Bleeding canker of pear trees is a devastating disease in China. The disease is epidemically emerging prevalently from April to September in pear-growing regions in Zhejiang, Anhui and Shandong provinces of China, and threatening pear industry currently in China. The photo shows the disease damages trunks and branches of pears, resulting in bleeding canker symptoms, which was provided by Prof. Hu Baishi from Nanjing Agricultural University, China. See pages 887–920 in detail.
Chlorophyll (Chl) biosynthesis is essential for photosynthesis and plant growth. A spontaneous mutant cbd1 with Chl biosynthesis deficiency was discovered in paddy field. By map-based gene cloning, it was confirmed that the cbd1 mutation was caused by an mPingA miniature inverted-repeat transposable element (MITE) inserted in the promoter region of Os10g0502400, encoding a glutamyl-tRNA reductase (GluTR). GluTR catalyzes glutamyl-tRNA into glutamate-1-semialdehyde (GSA) and initiates the Chl biosynthesis, which was attenuated by downregulation of OsHemA gene in cbd1 mutant. A leading peptide exists in the N-terminus of GluTR and guides it to chloroplast. GluTR is unique in rice and plays an essential role in photosynthesis. See pages 612–623 for details.
The potato crop is one of the world’s most important food crops, along with rice, wheat, and maize. Potatoes are widely grown over many latitudes and elevations, especially in developing countries such as China. In 2015, China has been boosting potato production to become the fourth major crop produced in the country following rice, wheat and corn, developing potato as the staple food was also included by the Ministry of Agriculture and Rural Affairs of China in its important agenda. Developing potato as the staple food will not only promote the adjustment of planting structure, achieve the sustainable development of agriculture and safeguard China’s national food security, but also improve and enrich the diet structure of Chinese people. Unfortunately, insect pests are one of the major constraints to commercial production of potato in the world. In this special focus, biology, ecology and management for several key insect pests of potato are addressed including potato tuberworm, Phthorimaea operculella Zeller, as shown in the cover photo. This picture was provided by Prof. Zhang Runzhi from Institute of Zoology, Chinese Academy of Sciences.
Tomato was bred from Solanum lycopersicum var. cerasiforme, which was domesticated from Solanum pimpinellifolium (PIM). And dramatic changes in fruit size, flavor, and plant tolerance to abiotic/biotic stresses occurred during domestication and breeding. Gene expression variation bridges this phenotypic variation. To analyze the genetic mechanism of tomato flavor and abiotic/ biotic stresses, we constructed a pan-transcriptome, consisting of 41 265 genes, based on the RNAseq of orange-stage fruit of 399 tomato accessions. Furthermore, 6 122 expression presence/ absence variation (ePAV) genes and 3 629 differentially expressed genes (DEGs) were identified during tomato selection. Finally, 19 genes associated with the reduced total soluble solid (TSS) content in fruit of modern tomato cultivars and two resistance genes were identified differently expressed during domestication. It indicated that natural and artificial selection greatly shaped the tomato transcriptome, thereby altering the fruit TSS content and resistance to abiotic/biotic stresses. The photos are provided by the research team of Prof. Huang Sanwen from Agricultural Genomics Institute, Chinese Academy of Agricultural Sciences. See pages 120–132 for details.
Rice panicle and flower development is of importance to improve yield and quality. The spikelet is a unique flower/panicle structure, however, the molecular mechanisms underlying its development and evolution are still unclear. In the mfs3 mutant, a rice spikelet mutant, the margin region of palea degenerated seriously and an extra floret was produced, suggesting that MFS3 mutation affected both palea identity and spikelet meristem determinacy. By mapping-based clone, it was confirmed that the mfs3 mutation was caused by an 83-bp fragment loss and a base substitution in the LOC_Os06g04540 gene, which encoding an AT-hook DNA-binding protein. It was also found that MFS3 gene might regulate REP1 gene which was involved in the palea development and also influence the expression of meristem determination-related genes, OsMADS1, FON1, SNB and OsIDS1. The photos are provided by the research team of Dr. Li Yunfeng from Southwest University, China. See pages 2673–2681 for details.
Apple stem pitting virus (ASPV) is the type species of the genus Foveavirus, family Betaflexiviridae in the order Tymovirales. The virus can cause different pear diseases. Nowadays, the infection status and molecular characteristics of the virus in old pear trees have never been investigated. ASPV isolate LYC is identified from an over 300-year-old tree of a local Pyrus bretschneideri cultivar ‘Chili’ specifically grown at Laiyang area, Shandong Province, China. ASPV-LYC possesses a chimeric genome harboring a recombination region, is serologically and biologically related to other ASPV isolates. It provides clues for understanding molecular evolution of ASPV. The photo is provided by the research team of Prof. Hong Ni from Huazhong Agricultural University, China. See pages 2549–2560 for details.
Virus-induced gene silencing (VIGS), an appealing reverse-genetic strategy, has been developed as a powerful functional genomics tool to assess gene function for species not amenable to stable genetic transformation. Fusarium head blight (FHB) or scab is a devastating disease of wheat (Triticum aestivum) in humid and warm regions. Previous studies have made some contributions to understand the signal pathways involving in FHB resistance. Jasmonic acid (JA) signaling pathway may mediate FHB resistance in wheat. TaAOC, TaAOS, and TaOPR3 involved in JA signal pathway were selected to assess the potential of Barley stripe mosaic virus (BSMV)-VIGS for gene function analysis on FHB resistance. The plants treated with BSMV:TaAOC, BSMV:TaAOS, or BSMV:TaOPR3 showed more susceptible to FHB compared with BSMV:00 and control, implying their positive regulatory role in FHB resistance. The result indicated that it is feasible to unearth more genes that are positive on FHB resistance by BSMV-VIGS. The photo is provided by the team of Prof. Kong Lingrang from College of Agronomy, Shandong Agricultural University. See pages 2183–2192 for details.
Root-knot nematode (Meloidogyne spp., RKN) resistance to nematicides has become both a local and global threat to producing crops economically in protected agriculture. The combination of a fumigant such as dazomet (DZ) or chloropicrin (CP) and non-fumigating nematicide fosthiazate (FOS) showed a synergistic effect on the control of RKN. This effect mainly due to FOS combined with DZ or CP increased the diffusion rate of FOS across the RKN cuticle. The increase in diffusion rate shortens the time for these pesticides to cause cellular lesions in RKN ultimately leading to increased RKN mortality. Secondly, the fumigant prolongs the half-life of the nematicide FOS in the soil making more of it available for a longer period of time to control RKN. The photo is provided by the team of Prof. Cao Aocheng from Institute of Plant Protection, Chinese Academy of Agricultural Sciences. See pages 2093–2106 for details.
Science and Technology Backyard (STB) is a hub located in rural areas that links the scientific community with smallholder farmers to facilitate information exchange and technology innovation for sustainable intensification. The STB has integrated the power from the government (policies, etc.), industries (products, etc.), universities (knowledge, etc.) and farmer communities (infrastructure, etc.) to empower smallholder farmers. It also provides something new about approach of social service, product design, research and knowledge transfer to the government, industries, universities, and farmer communities, respectively. A typical STB has the following elements: (1) at least one expert (professors, extension workers, etc.); (2) some farmers urgently need advanced technologies; (3) a farmer field school; (4) some field trials; (5) some demonstration fields. The cover shows the key elements and working approach of the STB. Cover photo is provided by Dr. Jiao Xiaoqiang from College of Resources & Environment Sciences, China Agricultural University. The special focus of “Science and Technology Backyard: A novel model for technology innovation and agriculture transformation towards sustainable intensification” addresses the framework and working approach of the STB and its implications for agriculture transformation. See pages 1657–1736 for more details.
The photo is schematic diagram of influenza A virus. The genome of influenza A virus contains eight single-stranded, negative-sense RNA segments that encode at least 10 viral proteins depending on the isolate. Segments 1–6 encode basic polymerase 2 (PB2), polymerase 1 (PB1), acidic polymerase (PA), hemagglutinin (HA), nucleoprotein (NP), and neuraminidase (NA), respectively. Segment 7 encodes the matrix capsid protein 1 (M1) and the matrix capsid protein 2 (M2) through alternate splicing. Segment 8 encodes the non-structural protein (NS1) and nuclear export protein (NS2). Viral ribonucleoprotein (vRNP) complex consists of viral RNA, NP protein and polymerase complex that comprises the PB2, PB1, and PA proteins. The photo is provided by Prof. ZHAO Dongming from Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences. See pages 1419–1472 for details.
Bacterial leaf blight (BLB) and bacterial leaf streak (BLS) caused by Xanthomonas oryzae pv. oryzae (Xoo) and X. oryzae pv. oryzicola (Xoc), respectively, are two important bacterial diseases of rice. The pathogens depend on the transcription activator-like effectors (TALEs) and non-TAL effectors (non-TALEs) to trigger resistance or susceptibility of the host rice. The elucidation of novel molecular mechanism by which TALEs and non-TALEs regulate inner immunity of rice will provide some valuable clues for plant resistance breeding. These photos show the possible molecular mechanisms of Xoc TALEs and non-TALEs disturb inner immunity of rice (1), symptoms of BLB (left) and BLS (right) (2), penetration of Xoc into a stomata of a rice leaf (3), the interaction of Xoc with rice callus cells (4) and the transmission electron micrograph of Xoc cells in the intercellular spaces of the mesophyll parenchyma of a rice leaf (5). The photos were provided by Prof. Ding Xinghua from Shandong Agricultural University, China (1) and Associate Prof. Zou Lifang from Shanghai Jiao Tong University, China (2, 3, 4 and 5), respectively. See pages 1177–1210 in detail.
Cry1Ai-h-loop 2 is a modified protein of Cry1Ai constructed by exchanging loop 2 from Cry1Ah protein and shows insecticidal activity against Helicoverpa armigera. To characterize the key sites of loop 2 in Cry1Ai-h-loop 2, Ala-substituted mutants were generated. The toxicity of these mutants against H. armigera indicated that dual-mutant on Gly373 and Asn375 caused a significant decrease in toxic activity. The reduction of toxicity in the mutant of interest was correlated with decreased binding affinity with midgut brush border membrane vesicles of H. armigera. Taken together with previously reported findings, the progress indicates that the exposed loops are essential for both toxicity and interaction, which could be considered as candidate sites for directional modification of Cry proteins for transgenic crops. See pages 1064–1071 by Liu et al. for more details.
Red imported fire ant Solenopsis invicta has been found in South China since 2003. Currently, S. invicta is found in over 400 counties of 15 provinces in South China, and is a threat to ecosystem, agriculture and human health in invaded areas. We reviewed literatures on S. invicta invasion biology and its impacts on ecosystem structure and function in South China from 2003–2018. The results showed that S. invicta invasion caused arthropod community structure disruption and decreases in diversity and abundance of native ant species. Meanwhile, S. invicta can replace the role of native ants in mutualisms between ants and honeydew-producing Hemiptera, which results in loss of important food resources for native ants and natural enemies of hemipterans. Further research is required to assess the complex ecosystem-level impacts of S. invicta in its introduced regions in large space-scale and long time-scale. Cover photo is provided by Mr. Liu Yan-ming. See pages 788–796 by Wang et al. for more details.
Lycopene is one of the strongest natural antioxidants and the main carotene in ripe tomato. Light is one of the most important environmental stimuli influencing lycopene biosynthesis in tomato study applied supplemental blue and red lighting on tomato plants after anthesis to monitor their effects on lycopene synthesis. The results showed that supplemental blue/red lighting induced higher lycopene content in tomato fruits; the expression of key genes in the lycopene synthesis pathway was induced by supplemental blue/red light. The expression of light signaling components, such as red-light receptor phytochromes (PHYs), blue-light receptor cryptochromes (CRYs) and light interaction factors (PIFs, HY5) were up- or down-regulated by blue/red lighting. Thus, blue and red lights increased lycopene content in tomatoes by inducing light receptors that modulate HY5 and PIFs activation to mediate PSY1 gene expression. These results provide a sound theoretical basis for further elucidation of the light regulating mechanism of lycopene synthesis in tomatoes, and for instituting a new generation of technological innovations for the enhancement of lycopene accumulation in crop production. The photo here shows tomato fruits at different stages under different lights, provided by Prof. Liu Houcheng from College of Horticulture, South China Agricultural University. See pages 590–598 by Xie et al. for more details.
Spatially accurate soil information is critical for precision agriculture, environmental protection and climate mitigation. Unfortunately, the conventional soil maps that were produced by soil survey and traditional mapping techniques, are often inaccessible, coarse and inconsistency at scales, and with limited attribute data. Moreover, these maps require long time in preparation and can hardly be updated over time. Thus, new technologies are urgently needed to fill the gaps between the coarse soil information and the development of data-driven modern agriculture. Digital soil mapping (DSM) is a useful tool to infer the spatial and temporal variations of both qualitative and quantitative soil data in a particular area, and produces maps using related environmental variables. Since last decade, major progresses have been made in different aspects of DSM including soil data sources, predictive models, environmental covariates, and the applications. The Special Focus of “Digital mapping in agriculture and environment” brings together updates on different aspects with focus in agriculture and the environment. Cover photo is provided by Dr. TENG Hong-fen from College of Environmental and Resource Sciences, Zhejiang University, China. See pages 251–264 by Teng et al. for more details.
Somatic embryogenesis (SE) plays a vital role in genetic transformation and massive propagation of important agronomicaland economical crops. In this study, we conducted a systematic assessment of the morphological, cytochemical, and cytogenetical characteristics of six culture strains with various embryogenic/regenerative potential during SE process in cotton. Results indicated that the six cell culture strains had stable ploidy levels, and did not reveal any relationship between the cytogenetic state and their morphogenetic potential. Moreover, the six culture strains were compared via double staining with Evans blue and Acetocarmine to efficiently distinguish embryogenic and nonembryogenic cells and determine the embryogenic nature of the calli. In addition, the kind of auxins added in medium affected not only growth property, color, size of cell clumps but also ploidy level and regeneration ability. By combining analysis of morphological, cytochemical, and cytogenetical characteristics of the cell cultures, we are able to obtain and maintain homogeneous cell population with high morphogenic and regeneration ability and establish efficient somatic embryogenesis and regeneration system from short-term cell cultures in upland cotton, which highlight the application of biotechnological approaches in crop breeding, and above all, to better understand totipotency of cells in higher plants. The photo here shows high-regenerative somatic embryos under light microscope, provided by Prof. Zeng Fanchang from the State Key Laboratory of Crop Biology, Ministry of Science and Technology/College of Agronomy, Shandong Agricultural University, China. See pages 1–8 by Guo et al. in details.