winter wheat.