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The irrigation method of partial root-zone drying (PRD) is based on drought stimulation without real water stress in order to induce xerophytophysiological signalling and regulations. In the present study, a series of measurements with potato (Solanum tuberosum L.) crops were conducted to understand the mechanisms underlying PRD. The results showed that PRD-induced osmotic adjustment shown by lower osmotic potential and higher turgor potential in fully turgid leaves and higher symplastic water fraction in cells. The PRD-induced osmotic adjustment was also confirmed by the active accumulation of osmolytes such as free proline, soluble sugars and soluble proteins. In PRD-treated potato plants, turgor maintenance by osmotic adjustment ensured improvements in photosynthetic activities, plant growth and final tuber yield. One of the signal substances, superoxide (O2−), was increased by PRD but soon eliminated by superoxide dismutase (SOD), which was activated by PRD along with catalase (CAT) and peroxidase (POD). As one of the stress-responsive genes, the aquaporin gene RD28 was upregulated by PRD and might explain the improved physiological activities associated with the abovementioned xerophytophysiological regulations.

Phytoplasmas are cell wall-less prokaryotic pathogens causing many plant diseases with various host plants, widely geographical distribution and adverse impacts on economics and environments. Abundant genetic diversity of the phytoplasmas has been evidenced by vast researches. In the paper, we conducted a comparatively systematic and comprehensive schematic review and comment on the research status of phy- toplasma genetic diversity. We discussed the potential research directions with respect to research technology and generation mechanism of phytoplasmal genetic variation as well as relationships to pathogenicity in fu- ture. Analysis on five phytoplasmas whose whole genomes have been completed has indicated the definite genetic variation in size, structure and function of phytoplasmal genomes, which lack many genes for stan- dard metabolic functions. There are different number, size and function of the plasmids in various phyto- plasma strains. Two copies of ribosomal RNA operons among all the phytoplasmas showed significant varia- tion which provided the present foundation for classification and identification of phytoplasmas. Studies on protein-encoding genes, such as ribosomal protein (rp), elongation factors (tuf and fusA), translocation pro- teins (secY and secA), effector molecules as well as non-encoding sequences such as promoters and pseu- dogenes have further revealed the rich genetic diversity of phytoplasmas. Since inadequate information is known regarding the characteristics of morphology, cultivation, physiology and metabolism due to the diffi- •综述•

Plant residues are viewed as an important source for organic matter in farmlands. We studied if wheat straw and weed residues applied to an organically managed cabbage field by favoring alternative prey may improve the suppression of lepidopteran pests by indigenous generalist predators. The trophic characteristics of predators were determined by a stable isotope approach (δ13C and δ15N). The relative contribution of alternative prey in predators species' (i.e. wolf spiders) diet was estimated using a mixed model based on their stable isotope signatures. As expected, densities of alternative prey became significantly higher in the plots with added plant residues. Consequently, population densities of predators (wolf spiders, predacious carabids and Japanese tree frogs) also became relatively higher and pest densities lower in these plots. We also note that, besides lepidopteran pests, alternative prey accounted for approximately 80% of predator diets. This finding suggests that they may play an important ...

Natural farming (NF), an environmentally friendly agricultural practice similar to organic farming, was developed in Japan. Unlike conventional farming, little is known about the influence of NF on soil microbial communities, especially the surface soil. We therefore compared the effect of seven years&rsquo, conventional practice (CP), conventional practice without chemicals (CF), and NF on soil properties and microbial community structure at two soil depths (0&ndash, 10, 10&ndash, 20 cm) in an experimental cabbage field. Both soil depth and agricultural practice significantly influenced edaphic measures and microbial community structure. NF improved bulk density, pH, electrical conductivity, urease activity, and nitrate reductase activity in topsoil, similar trends were observed in deeper soil. Pyrosequencing demonstrated that the use of pesticides in conventional farming (CP) led to lower microbial abundance and diversity in topsoil than CF. Similarly, NF increased microbial abundance compared to CP. However, distinct taxa were present in the topsoil, but not deeper soil, in each treatment. CP-enriched microbial genera may be related to plant pathogens (e.g., Erwinia and Brenneria) and xenobiotic degraders (e.g., Sphingobacterium and Comamonas). The microbial community structure of NF was distinct to CP/CF, with enrichment of Pedomicrobium and Solirubrobacter, which may prefer stable soil conditions. Network analysis of dominant genera confirmed the more stable, complex microbial network structure of the 0&ndash, 10 cm than 10&ndash, 20 cm layer. Flavisolibacter/Candidatus Solibacter and Candidatus Nitrososphaera/Leuconostoc are potentially fundamental taxa in the 0&ndash, 10 cm and 10&ndash, 20 cm layer networks, respectively. Overall, we show that NF positively affects soil quality and microbial community composition within sustainable farming systems.

Recent research using Arabidopsis has shown that blue light stimulates the plant through the receptor protein and induces regulations physiologically and morphologically. It is important to know whether the theory can be used in food crop production. In the present study blue light emitted from light-emitting diodes (LED) was used as a stimulus to tomato crop canopy after sunset for 2 h to induce xerophytophysiological regulations. Blue (450 nm), white and red (660 nm) LED lamps, all with a properties of 0.48 W, 24 V, and 45 μmol m2 s−1 at 10 cm over the lamp, were compared with non-illumination control. A 2 × 4 two factor experiment was conducted in a randomized split block design with the two cultivars as the main block. Results showed that the osmotic potential in the symplasm at full turgor was lower and the leaf turgor potential at full turgor was higher in tomato leaves in blue light treatment. The water fraction in the symplasm in the leaf was larger or the apoplastic water fraction was smaller in leaf of blue light irradiated plants. Both osmotic potential and relative water content at the point of incipient plasmolysis were lower in tomato leaves in blue light treatment. More leaf water was lost by stomatal transpiration and less leaf water was lost by cuticular transpiration in leaves of blue light treated tomato plants. Fruit color was improved and redder in blue light treatment. Fruit yield was increased by all light illumination treatments. The damage of fruit caused by Helicoverpa armigera worms was more severely in red light treatment and less severely in blue and white light treatments compared with the control. The leaf blight index was lower in blue and white light illumination treatments than the red light treatment and the control. Both cultivars showed LED illumination responses similar to each other although fruit yield was lower and leaf blight was severer in ‘Baiju’ than in ‘Myoko’. In conclusion, illumination treatment with blue light from LED as a stimulus was effective in fruit yield increase and quality improvement as well as improvement in disease resistance of the tomato crop.

Partial root zone drying (PRD) has been used as a technique in the production of many crops. However, the extent or duration of the drying treatment would change the effect and the mechanisms in terms of plant water relations are not clear enough. The aim of this research was to evaluate the PRD effect with shorter or longer drying duration in a potato crop and elucidate the mechanisms based on plant water relations. Potato (Solanum tuberosum L. cv. May Queen) was grown in experimental plots under plastic rainout shelters. Three treatments: (1) whole-season PRD, (2) early-season PRD for 8 weeks and then return to normal irrigation for the remainder of the season and (3) normal irrigation as control, were arranged in a Latin square design in 9 plots. Water was supplied by drip irrigation to one side of the potato row once every 5 days on average, and the other side of the row was allowed to dry for 15 days, and then the irrigation line was moved to the dry side and the wet side allowed to dry. Pressure–volume curves were used to analyze the osmotic adjustment induced by PRD and a modified mathematic equation, − Ψ − 1 = Ψ FT − 1 − π s + a − 1 [ ζ 0 − β ( 1 − ζ ) − ζ ap ] e − α ( 1 − ζ ) + π s + a − 1 [ ζ 0 − β ( 1 − ζ ) − ζ ap ] was used to compare the pressure–volume relations. As shown by the results, tuber yield and photosynthetic activity were increased by the early-season PRD treatment, but not by the whole-season PRD treatment because the whole-season PRD treatment reduced the leaf area index. By analyzing the pressure–volume curves, it was found that osmotic adjustment occurred and the turgor potential was higher in potato leaves in the PRD treatments. The fraction of water in the cell symplasm was higher and that in apoplasm was smaller in PRD-treated potato leaves. Both the osmotic potential and relative water content at the point of incipient plasmolysis were lower in potato leaves in the PRD treatments, suggesting that the plants in the PRD plots were more resistant to water stress, which was also confirmed by the analysis of transpiration declining curve of excised leaves. In conclusion, the PRD treatment was effective in improving potato tuber yield, but early-season treatment rather than the whole-season treatment should be adopted.

Jujube witches' -broom (JWB) is an important plant disease caused by phytoplasma. The major objective of our research was to classify JWB in Beijing and Hebei districts and to provide reference for classification in subgroup level.By use of PCR, the elongation factor Tu (tuf gene) and ribosomal protein (rp) gene of phytoplasma associated with JWB in Beijing and Hebei districts were amplified separately with universal primer pairs fTufu/rTufu and rp(v)F1A/rp(v) R1A. Partial tuf gene and rp gene were sequenced and similarity analysed with other phytoplasmas.We obtained partial tuf gene sequence (824bp) and complete rp gene (1196bp) from the diseased sample. In tuf gene, JWB in Beijing shared most similarity (92.84%) with Flavescence dorée (FD) phytoplasma (Candidatus Phytoplasma vitis), however, shared a low similarity (57.29%) with JWB in Shaanxi district which had been already reported. The similarity analysis for sequences of rp gene showed a high identity (96%) with members of the 16SrV group phytoplasmas. It shared most identity (99.83%) with JWB strain Taishan and Hemp fiber witches' -broom phytoplasma (HFWB) of the 16SrV group.The JWB strains in Beijing and Hebei are members of 16Sr V; JWB in Beijing and Hebei share high similarity, and show a diversity with JWB in Shaanxi.

Jujube witches'-broom is an important disease in jujube cultivation areas, which causes serious losses in jujube fruit production. To understand the genetic variability and diversity of jujube witches'-broom phytoplasma population from the different cultivars and various regions of China.We collected 32 samples from 14 cultivars or wild sour jujubes in 7 regions of China and detected them with PCR with the primers R16mF2/R16mR1 for phytoplasma 16S rDNA, SR1/SR for 16S-23SrRNA space region (SR) and FD9f/r for secretion proteins (secY). The direct sequencing of PCR products and sequencing by cloned PCR products were used for sequence polymorphism and phylogenetic analyses by comparison to the databases of known conserved gene sequences.We detected phytoplasmas by PCR amplification of 16SrDNA from all the diseased jujube samples. All the phytoplasma isolates infected various jujube cultivars belonged to subgroup 16SrV-B of elm yellows group and had closer homology with Bischofia polycarpa witches'-broom and cherry lethal yellows phytoplasmas occurred in China than other 16SrV phytoplasmas in other countries. The sequence polymorphism at different extent in 16SrDNA, SR and secY gene and genetic diversity were revealed in phytoplasma strain population related to different habitats, among which the dominant strains were always detected by the direct sequencing of PCR products in all the diseased areas of China. The degree of variability on secY gene of collected phytoplasma strains was greater than that of 16SrDNA and SR sequences, and some base substitutions could not alter encoded amino acid, however certain single base deletions detected in a Shandong and a Beijing strains may have impact on the gene structure or function.Phytoplasma strains from different cultivars and regions show dramatic genetic diversity. Compared with direct sequencing of PCR products, the sequencing by cloning PCR products was more useful for the displaying of variants and phylogeny in phytoplasma strain population.