烟草青枯病的病原特性及流行预警

烟草青枯病是当前烟草生产中发生面积大、危害严重、防控困难的土传病害,也是烟草病虫害绿色防控最为关键的流行性病害.作为一种典型的维管束细菌性病害,植株感病属于系统性侵染,条件合适时会突然暴发危害,因此,监测预警十分重要.本文总结了烟草青枯病病原特性、发病症状及病害侵染循环的特点,介绍了影响青枯病发生的关键因子,提出了青枯病的调查与监测预警方法,旨在为烟草青枯病的基础理论研究及有效推进绿色防控提供有力支撑.     

Obstructor,a Frankliniella occidentalis protein,promotes transmission of tomato spotted wilt orthotospovirus

Tomato spotted wilt orthotospovirus (TSWV) causes substantial economic losses to vegetables and other crops. TSWV is mainly transmitted by thrips in a persistent and proliferative manner, and its most efficient vector is the western flower thrips, Frankliniella occidentalis (Pergande). In moving from the thrips midgut to the salivary glands in preparation for transmission, the virions must overcome multiple barriers. Although several proteins that interact with TSWV in thrips have been characterized, we hypothesized that additional thrips proteins interact with TSWV and facilitate its transmission. In the current study, 67 F. occidentalis proteins that interact with G_N (a structural glycoprotein) were identified using a split-ubiquitin membrane-based yeast 2-hybrid (MbY2H) system. Three proteins, apolipoprotein-D (ApoD), orai-2-like (Orai), and obstructor-E-like isoform X2 (Obst), were selected for further study based on their high abundance and interaction strength; their interactions with G_N were confirmed by MbY2H, yeast β-galactosidase and luciferase complementation assays. The relative expressions of ApoD and Orai were significantly down-regulated but that of Obst was significantly up-regulated in viruliferous thrips. When interfering with Obst in larval stage, the TSWV acquisition rate in 3 independent experiments was significantly decreased by 26%, 40%, and 35%, respectively. In addition, when Obst was silenced in adults, the virus titer was significantly decreased, and the TSWV transmission rate decreased from 66.7% to 31.9% using the leaf disk method and from 86.67% to 43.33% using the living plant method. However, the TSWV acquisition and transmission rates were not affected by interference with the ApoD or Orai gene. The results indicate that Obst may play an important role in TSWV acquisition and transmission in Frankliniella occidentalis.     

Effect of bottlegourd seedcoating with antagonists on seedlings,quantum of the pathogen inside the seedlings and population of the soil againstFusarium oxysporum

Bottlegourd seedlings raised from antagonists coated seeds did not show any wilting symptoms and remained completely healthy. The pathogen quantum inside the host tissue was found least. The pathogen propagules per gram of host tissue were restricted and the soil population of theFusarium oxysporum was reduced very much in antagonists introduced soil.     

普通菜豆镰孢菌枯萎病抗性种质资源筛选及全基因组关联分析

普通菜豆镰孢菌枯萎病是严重制约菜豆(Phaseolus vulgaris)产量的主要病害之一。采用下胚轴双孔注射法对601份普通菜豆种质资源进行枯萎病抗性鉴定, 共筛选出4份高抗材料。在此基础上, 基于分布在全基因组上的3 765 456个单核苷酸多态性(SNP)标记, 进行全基因组关联分析, 以P<1×10^-5为阈值。结果检测到57个显著关联的SNP位点, 分布于1、2、6、8和11号染色体上; 共获得8个显著关联区域, 其中位于1号染色体上的区域1包含SNP最多(48个), 最显著SNP P值为2.18E-07。在8个显著关联区域中, 共检测到186个基因, 其中157个基因有注释信息, 编码过氧化物酶、抗病蛋白、转录因子和蛋白激酶等。结合KEGG富集分析和序列同源性比对, 鉴定出9个候选基因可能与抗性相关。     

Effects of deoxynivalenol and zearalenone on oxidative stress and blood phagocytic activity in broilers

Effects of dietary contamination with various levels of deoxynivalenol (DON) and zearalenone (ZEA) were investigated on Ross 308 hybrid broilers of both sexes. After hatching, all chickens were fed an identical control diet for two weeks. Then chickens of Group 1 received a diet contaminated with DON and ZEA, both being 3.4 mg · kg^?1, while Group 2 received DON and ZEA at 8.2 and 8.3 mg · kg^?1, respectively. The diet of the control group contained background levels of mycotoxins. Samples of blood and tissues were collected after two weeks. Intake of both contaminated diets resulted in a significantly decreased activity of glutathione peroxidase (GPx) and increased level of malondialdehyde (MDA) in liver tissue, while in kidneys the concentration of MDA was significantly increased only in Group 1. On the other hand, activities of blood GPx and plasma γ-glutamyltransferase (GGT) were elevated in Group 2 only. Activities of thioredoxin reductase in liver and GPx in duodenal mucosa tissues, superoxide dismutase (SOD) in erythrocytes as well as levels of MDA in duodenal mucosa and α-tocopherol in plasma were not affected by dietary mycotoxins. Blood phagocytic activity was significantly depressed in Group 1 and 2. These results demonstrate that diets contaminated with DON and ZEA at medium levels are already able to induce oxidative stress and compromise the blood phagocytic activity in fattening chickens.     

Linking physiological parameters with visible/near-infrared leaf reflectance in the incubation period of vascular wilt disease

The photosynthetic pigments are mainly responsible for absorbing the light intended to promote photosynthesis on the chloroplast of the leaves. Different studies have related the spectral response in the leaves of plants with the biotic stress generated by pathogens. In general, maximum differences in reflectance have been found in the range of 380–750 nm between plants subjected to biotic stress and healthy plants. In this study, it was possible to characterize and relate the spectral variance in leaves of S. lycopersicum infected with F. oxysporum with this physiological variation and pathogen concentration in tomato plants during the asymptomatic period of vascular wilt. Photosynthetic parameters derived from gaseous exchange analysis in the tomato leaves correlated related with four bands in the visible range (Vis). Additionally, five specific bands also present a high correlation with the increase in the concentration of F. oxysporum conidia measured at the root: 448–523 nm, 624–696 nm, 740–960 nm, 973–976 nm, and 992–995 nm. These wavelengths allowed a 100% correct classification of the plants inoculated with F. oxysporum from the plants subjected to hydric stress and the control plants in the asymptomatic period of the disease. The spectral response to biotic and abiotic stress in the measured Vis/NIR range can be explained by the general tendency to change the concentration of chlorophyll and carotene in tomato leaves. These studies also highlight the importance of the implementation of robust multivariate analysis over the multiple univariate analysis used in the applied biological sciences and specifically in the agricultural sciences. These results demonstrate that specific wavelength responses are due to physiological changes in plants subjected to stress, and can be used in indexes and algorithms applied to the early detection of diseases in plants on different pathosystems.     

Conservation biology of the succulent shrub,Euphorbia barnardii,a serpentine endemic of the Northern Province,South Africa

Euphorbia barnardii White, Dyer & Sloane is a relatively small, succulent shrub found in the Northern Province of South Africa. In 1994 it was listed as endangered by the Transvaal Threatened Plants Programme, because only three populations, totalling 1150 plants, were found. However, our study found five populations totalling 10 783 plants (9503 were reproductive). One population, found 50 km from the others, in the Bewaarkloof district, differs in terms of habitat type and morphology and may therefore be a different taxon. The other populations occur in Sekhukhuneland. Soil analyses showed that E. barnardii is restricted to ultramafic (serpentine) substrates. A sample of 2015 plants was examined in 1995 for size, stage, new growth, dead branches, reproduction (indices of vigour), damage and disease. Analysis of the results of 10 years’ demographic monitoring (1985–1995) on two of the Sekhukhuneland populations showed that one population, which was vigorous in 1995, showed little change in population size and structure, while the other, which had low vigour in 1995, showed a precipitous decline to local extinction in the monitoring plot. Aerial photographs taken in 1957 (1963 for Bewaarkloof) and 1986 showed large increases in human population density within 1.5 km of the E. barnardii populations except at Bewaarkloof, where it decreased. An increase in human habitation is associated with an increase in livestock (mostly cattle and goats) which trample plants. Trampling damages the terminal segments, which may lead to lowered reproductive output and increase susceptibility to opportunistic bacterial wilt pathogens. Bacterial wilts were prevalent on all populations but were particularly high at Bewaarkloof and on the population that showed a steep decline in numbers. Disease incidence was associated with the level of plant damage. The impact on plants further up the slopes and on the crest of hills (quite far from human settlements) was to a far lesser degree but further increases in human population density could change this situation. While this study has shown that the population size of E. barnardii is much greater than previously thought, the species is still threatened by several different processes and should be listed as ‘Vulnerable (A1a + c, B1, B2b + e, C1, D2)’ according to World Conservation Union categories.