激素类除草剂使用方面的新发展

评述了激素类除草剂2,4-滴与麦草畏转基因抗性作物的发展与应用。     

Yield response of maize (Zea mays L.) to crop residue management on two major soil types Of Alemaya, Eastern Ethiopia: I. Effects of varying rates of applied and residual N and P fertilizers

Field trials were conducted on two soil types for seven years (1988–1994) to investigate grain yield response of maize to crop residue application as influenced by varying rates of applied and residual N and P fertilizers. Yearly application of N and P fertilizers at both one-half and full recommended rates resulted in grain yield increases of more than 500 and 1100 kg ha-1, respectively over application of only crop residue. Moreover, grain yield responses due to residual N and P fertilizers applied only during the first year were found to be comparable to the yearly applications of these fertilizers. Rainfall and soil type have exerted considerable influences on the grain yield response obtained in this study. Grain yield exhibited a corresponding decrease with decreasing rainfall. Grain yield increases on Typic Pellustert were relatively higher than on Typic Ustorthent.     

Application of CRISPR/Cas9 in Crop Quality Improvement

The various crop species are major agricultural products and play an indispensable role in sustaining human life. Over a long period, breeders strove to increase crop yield and improve quality through traditional breeding strategies. Today, many breeders have achieved remarkable results using modern molecular technologies. Recently, a new gene-editing system, named the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 technology, has also succeeded in improving crop quality. It has become the most popular tool for crop improvement due to its versatility. It has accelerated crop breeding progress by virtue of its precision in specific gene editing. This review summarizes the current application of CRISPR/Cas9 technology in crop quality improvement. It includes the modulation in appearance, palatability, nutritional components and other preferred traits of various crops. In addition, the challenge in its future application is also discussed.     

转基因抗草甘膦作物的新进展

从推广抗草甘膦大豆以来,抗性大豆、棉花、玉米与油菜非常迅速地发展,与此同时,抗性杂草也开始发生与蔓延,因此,一些公司开始迅速开发既抗草甘膦又抗其它作用机制除草剂的作物,此种多抗性作物给种植者提供控制杂草抗性的措施,并使抗除草剂作物在农业中继续发挥重要作用。     

CHANGES OVER TIME IN THE ALLELOCHEMICAL CONTENT OF TEN CULTIVARS OF RYE (<Emphasis Type="Italic">Secale cereale</Emphasis> L.)

Published studies focused on characterizing the allelopathy-based weed suppression by rye cover crop mulch have provided varying and inconsistent estimates of weed suppression. Studies were initiated to examine several factors that could influence the weed suppressiveness of rye: kill date, cultivar, and soil fertility. Ten cultivars of rye were planted with four rates of nitrogen fertilization, and tissue from each of these treatment combinations was harvested three times during the growing season. Concentrations of a known rye allelochemical DIBOA (2,4-dihydroxy-1,4-(2H)benzoxazine-3-one) were quantified from the harvested rye tissue using high performance liquid chromatography (HPLC). Phytotoxicity observed from aqueous extracts of the harvested rye tissue correlated with the levels of DIBOA recovered in harvested tissue. The amount of DIBOA in rye tissue varied depending on harvest date and rye cultivar, but was generally lower with all cultivars when rye was harvested later in the season. However, the late maturing variety Wheeler retained greater concentrations of DIBOA in comparison to other rye cultivars when harvested later in the season. The decline in DIBOA concentrations as rye matures, and the fact that many rye cultivars mature at different rates may help explain why estimates of weed suppression from allelopathic agents in rye have varied so widely in the literature.     

5种助剂对磺草酮增效作用及其对玉米安全性研究初报

在温室条件下研究了5种常用除草剂助剂油酸甲酯助剂、药笑宝、885、机油乳剂和信德宝对磺草酮防除稗草、牛筋草、马唐、反枝苋、马齿苋和苘麻的药效增强作用以及对玉米苗期生长的安全性。结果表明,5种常用除草剂助剂均不同程度地增加了磺草酮对供试6种杂草的防效,油酸甲酯助剂和药笑宝对磺草酮药效增强作用最大,其次是885和机油乳剂,信德宝的增效作用稍差。而助剂与磺草酮混用后对玉米的安全性由高到低依次是机油乳剂、信德宝、885、药笑宝、油酸甲酯助剂。     

Development of Quorum-Based Anti-Virulence Therapeutics Targeting Gram-Negative Bacterial Pathogens

Quorum sensing is a cell density-dependent signaling phenomenon used by bacteria for coordination of population-wide phenotypes, such as expression of virulence genes, antibiotic resistance and biofilm formation. Lately, disruption of bacterial communication has emerged as an anti-virulence strategy with enormous therapeutic potential given the increasing incidences of drug resistance in pathogenic bacteria. The quorum quenching therapeutic approach promises a lower risk of resistance development, since interference with virulence generally does not affect the growth and fitness of the bacteria and, hence, does not exert an associated selection pressure for drug-resistant strains. With better understanding of bacterial communication networks and mechanisms, many quorum quenching methods have been developed against various clinically significant bacterial pathogens. In particular, Gram-negative bacteria are an important group of pathogens, because, collectively, they are responsible for the majority of hospital-acquired infections. Here, we discuss the current understanding of existing quorum sensing mechanisms and present important inhibitory strategies that have been developed against this group of pathogenic bacteria.     

化学农药的全新机制

介绍一类全新机制的农用抗菌药剂,它们本身并无杀菌活性,但能诱导植物产生系统获得性的抗病性能。最近,这类药剂中的第一个商品已经问世,其活性成分是苯并［１,２,３］噻二唑－７－硫代羧酸（ｓ）甲酯。     

Effect of Land Management in Winter Crop Season on CH4 Emission During the Following Flooded and Rice-Growing Period

A greenhouse pot experiment was carried out to study the effect of land management during the winter crop season on methane (CH₄) emissions during the following flooded and rice-growing period. Three land management patterns, including water management, cropping system, and rice straw application time were evaluated. Land management in the winter crop season significantly influenced CH₄ fluxes during the following flooded and rice-growing period. Methane flux from plots planted to alfalfa (ALE) in the winter crop season was significantly higher than those obtained with treatments involving winter wheat (WWE) or dry fallow (DFE). Mean CH₄ fluxes of treatments ALE, WWE, and DFE were 28.6, 4.7, and 4.1 mg CH₄ m^–2 h^–1 in 1996 and 38.2, 5.6, and 3.2 mg CH₄ m^–2 h^–1 in 1997, respectively. The corresponding values noted with continuously flooded fallow (FFE) treatment were 6.1 and 5.2 times higher than that of the dry fallow treatment in 1996 and 1997, respectively. Applying rice straw just before flooding the soil (DFL) significantly enhanced CH₄ flux by 386% in 1996 and by 1,017% in 1997 compared with rice straw application before alfalfa seed sowing (DFE). Land management in the winter crop season also affected temporal variation patterns of CH₄ fluxes and soil Eh after flooding. A great deal of CH₄ was emitted to the atmosphere during the period from flooding to the early stage of the rice-growing season; and CH₄ fluxes were still relatively high in the middle and late stages of the rice-growing period for treatments ALE, DFL, and FFE. However, for treatments DFE and WWE, almost no CH₄ emission was observed until the middle stage, and CH₄ fluxes in the middle and late stages of the rice-growing period were also very small. Soil Eh of treatments ALE and DFL decreased quickly to a low value suitable for CH₄ production. Once Eh below –150 mV was established, the small changes in Eh did not correlate to changes in CH₄ emissions. The soil Eh of treatments DFE and WWE did not decrease to a negative value until the middle stage of the rice-growing period, and it correlated significantly with the simultaneously measured CH₄ fluxes during the flooded and rice-growing period.     

Effect of Trichilia americana Extract on Feeding Behavior of Asian Armyworm, Spodoptera litura

We investigated the desensitization of Asian armyworms, Spodoptera litura, to a crude methanolic extract of wood Trichilia americana. Following repeated exposures to the extract over four days, desensitization was observed under no-choice conditions at low extract concentration (0.5 g/cm²). No desensitization was observed under choice conditions or at a higher concentration (5.0 g/cm²). Repeated exposures of larvae to the extract over 7.5 hr showed that larvae increasingly tolerated the extract due to hunger, rather than showing true desensitization. When larvae were exposed to the extract in test arenas of different sizes, larvae showed reduced feeding and desensitization as arena size increased. Finally, treatment of whole cabbage plants with extract resulted in larvae abandoning the plant. The crude extract was effective at protecting the plants, although desensitization did not occur, because the larvae moved away from the plant.