Effects of converting natural grasslands into planted grasslands on ecosystem respiration: a case study in Inner Mongolia,China

With increasingly intensifying degradation of natural grasslands and rapidly increasing demand of high quality forages, natural grasslands in China have been converted into planted grasslands at an unprecedented rate and the magnitude of the conversion in Inner Mongolia is among the national highest where the areal extent of planted grasslands ranks the second in China. Such land-use changes(i.e., converting natural grasslands into planted grasslands) can significantly affect carbon stocks and carbon emissions in grassland ecosystems. In this study, we analyzed the effects of converting natural grasslands into planted grasslands(including Medicago sativa, Elymus cylindricus, and M. sativa+E. cylindricus) on ecosystem respiration(F_(eco)) in Inner Mongolia of China. Diurnal F_(eco) and its components(i.e., total soil respiration(F_(ts)), soil heterotrophic respiration(F_(sh)) and vegetation autotrophic respiration(F_(va))) were measured in 2012(27 July to 5 August) and 2013(18 July to 25 July) in the natural and planted grasslands. Meteorological data, aboveground vegetation data and soil data were simultaneously collected to analyze the relationships between respiration fluxes and environmental factors in those grasslands. In 2012, the daily mean F_(eco) in the M. sativa grassland was higher than that in the natural grassland, and the daily mean F_(va) was higher in all planted grasslands(i.e., M. sativa, E. cylindricus, and M. sativa+E. cylindricus) than in the natural grassland. In contrast, the daily mean F_(ts) and F_(sh) were lower in all planted grasslands than in the natural grassland. In 2013, the daily mean F_(eco), F_(ts) and F_(va) in all planted grasslands were higher than those in the natural grassland, and the daily mean F_(sh) in the M. sativa+E. cylindricus grassland was higher than that in the natural grassland. The two-year experimental results suggested that the conversion of natural grasslands into planted grasslands can generally increase the F_(eco) and the increase in F_(eco) is more pronounced when the plantation becomes more mature. The results also indicated that F_(sh) contributed more to F_(eco) in the natural grassland whereas F_(va) contributed more to F_(eco) in the planted grasslands. The regression analyses show that climate factors(air temperature and relative humidity) and soil properties(soil organic matter, soil temperature, and soil moisture) strongly affected respiration fluxes in all grasslands. However, our observation period was admittedly too short. To fully understand the effects of such land-use changes(i.e., converting natural grasslands into planted grasslands) on respiration fluxes, longer-term observations are badly needed.     

Identification of the molecular make-up of the Potato virus Y strain PVY(Z): genetic typing of PVY(Z)-NTN

Potato virus Y (PVY) strains were originally defined by interactions with different resistance genes in standard potato cultivars. Five distinct strain groups are defined that cause local or systemic hypersensitive responses (HRs) in genetic background with a corresponding N gene: PVY(O), PVY(N), PVY(C), PVY(Z), and PVY(E). The nucleotide sequences of multiple isolates of PVY(O) and PVY(N) differ from each other by ≈8% along their genomes. Additionally, complete genome sequences of multiple recombinant isolates are composed of segments of parental PVY(O) and PVY(N) sequences. Here, we report that recombinant isolate PVY-L26 induces an HR in potato 'Maris Bard' carrying the putative Nz gene, and is not recognized by two other resistance genes, Nc and Ny(tbr). These genetic responses in potato, combined with the inability of PVY-L26 to induce vein necrosis in tobacco, clearly define it as an isolate from the PVY(Z) strain group and provide the first information on genome structure and sequence of PVY(Z). The genome of PVY-L26 displays typical features of European NTN-type isolates with three recombinant junctions (PVY(EU-NTN)), and the PVY-L26 is named PVY(Z)-NTN. Three typical PVY(NTN) isolates and two PVY(N) isolates, all inducing vein necrosis in tobacco, were compared with PVY-L26. One PVY(NTN) isolate elicited HR reactions in Maris Bard, similar to PVY-L26, while two induced a severe systemic HR-like reaction quite different from the quasi-symptomless reaction induced by two PVY(N) isolates. 'Yukon Gold' potato from North America produced HR against several PVY(NTN) isolates, including PVY-L26, but only late and limited systemic necrosis against one PVY(N) isolate. Consequently, according to symptoms in potato indicators, both PVY(Z) and PVY(NTN) isolates appeared biologically very close and clearly distinct from PVY(O) and PVY(N) strain groups.     

Identification of Random Amplified Polymorphic DNA Markers Linked to the Co-4 Resistance Gene to Colletotrichum lindemuthianum in Common Bean

ABSTRACT New cultivars of the common bean (Phaseolus vulgaris) with durable resistance to anthracnose can be developed by pyramiding major resistance genes using marker-assisted selection. To this end, it is necessary to identify sources of resistance and molecular markers tightly linked to the resistance genes. The objectives of this work were to study the inheritance of resistance to anthracnose in the cultivar TO (carrying the Co-4 gene), to identify random amplified polymorphic DNA (RAPD) markers linked to Co-4, and to introgress this gene in the cultivar Rudá. Populations F(1), F(2), F(2:3), BC(1)s, and BC(1)r from the cross Rudá x TO were inoculated with race 65 of Colletotrichum lindemuthianum, causal agent of bean anthracnose. The phenotypic ratios (resistant/susceptible) were 3:1 in the F(2) population, 1:1 in the BC(1)s, and 1:0 in the BC(1)r, confirming that resistance to anthracnose in the cultivar TO was monogenic and dominant. Six RAPD markers linked to the Co-4 gene were identified, four in the coupling phase: OPY20(830C) (0.0 centimorgan [cM]), OPC08(900C) (9.7 cM), OPI16(850C) (14.3 cM), and OPJ01(1,380C) (18.1 cM); and two in the repulsion phase: OPB03(1,800T) (3.7 cM) and OPA18(830T) (17.4 cM). OPY20(830C) and OPB03(1,800T), used in association as a codominant pair, allowed the identification of the three genotypic classes with a high degree of confidence. Marker OPY20(830C), which is tightly linked to Co-4, is being used to assist in breeding for resistance to anthracnose.     

Responses of water productivity to irrigation and N supply for hybrid maize seed production in an arid region of Northwest China

Water and nitrogen(N) are generally two of the most important factors in determining the crop productivity. Proper water and N managements are prerequisites for agriculture sustainable development in arid areas. Field experiments were conducted to study the responses of water productivity for crop yield(WP_(Y-ET)) and final biomass(WP_(B-ET)) of film-mulched hybrid maize seed production to different irrigation and N treatments in the Hexi Corridor, Northwest China during April to September in 2013 and also during April to September in 2014. Three irrigation levels(70%–65%, 60%–55%, and 50%–45% of the field capacity) combined with three N rates(500, 400, and 300 kg N/hm~2) were tested in 2013. The N treatments were adjusted to 500, 300, and 100 kg N/hm~2 in 2014. Results showed that the responses of WP_(Y-ET) and WP_(B-ET) to different irrigation amounts were different. WP_(Y-ET) was significantly reduced by lowering irrigation amounts while WP_(B-ET) stayed relatively insensitive to irrigation amounts. However, WP_(Y-ET) and WP_(B-ET) behaved consistently when subjected to different N treatments. There was a slight effect of reducing N input from 500 to 300 kg/hm~2 on the WP_(Y-ET) and WP_(B-ET), however, when reducing N input to 100 kg/hm~2, the values of WP_(Y-ET) and WP_(B-ET) were significantly reduced. Water is the primary factor and N is the secondary factor in determining both yield(Y) and final biomass(B). Partial factor productivity from applied N(PFP_N) was the maximum under the higher irrigation level and in lower N rate(100–300 kg N/hm~2) in both years(2013 and 2014). Lowering the irrigation amount significantly reduced evapotranspiration(ET), but ET did not vary with different N rates(100–500 kg N/hm~2). Both Y and B had robust linear relationships with ET, but the correlation between B and ET(R~2=0.8588) was much better than that between Y and ET(R~2=0.6062). When ET increased, WP_(Y-ET) linearly increased and WP_(B-ET) decreased. Taking the indices of Y, B, WP_(Y-ET), WP_(B-ET) and PFP_N into account, a higher irrigation level(70%–65% of the field capacity) and a lower N rate(100–300 kg N/hm~2) are recommended to be a proper irrigation and N application strategy for plastic film-mulched hybrid maize seed production in arid Northwest China.     

Viruses in the northern potato-producing regions of Saudi Arabia

Agar double diffusion tests and, later, ELISAs were used to detect viruses associated with potato in 242 samples collected in 16 trips to Tabuk and Hail, northern regions of Saudi Arabia, in four consecutive growing seasons (autumn 1989, spring and autumn 1990 and spring 1991). Eleven different viruses were detected in Tabuk and 12 in Hail. The viruses detected in Tabuk were alfalfa mosaic (AMV), cucumber mosaic (CMV), tobacco mosaic (TMV), potato leaf roll (PLRV), tomato spotted wilt (TSWV), tobacco ringspot (TRSV) and potato A, M, S, X and Y. The same viruses, plus potato yellow dwarf (PYDV), were detected in Hail. AMV was most frequently and CMV least frequently detected in Tabuk, whereas in Hail the most and least common were PVA and PLRV respectively.     

Identification of the principal viruses infecting tomato crops in Tunisia

Serological tests have been used to detect viruses associated with tomato in 257 samples collected in different regions in Tunisia, Cap-Bon, Sahel and South during successive seasons. The viruses detected were cucumber mosaic cucumovirus (CMV) and tomato aspermy cucumovirus (TAV), potato Y potyvirus (PVY), tobacco etch potyvirus (TEV) and pepper veinal mottle potyvirus (PVMV), tomato mosaic tobamovirus (ToMV) and tobacco mosaic tobamovirus (TMV), tobacco rattle tobravirus (TRV), alfalfa mosaic alfamovirus (AMV), tomato spotted wilt tospovirus (TSWV), tomato ringspot nepovirus (TomRSV) and potato X potexvirus (PVX). Some were detected in all three regions surveyed, at variable frequencies: TMV, CMV, TEV, PVY, ToMV, AMV, TAV, TSWV and TRV. Others were only detected in two regions (PVMV in Cap-Bon and Sahel and PVX in Sahel and in the south) or one region (TomRSV in Cap-Bon). Movement of individual viruses from one region to another may be due to movement of specific vectors, as in the case of the thrips-transmitted TSWV moving from the south to the north. Some of these viruses were found for the first time in Tunisia.     

A quantitative review of tebuconazole effect on fusarium head blight and deoxynivalenol content in wheat

ABSTRACT A meta-analysis of the effect of tebuconazole (e.g., Folicur 3.6F) on Fusarium head blight and deoxynivalenol (DON) content of wheat grain was performed using data collected from uniform fungicide trials (UFTs) conducted at multiple locations across U.S. wheat-growing regions. Response ratios (mean disease and DON levels from tebuconazole-treated plots, divided by mean disease and DON levels from untreated check plots) were calculated for each of 139 studies for tebuconazole effect on Fusarium head blight index (IND; field or plot-level disease severity, i.e., mean proportion of diseased spikelets per spike) and 101 studies for tebuconazole effect on DON contamination of harvested grain. A random-effects meta-analysis was performed on the log-transformed ratios, and the estimated mean log ratios were transformed to estimate the mean (expected) percent control for IND ( C(IND) ) and DON ( C(DON)). A mixed effects meta-analysis was then done to determine the effects of wheat type (spring versus winter wheat) and disease and DON levels in the controls on the log ratios. Tebuconazole was more effective at limiting IND than DON, with C(IND) and C(DON) values of 40.3 and 21.6%, respectively. The efficacy of tebuconazole as determined by the impact on both IND and DON was greater in spring wheat than in winter wheat (P < 0.01), with a 13.2% higher C(IND) and a 12.4% higher C(DON) in spring wheat than in winter wheat. In general, C(IND) and C(DON) were both at their lowest values (and not significantly different from 0) when mean IND and DON in the controls, respectively, were low (相似文献   

Occurrence,sources, and relationships of soil microplastics with adsorbed heavy metals in the Ebinur Lake Basin,Northwest China

There is a lack of research on soil microplastics in arid oases considering the rapid economic development of northwestern China. Here, we studied the occurrence and sources of microplastics in soil, as well as the relationships between microplastics and adsorbed heavy metals in the Ebinur Lake Basin, a typical arid oasis in China. Results showed that (1) the average microplastic content in all soil samples was 36.15 (±3.27) mg/kg. The contents of microplastics at different sampling sites ranged from 3.89 (±1.64) to 89.25 (±2.98) mg/kg. Overall, the proportions of various microplastic shapes decreased in the following order: film (54.25%)>fiber (18.56%)>particle (15.07%)>fragment (8.66%)>foam (3.46%); (2) among all microplastic particles, white particles accounted for the largest proportion (52.93%), followed by green (24.15%), black (12.17%), transparent (7.16%), and yellow particles (3.59%). The proportions of microplastic particle size ranges across all soil samples decreased in the following order: 1000-2000 µm (40.88%)>500-1000 µm (26.75%)>2000-5000 µm (12.30%)>100-500 µm (12.92%)>0-100 µm (7.15%). FTIR (Fourier transform infrared) analyses showed that polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polyethylene (PE), and polystyrene (PS) occurred in the studied soil; (3) random forest predictions showed that industrial and agricultural production activities and the discharge of domestic plastic waste were related to soil microplastic pollution, in which agricultural plastic film was the most important factor in soil pollution in the study area; and (4) seven heavy metals extracted from microplastics in the soil samples showed significant positive correlations with soil pH, EC, total salt, N, P, and K contents (P<0.01), indicating that these soil factors could significantly affect the contents of heavy metals carried by soil microplastics. This research demonstrated that the contents of soil microplastics are lower than other areas of the world, and they mainly come from industrial and agricultural activities of the Ebinur Lake Basin.     

准噶尔盆地南部农区野生饲用植物资源研究

为了解准噶尔盆地南部农区野生饲用植物资源,调查研究了该区域野生饲用植物的科属组成及其生活型和生态型特点,并对其适口性和营养价值进行了分析。结果表明：该区共有野生饲用植物34科145属214种,优势科有禾本科(38属71种)、藜科(18属22种)、菊科(15属21种)、豆科(14属19种)、苋科(8属11种)、十字花科(8属10种);生活型植物以草本植物(1～2年生124种,多年生62种)为主,占86.92%,木本植物有28种,占13.08%;生态型植物以中生为主(183种)。依据适口性可将该区野生饲用植物划分为优、良、中、低4个等级,其中优等95种、良等77种、中等36种、低等6种。营养成分丰富且适口性较好的饲用植物主要集中在禾本科(21种)、豆科(17种)和藜科(13种)。     

Sequence tagged site markers to rsp1, rsp2, and rsp3 genes for resistance to septoria speckled leaf blotch in barley

ABSTRACT Five random amplified polymorphic DNA markers, two in coupling (OPAH5(545C), and OPBA12(314C)) and three in repulsion phase (UBC285(158R), OPC2(441R), and OPB17(451R)), closely linked to Rsp genes conferring resistance to Septoria speckled leaf blotch (SSLB), were identified using bulked segregant analysis in three F(2) populations, each containing a Rsp gene. These markers were converted into the sequence tagged site (STS) markers SUBC285, SOPC2, SOPAH5, and SOPBA12. Another STS marker (MWG938) linked to Rsp2 in coupling phase was also identified in an F(2) population from the cross Robust/CIho 4780. The STS markers were tested on a set of 42 resistant and susceptible barley germplasm lines and 98 landraces. The expected sizes of marker fragments associated with each allele at Rsp loci were present in resistant or susceptible accessions. Efficiency of marker-assisted selection (MAS) for Rsp1, Rsp2, and Rsp3 using STS markers were evaluated in three F(23) populations in the greenhouse and the field. Results of testing F(23) progeny demonstrated that the accuracy of MAS was, with one exception, greater than 97% in the greenhouse and in two field locations (90% in the Osnabrock, ND trial for Rsp2). The STS markers closely linked to Rsp genes also identified the SSLB resistance corresponding to Rsp1, Rsp2, or Rsp3 in gene pyramiding F(2) populations. The STS markers tightly linked to Rsp genes may be useful for M and for pyramiding with other genes in barley breeding for SSLB resistance.     

中国甘薯病毒种类的血清学和分子检测

 2009～2010年,从我国18个省（市）采集了176份表现病毒病症状的甘薯样品。利用血清学、PCR和核苷酸序列测定的方法,对上述样品中的病毒种类进行了鉴定。血清学检测结果表明,供试样品中甘薯羽状斑驳病毒（SPFMV）的阳性率最高,达56.3%,其次为甘薯G病毒（SPVG）和甘薯类花椰菜花叶病毒(SPCaLV),阳性率分别为34.1%和33.5%。PCR和核苷酸序列测定结果表明,我国甘薯上至少存在SPFMV、SPVG、甘薯潜隐病毒（SPLV）、甘薯褪绿斑病毒（SPCFV）、甘薯褪绿矮化病毒（SPCSV）、黄瓜花叶病毒（CMV）、甘薯脉花叶病毒（SPVMV）和甘薯卷叶病毒（SPLCV）8种病毒。此外,供试样品中没有检测出甘薯轻斑驳病毒（SPMMV）,是否存在甘薯轻斑点病毒(SPMSV)、SPCaLV和C 6病毒尚不能确定。     

Inheritance of beta-cypermethrin resistance in the housefly Musca domestica (Diptera: Muscidae)

BACKGROUND: Beta-cypermethrin, a synthetic pyrethroid insecticide, was applied frequently in the control of health pests including houseflies, Musca domestica L., in China. However, different levels of resistance to beta-cypermethrin were monitored in field strains of houseflies. A strain of M. domestica, 4420-fold resistant to beta-cypermethrin after continuous 25 generations of selection, was used in this paper to determine the mode of inheritance of pyrethroid resistance. RESULTS: The estimated realized heritability (h(2)) of beta-cypermethrin resistance was 0.30 in this resistant strain. Results of bioassays showed no significant difference in values of LD(50) and slope of log dose-probit lines between reciprocal progenies F(1) and F'(1), and yielded values of - 0.10 (F(1)) and - 0.11 (F'(1)) for the degree of dominance (D). Chi-square analysis from responses of self-bred and backcross progenies (F(2), BC(1) and BC(2) respectively) indicated that the null hypothesis, a single gene responsible for resistance, was accepted. The minimum number of independent segregation genes was 0.93 for F(1) by Lande's method. CONCLUSION: It was concluded that beta-cypermethrin resistance in the housefly was inherited as a single, major, autosomal and incompletely recessive factor. These results would provide the basic information for pest management programmes.     

甘肃省季节性干旱综合指数的特征

利用甘肃省71个气象站1971-2013年月降水量资料,借助Z指数构建了基于干旱频率、干旱强度的干旱综合指数评价指标,从季节性干旱以及季节性连旱着手分析了不同时间尺度的干旱特征。结果表明:研究区季节性趋旱程度(MK0)和趋旱范围(DR,%)差异显著,其中春季陇东高原为-0.154(100%),重旱为灵台(-0.238*)、宁县(-0.180)、镇原(-0.178);夏季河西走廊为-0.081(73.7%),重旱为马鬃山(-0.271*)、安西(-0.255*)、敦煌(-0.171);秋季陇中高原为-0.017(50.9%),重旱在会宁(-0.186)。季节性干旱综合指数重旱时段显示,春季为1995年(陇东0.481),夏季为1997年(陇南0.405),秋季为1972年(甘南0.366),冬季为1998年(陇东0.586)和2009年(甘南0.449)。两季连旱高值区在白银、会宁、古浪、玛曲、灵台、永登、华池、静宁等地(0.030),其中秋冬连旱最为严重(0.0274);三季连旱高值区为会宁、古浪、静宁、白银、永登等地(0.020),其中夏秋冬连旱最为显著(0.017 5);四季连旱高值区为会宁、古浪、西峰、灵台、泾川等地(0.015),即除了冬春夏秋连旱外,其余季节性连旱程度均比较显著(0.009)。     

Effect of ginger supplementation on developmental toxicity induced by fenitrothion insecticide and/or lead in albino rats

Evaluation of the antioxidant and antiteratogenic role of ginger Zingiber officinale polyphenols against the toxicity induced by fenitrothion and/or lead in female albino rats were investigated. Adult virgin females were divided into 8 groups and were orally treated as follow: control (C), 1% w/w of ginger (G), 120 μg/animal lead as lead acetate (L), 10 mg/kg of fenitrothion (F), lead (120 μg/animal) fenitrothion (10 mg/kg) (LF), ginger (1%w/w) + fenitrothion (10 mg/kg) (GF), ginger (1%w/w) + lead (120 μg/animal) (GL), ginger (1%w/w) + lead (120 μg/animal) + fenitrothion (10 mg/kg) (GLF). Treatments were expanded for 28 days before pregnancy and during gestation period from zero to 6th day. Blood samples were taken at the day 20th of gestation and animals were sacrificed to investigate the effect of tested substances on dams and development of their fetuses. Inhibition in AchE in (F) and (LF) groups and elevation in plasma AchE in (L) groups were observed. Elevation in oxidative stress biomarker malondialdehyde (MDA) was recorded in all intoxicated groups concomitants with reduction in total reduced glutathione (GSH) and reduction in the activity of glutathione S-transferase (GST). Elevation in liver function biomarkers alanin amintransferase (ALT) and aspartate aminotransferase (AST) and reduction in plasma total protein and albumin were recorded in (F), (L) and (LF). Supplementation with ginger in diet attenuates the alteration in MDA, GSH, GST, ALT and AST, however, it failed to counteract the effect of F, L and LF on AchE, total protein and albumin. Significant alterations in maternal toxicity were recorded in (GF, GL, LF and GLF) compared with control group. Also, parameters of embryotoxicity and fetotoxicity indicated significant decrease in litter number that observed in F and L and the number of dead fetus/dam and litters number increased in L group. Supplementation with ginger decreased each of the number of died fetus, growth retardation and fetal length, while, it increased fetal weight. As regards to, teratological aspects, the percentage of skeletal malformations and visceral anomalies were observed in all feti obtained from treated groups with different percentages. Supplementation with ginger slightly attenuates the developmental toxicity of fenitrothion and/or lead.     

大黑和暗黑蛴螬危害花生的防治指标研究

花生种苗期大黑蛴螬和花生生长期大黑、暗黑蛴螬的虫口密度(X)与减产率(Y)呈明显的直线正相关,其相关式苗期网池接虫为Y=0.7245 0.004X±3.3957(r=0.9520,n=39);同步模拟为Y=0.4452 0.0040X±1.3959(r=0.9661,n=28);接虫示范为Y=0.1360 0.0074X±1.5888(r=0.9800,n=4);生长期接大黑金龟甲卵为Y=1.2927 0.0042X±3.2704(r=0.8993,n=36);接暗黑金龟卵为Y=0.7308 0.0042X±2.1344(r=0.9568,n=32)。研究分析提出花生种苗期防治指标为三龄大黑蛴螬每平方米2头;生长期防治指标为每平方米大黑卵3粒,暗黑卵5粒。     

Evidence for oxidative stress involved in physiological leaf spot formation in winter and spring barley

ABSTRACT A leaf spot disease with unknown etiology has become more pronounced in spring and winter barley in Germany in recent years. The symptoms are similar to net blotch and Ramularia leaf spots, but the causal agents of these diseases are not identified. The symptom expression varied much on cultivars. Cultivars most affected by the disease of both spring and winter barley showed a significantly higher level of superoxide (O(2) ) production and lipid peroxidation (malondialdehyde), but a lower level of antioxidant potential expressed as superoxide dismutase (SOD) activity, catalase activity, and integral water-soluble antioxidant capacity (ACW) than insensitive cultivars. A high positive correlation between O(2) production and leaf spot development between ear emergence and milk ripeness was established in the most sensitive winter barley cv. Anoa (r(2) = 0.9622) and spring barley cv. Barke (r(2) = 0.9434). Leaf H(2)O(2) levels increased with the severity of leaf spots. The histochemical localization of O(2) and H(2)O(2) in the tissues adjacent to leaf spots indicated that these two active oxygen species (AOS) are involved in the formation of leaf spots. Reduction of symptom severity by applying strobilurin and azole fungicides was always associated with elevated SOD activity and ACW content and suppressed O(2) production. However, peroxidase activities were significantly higher in sensitive cultivars and in more severely affected tissues and decreased by applying fungicides. Thus, it is assumed that a possible genetic mechanism based on the imbalanced AOS metabolism contributes to formation of physiological leaf spots.     

Viruses and virus diseases of grapevine in Tunisia

Mature canes were collected from vines in the main grapevine-growing areas in Tunisia (Cape Bon, Bizerte, Ben Arous), from commercial vineyards and mother-plant plots, to assess the presence of virus and virus-like diseases. Biological (mechanical transmission onto herbaceous hosts and grafting onto indicator woody plants) and serological detection (ELISA) methods were applied. ELISA showed that 96.4% of 669 vines tested were infected, most of them (88.1%) by at least two viruses. Grapevine leafroll-associated 3 closterovirus (GLRaV-3) was the most widespread virus (87.9%), followed by grapevine A vitiviras (GVA, 69.4%), grapevine fleck virus (GFkV, 51.9%), grapevine leafroll-associated 1 closterovirus (GLRaV-1, 36.8%), grapevine leafroll-associated 2 closterovirus (GLRaV-2, 19.1%), grapevine fan leaf nepovirus (GFLV, 18.2%) and grapevine B vitiviras (GVB, 14.8%). ELISA tests yielded negative results for grapevine leafroll-associated 7 closterovirus (GLRaV-7) and potato X potexvirus (PVX). The highest infections were found in Bizerte and Cape Bon regions (100 and 99.2%), and in vineyards aged over 20 years (98.5%) as compared with the younger ones (81.1%). Rootstocks in mother-plant plots were practically free from all the viruses tested (1 plant infected out of 81), whereas severe infections were found in Vitis vinifera mother plants (67.4% of 341 samples), in particular table grapes (92.6%) compared with wine grapes (47.9%). In these mother-plant plots, the prevailing viruses were GLRaV-3 (41.3%), followed by GFkV (36.7%), GVA (27.9%), GLRaV-1 (17%) and GLRaV-2 (15.2%). GFLV and GVB were far more limited (1.5 and 0.6%, respectively). The presence of vein necrosis and vein mosaic was ascertained by transmission onto 110R and Vitis riparia indicators, whereas only GFLV was mechanically transmitted onto herbaceous hosts (from about 20% of the samples).     

Tank-mix adjuvants and pesticide residues: some regulatory and quantitative aspects

Although it is well known that judicious use of adjuvants can increase the performance of foliage-applied sprays of many agrochemicals, little information is available in the public domain about their ultimate effects on pesticide residues in treated crops. In the present work, the influence of Agral (polyoxyethylene nonylphenols), Toil (methyl esters of rapeseed fatty acids) and Bond (styrene-butadiene copolymers) on surface and crop residues of diclofop-methyl/diclofop and propiconazole in wheat and field beans was investigated using a model system simulating field practice. Pesticides were applied as commercial formulations, diclofop-methyl 378 g litre(-1) EC (Hoegrass) and propiconazole 250 g litre(-1) EC (Tilt), at their maximum approved rates, 1135 g AI ha(-1) and 125 g AI ha(-1), respectively, both in the presence or absence of the maximum rate recommended for each candidate adjuvant. No detectable residues of diclofop-methyl or propiconazole were found in wheat 35 days after any of the four applications. However, residues of diclofop were present in this crop, and those from applications containing Agral (0.07 mg kg(-1) fresh weight (FW)) or Bond (0.08 mg kg(-1) FW) were significantly lower than those with no adjuvant (0.14 mg kg(-1) FW) or Toil (0.16 mg kg(-1) FW). Unlike wheat, residues of both diclofop and propiconazole were detected in field beans after harvest. Significantly higher residues of the former were recorded from the applications with Agral or Bond (ca 0.32 mg kg(-1) FW) than with those with no adjuvant or Toil (ca 0.15mg kg(-1) FW). All the propiconazole applications containing adjuvants showed a similar significant increase in residues (0.10-0.16 mg AI kg(-1) FW) over the no-adjuvant treatment (0.05 mg kg(-1) FW) in this crop. There appeared to be little agreement between the apparent amounts of uptake, as indicated by the rates of decline of surface residues up to 5 days after application, and final residues in either target species. On wheat, surface residues of diclofop-methyl decreased from initially ca 20 to as little as 0.02 mg kg(-1) FW using adjuvants; the corresponding values for propiconazole were ca 2 to ca 0.03 mg kg(-1) FW. Recoveries of diclofop-methyl from the surfaces of field beans were much higher than those from wheat, declining from ca 30 to only ca 6 mg kg(-1) FW during the course of 5 days; the corresponding residues for propiconazole were ca 2 mg to 0.15 mg kg(-1) FW. These findings are discussed in relation to uptake results obtained with radiolabelled pesticides and adjuvants in the laboratory, and to the mandatory requirements for pesticide residue data for the authorised use of adjuvants in the UK.     

Germination of Seeds of Cirsium arvense (L.) Scop.

Cirsium arvense (L.) Scop. is a persistent and troublesome weed which reproduces vegetatively. Establishment from seeds (achenes) is considered negligible under natural conditions in the United Kingdom (Bates, 1946), although germination under normal farm conditions was found to be good in America (Hansen, 1918). Korsmo (1930) in Norway and Hayden (1934) in Iowa found that the seeds had no dormancy period, but Niethammer (1934) and Zilke (1967) recorded seed dormancy in Germany and South Dakota respectively. An examination was therefore made of some of the factors which may regulate the germination of seeds of C. arvense in this country.     

Diffusion and emissions of 1,3-dichloro propene in Florida sandy soil in microplots affected by soil moisture, organic matter, and plastic film

The main objective of this study was to determine the influence of soil moisture, organic matter amendment and plastic cover (a virtually impermeable film, VIF) on diffusion and emissions of (Z)- and (E)-1,3-dichloropropene (1,3-D) in microplots of Florida sandy soil (Arredondo fine sand). Upward diffusion of the two isomers in the Arredondo soil without a plastic cover was greatly influenced by soil-water content and (Z)-1,3-D diffused faster than (E)-1,3-D. In less than 5 h after 1,3-D injection to 30 cm depth, (Z)- and (E)-1,3-D in air dry soil had diffused to a 10 cm depth, whereas diffusion for the two isomers was negligible in near-water-saturated soil, even 101 h after injection. The diffusion rate of (Z)- and (E)-1,3-D in near-field-capacity soil was between the rates in the two water regimes. Yard waste compost (YWC) amendment greatly reduced diffusion of (Z)- and (E)-1,3-D, even in air-dry soil. Although upward diffusion of (Z)- and (E)-1,3-D in soil with VIF cover was slightly less than in the corresponding bare soil; the cover promoted retention of vapors of the two isomers in soil pore air in the shallow subsurface. More (Z)-1,3-D vapor was found initially in soil pore air than (E)-1,3-D although the difference declined thereafter. As a result of rapid upward movement in air-dry bare soil, (Z)- and (E)-1,3-D were rapidly volatilized into the atmosphere, but emissions from the near-water-saturated soil were minimal. Virtually impermeable film and YWC amendment retarded emissions. This study indicated that adequate soil water in this sandy soil is needed to prevent rapid emissions, but excess soil water slows diffusion of (Z)- and (E)-1,3-D. Thus, management for optimum water in soil is critical for pesticidal efficacy and the environment.