Transformation of alfalfa chloroplasts and expression of green fluorescent protein in a forage crop

The ability to transform chloroplasts in multiple species is important for improving agricultural traits. Chloroplast transformation of alfalfa (Medicago sativa L.), a useful forage plant with high market value, was achieved using a vector carrying aadA and gfp genes being introduced into the chloroplasts of alfalfa via particle bombardment using leaves and calli as explants. Resistant somatic embryos were generated and developed into plantlets from explants. The transformation efficiency was 1.3% for callus explants and 2.7% for leaf explants. PCR and Southern blotting analyses revealed that the foreign genes were integrated into the transformed chloroplast genome. The occurrence of GFP was further confirmed by fluorescence microscopy. Expression of foreign genes in alfalfa chloroplasts is therefore possible, and provides a novel means for genetic improvement of agronomically important traits and production of value-added proteins.     

Spring migration of the Common Gull in Britain and Ireland

Due to the Collared Dove's extended breeding season, moulting birds may be found in all months. Young birds from late broods often arrest their post-juvenile moult over the midwinter period, and these birds may moult again later in the same year, in line with the moult schedule for adults.     

The genomic composition of Tricepiro, a synthetic forage crop.

Chromosome in situ hybridization (FISH and GISH) is a powerful tool for determining the chromosomal location of specific sequences and for analysing genome organization and evolution. Tricepiro (2n = 6x = 42) is a synthetic cereal obtained by G. Covas in Argentina (1972), which crosses hexaploid triticale (2n = 6x = 42) and octoploid Trigopiro (2n = 8x = 56). Several years of breeding produced a forage crop with valuable characteristics from Secale, Triticum, and Thinopyrum. The aim of this work is to analyse the real genomic constitution of this important synthetic crop. In situ hybridization using total DNA of Secale, Triticum, and Thinopyrum as a probe (GISH) labelled with biotin and (or) digoxigenin showed that tricepiro is composed of 14 rye chromosomes and 28 wheat chromosomes. Small zones of introgression of Thinopyrum on wheat chromosomes were detected. The FISH using the rye repetitive DNA probe pSc 119.2 labelled with biotin let us characterize the seven pairs of rye chromosomes. Moreover, several wheat chromosomes belonging to A and B genomes were distinguished. Therefore, tricepiro is a synthetic hexaploid (2n = 6x = 42) being AABBRR in its genomic composition, with zones of introgression of Thinopyrum in the A genome of wheat.     

Temporal patterns of crop raiding by elephants: a response to changes in forage quality or crop availability?

Temporal patterns of crop raiding by elephants were studied for 13 months in 1996/1997 at Kibale Forest National Park, Uganda. To determine the influence of environmental factors on the timing of raiding, we tested for correlations between crop raiding patterns and the quality of natural forage within the forest as well as crop availability beyond park boundaries. Crop raiding occurred throughout the year with peaks in dry seasons when crop availability was high. Bananas and maize were the main crops raided. Variations in forage quality were moderate with small seasonal fluctuations and peaks in dry seasons. Monthly crop raiding incidences were not influenced by forage quality but by ripening of maize. Comparison of forage quality and temporal distribution of crop raiding between savanna and forest habitats suggests that crop availability is more important in forest habitats, whereas in savanna habitats large seasonal fluctuations in forage quality have a greater influence on temporal patterns of crop raiding.     

生物多样性控制作物病害研究进展

自然资源的合理利用和生态环境保护是人类实现可持续发展的基础, 生物多样性的研究和保护已成为世界各国普遍关注的重大问题。农作物病害是农业生产上重要的生物灾害, 是制约农业可持续发展的主要因素之一, 抗病品种大面积单一化种植导致了农业生物多样性水平严重降低, 因而农业生物多样性的过度丧失已成为可持续农业所面临的主要难题。利用生物多样性持续控制作物病害能减轻作物病害发生和作物产量损失, 达到保护作物多样性, 减少农药过量施用给农业生态环境造成破坏的最终目的, 而揭示生物多样性控制作物病害的机制能有效地指导生产上对不同作物进行合理布局和轮换, 建立作物不同组合的优化搭配和种植模式。文章从分子、生理和生态水平研究农业生物多样性控制作物病害的机制、以及影响作物多样性控制病害的因素、覆盖作物等几方面对生物多样性控制作物病害的研究进展进行概述, 同时对今后生物多样性控制作物病害机制还需加强的研究部分进行了展望。     

Row crop fields provide mid‐summer forage for honey bees

Honey bees provide invaluable economic and ecological services while simultaneously facing stressors that may compromise their health. For example, agricultural landscapes, such as a row crop system, are necessary for our food production, but they may cause poor nutrition in bees from a lack of available nectar and pollen. Here, we investigated the foraging dynamics of honey bees in a row crop environment. We decoded, mapped, and analyzed 3459 waggle dances, which communicate the location of where bees collected food, for two full foraging seasons (April–October, 2018–2019). We found that bees recruited nestmates mostly locally (<2 km) throughout the season. The shortest communicated median distances (0.474 and 0.310 km), indicating abundant food availability, occurred in July in both years, which was when our row crops were in full bloom. We determined, by plotting and analyzing the communicated locations, that almost half of the mid‐summer recruitment was to row crops, with 37% (2018) and 50% (2019) of honey bee dances indicating these fields. Peanut was the most attractive in July, followed by corn and cotton but not soybean. Overall, row crop fields are indicated by a surprisingly large proportion of recruitment dances, suggesting that similar agricultural landscapes may also provide mid‐summer foraging opportunities for honey bees.     

Photobiological control of crop production and plant diseases

Plants, as well as fungi, use ambient sunlight as information to regulate photomorphogenetic processes. The photobiological control of this information showed that the development of photobiological greenhouse plastic covers simulates a photonic information that leads to a physiological enhancement of plant productivity and fungal disease control, thus minimizing the need for the use of agrochemicals. The main characteristics of these photobiological greenhouse plastic covers are the high transmission of photosynthetically active radiation (PAR, 400-700 nm) combined with an increase of the factor zeta = RL(655-665 nm)/FRL(725-735 nm), which affects the cellular phytochromic equilibrium phi = Pfr/(Pfr + Pr) and regulates the photosynthetic activity and therefore the plant productivity. Additionally, increase of the spectral ratios from the transmitted light: BL(420-500 nm)/nearUV(290-370 nm) and BL(420-500 nm)/ FRL(725-735 nm), cause mainly the induction of biochemical, physiological and morphological responses, regulated by cryptochromes in plants (e.g. inflorescence and infructescence) and mycochrome in fungi (e.g. inhibition of sporulation). In the present work, comparative studies with randomly selected greenhouse plastics showed that small changes in the above-mentioned "photobiological" parameters raise the productivity of tomato plants and inhibit the sporulation of several isolates of the fungal pathogen Botrytis cinerea. Thus, a model for the photoregulation of these two phenomena in greenhouses is proposed.     

Five newly-recorded species in the genus Nitzschia from China

When nanodiatoms ( < 20 µm) in the sonthern coastal waters of China were studied using tansmission electron microscopy (TEM), five species in the genus Nitzschia wereidentified new to China. They were N. agnita Hustedt, N. aurariae Cholnoky, N. lacuum H. Lange-Bertalot, N. perspicua Cholnoky and N. pubens Cholnoky.     

Using fungi and yeasts to manage vegetable crop diseases

Vegetable crops are grown worldwide as a source of nutrients and fiber in the human diet. Fungal plant pathogens can cause devastation in these crops under appropriate environmental conditions. Vegetable producers confronted with the challenges of managing fungal pathogens have the opportunity to use fungi and yeasts as biological control agents. Several commercially available products have shown significant disease reduction through various mechanisms to reduce pathogen development and disease. Production of hydrolytic enzymes and antibiotics, competition for plant nutrients and niche colonization, induction of plant host defense mechanisms, and interference with pathogenicity factors in the pathogen are the most important mechanisms. Biotechnological techniques are becoming increasingly valuable to elucidate the mechanisms of action of fungi and yeasts and provide genetic characterization and molecular markers to monitor the spread of these agents.     

Macrothrix flabelligera, a newly-recorded Cladocera Macrothricidae in Brazilian freshwaters.

A short characterization of Macrothrix flabelligera Smirnov, 1992 (Cladocera, Macrothricidae) is presented, following a recent record of this species in Brazil. General aspects and morphological details of the body of parthenogenetic and ephippial females, as well as of males, are described and illustrated.     

Fungi infecting cultivated moss can also cause diseases in crop plants

Bryophytes (mosses) are non‐vascular plants inhabited by a large number of fungal species, but whether mosses can act as reservoirs of fungal pathogens of crop plants has gained little attention. A few moss species including the Sunagoke moss (Racomitrium japonicum; family Grimmiaceae) are found to have modern economical applications in uses such as greening of urban environments. In a previous study, we identified fungi causing symptoms of varying severity in the commercially grown Sunagoke moss. The aim of this study was to test whether the same fungal isolates are pathogenic to vascular plants. An isolate of Fusarium avenaceum lethal to the Sunagoke moss caused root and crown rot in barley (Hordeum vulgare) and reduced germination of tomato (Solanum lycopersicum) and carrot (Daucus carota) grown in the infested soil. An isolate of Cladosporium oxysporum causing mild symptoms in moss reduced growth and caused reddening and premature death of carrot seedlings. On the other hand, isolates of Alternaria alternata and Fusarium oxysporum lethal to the Sunagoke moss caused no detectable symptoms in any tested vascular plant, suggesting specialisation of these isolates to moss. Chloroplast repositioning was observed in the neighbouring cells towards the initially infected cell following infection with F. avenaceum and A. alternata in Physcomitrella patens (family Funariaceae), a model moss used to study microscopic symptoms. Infection of P. patens with a non‐virulent Apiospora montagnei isolate induced formation of papillae in the moss cells, indicating activation of host defence as described in vascular plants. Results suggest that mosses and vascular plants may be linked by a common microbial interface constituted by pathogenic fungi. The findings have epidemiological implications that have gained little previous attention.     

Climate change, interannual weather differences and conflicting responses among crop characteristics: the case of forage quality

Yield and quality of cultivated forage crops are important determinants of animal production efficiency and both forage traits are sensitive to weather. Consequently, it can be presumed that these traits will respond to anticipated changes in the global environment associated with increases in [CO₂] and temperature. Because of the large inter- and intra-annual weather variation that exists in most agricultural regions, it is not clear what the forage production response will be to predicted changes. This uncertainty in forage response to global environment change as compared to interannual weather variation was analysed using a mechanistic simulation model of plant development and growth. The results indicated that low soil-nutrient availability restricts forage production to such a degree that the global environment effects of higher [CO₂] and temperature on quality are essentially irrelevant. When the nitrogen constraint was relaxed, higher [CO₂] caused dry matter and digestibility to increase and protein concentration and leaf:stem ratio to decrease. Increased temperature had opposite effects. The combined effects of [CO₂] and temperature were complex and annual weather variations were dominant, especially in rainfed situations. Limited reliability of predictions of crop response decades into the future indicates that it may be prudent to direct research effort to prepare for a wide range of climatic contingencies.     

Fusarium genomic resources: Tools to limit crop diseases and mycotoxin contamination

It has been almost 10 years since Joan Bennett suggested that fungal biologists create a “wish list” for fungal genome sequences (Bennett JW. White paper: Genomics for filamentous fungi. Fungal Genet Biol 1997; 21: 3–7). The availability of over 200 review papers concerning fungal genomics is a reflection of significant progress with a diversity of fungal species. Although much progress has been made, the use of genomic data to study mycotoxin synthesis and function, pathogenesis and other aspects of fungal biology is in its infancy. Here, we briefly present the status of publicly available genomic resources for Fusarium, a genus of important plant pathogenic and mycotoxin-producing fungi of worldwide concern. Preliminary examination of microarray data collected from F. verticillioides liquid cultures provides evidence of widespread differential gene expression over time.     

基因沉默技术在抗真菌病害中的应用和展望

真菌病害严重威胁作物的产量和品质,给国家和人民造成巨大的经济损失。尤其是引起维管束病害的土传真菌,化学农药的作用效果很不理想。利用抗性基因进行遗传育种是目前生物防治的重要手段之一,但对于缺乏抗性资源的物种,面对强大的土壤真菌病害,研究者也时常束手无策。近年来,利用RNA干扰技术发展而来的宿主诱导的基因沉默(Host induced gene silencing,HIGS)策略,在抗病虫害领域逐渐崭露头角,但由于真菌侵染的复杂多样性及土壤传播的特性,HIGS在土壤真菌病害中的应用充满神秘和挑战。本研究室近期揭示了棉花黄萎病(一种严重的土壤真菌病害)的"罪魁祸首"——大丽轮枝菌的侵染结构和侵染过程;并首次证明了宿主植物内源小RNA能够跨界进入病原菌细胞中降解致病基因表达的抗病作用;在此基础上,本研究室利用HIGS在棉花上获得了对黄萎病抗性较高的品系,成功地开辟了抗土壤黄萎真菌病害的新天地,研究结果显示出基因沉默技术在这一领域强大的应用潜力和前景。     

气候变化对中国农作物病害发生的影响

基于全国农区527个气象站点1961—2010年逐日气象资料、逐年农作物病害发生面积以及产量资料,从气温、降水、日照等角度,采用相关分析方法,研究了气候变化背景下各气象要素变化对中国农作物病害发生的影响。结果表明:近50年来,气候变化导致的各气象因子变化总体有利于病害发生,年平均温度以0.27℃·10a-1的速率升高,其每升高1℃,可导致病害发生面积增加6094.4万hm2次;年平均降雨强度以0.24mm·d-1·10a-1的速度增加,其每增加1mm·d-1,可导致病害发生面积增加6540.4万hm2次;年平均日照时数以47.4h·10a-1的速率减少,其每减少100h,可导致病害发生面积增加3418.8万hm2次;在气候变化导致的光、温、水变化中,温度增加对病害发生面积增加的影响最为显著,其次为日照时数减少、第三为平均降雨强度增大,其标准化回归系数依次为0.508、-0.374、0.112。