Improved Cold and Drought Tolerance of Doubled Haploid Maize Plants Selected for Resistance to Prooxidant tert‐Butyl Hydroperoxide

To improve the abiotic stress tolerance of maize (Zea mays L.), doubled haploid (DH) plants were produced by in vitro selection of microspores exposed to tert‐butyl hydroperoxide (t‐BuOOH) as a powerful prooxidant This study investigated the tolerance of the progenies of t‐BuOOH‐selected DH lines to oxidative stress, cold and drought in controlled environment pot experiments by analyses of photosynthetic electron transport and CO₂ assimilation processes, chlorophyll bleaching and lipid peroxidation of leaves. Our results demonstrated that the t‐BuOOH‐selected DH plants exhibited enhanced tolerance not only to oxidative stress‐induced by t‐BuOOH but also to cold and drought stresses. In addition, they showed elevated activities of antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, catalase, glutathione reductase and glutathione S‐transferase when compared with the DH lines derived from microspores that were not exposed to t‐BuOOH and to the original hybrid plants. The results suggest that the simultaneous up‐regulation of several antioxidant enzymes may contribute to the oxidative and cold stress tolerance of the t‐BuOOH‐selected DH lines, and that the in vitro microspore selection represents a potential way to improve abiotic stress tolerance in maize.     

Is there a relationship between haemoglobin genotype and the innate resistance to experimental Haemonchus contortus infection in Merino lambs?

Responses to a single or repeated infection with 7000 infective larvae of Haemonchus contortus were studied in an experiment using a total of 106 3-month-old lambs with AA, AB or BB haemoglobin (Hb) genotypes. Results were assessed by faecal egg counts, adult worm counts, haematocrit values, haemoglobin concentrations, total serum protein and serum antibody IgG1 and IgA ELISA titres. None of these parameters showed a strong relationship to the Hb type. The prevalence of low responder (greater than 500 worms) and of high responder (less than 50 worms) animals in groups AA, AB and BB Hb types was 3.8 and 34.6, 20.6 and 35.2, 28.1 and 43.7%, respectively, suggesting that the responsiveness to nematode infection is under the control of gene(s) not closely linked with those determining the Hb genotype. Worm counts of a primary infection are more subject to variation than those of a secondary infection. There is a strong relationship between adult worm counts and faecal egg counts taken close to the time of slaughter. In living animals low and high responder discrimination can be based on individual faecal egg counts around 50 days after a secondary infection. Haematocrit values proved to be of little value in the low and high responder selection. In this regard neither Hb concentration nor total serum protein values are of practical significance. In 3-month-old lambs primary infection induced partial immunity which could prevent the establishment of a part of the secondary infection, irrespective of the presence or absence of the primary worm population. The development of immunity was not associated with an increase of serum IgG1 and IgA antibody levels. Specific antibody production was not influenced by Hb types. Mean antibody levels of low responder lambs showed no difference from those of high responders. Thus, serum IgG1 and IgA levels are of no predictive value in identifying lambs which are genetically resistant to Haemonchus infection.     

Prevalence of Setaria equina microfilaraemia in horses in Hungary

Peripheral blood samples were collected randomly from 195 horses in various parts of Hungary, and the presence of microfilariae was evaluated by the Knott technique. On the basis of morphological identification 18 of the horses (9.2 per cent) were infected with Setaria equina, and the infection was confirmed in 10 animals by pcr and sequencing. The level of microfilaraemia was between 1 and 1138 larvae in 2 ml of blood. There was no correlation between the time of sampling or the sex of the animals (stallions versus mares) and the prevalence of infection, but the prevalence decreased with age. There was a significant association between the prevalence of microfilaraemia and the presence of still waters; positive samples were collected either in the region of Lake Balaton, the largest lake in the country, or at places with nearby ponds.     

转基因抗虫棉对农户生产行为的影响分析

以河北主产棉区340个农户2002-2003年的问卷调查和关键人物访谈为依据,分析了转基 因抗虫棉对农户生产行为的影响。结果表明,转基因抗虫棉的应用影响或改变了农户的植棉意向、抗 虫棉种子选择,棉田害虫防治及植棉技术需求等生产行为。     

Prevalence of intestinal parasites in dogs in some urban and rural areas of Hungary

A total of 490 canine faecal specimens collected in the eastern and northern regions of Hungary were examined for helminth eggs. From the results it appears that more than 50% of the dogs were infected with at least one parasite species. The prevalence of eggs (%) in the two regions was as follows: Toxocara canis (24.3-30.1); Trichuris vulpis (20.4-23.3); Ancylostomatidae (8.1-13.1); Capillaria spp. (0-7.3); Toxascaris leonina (2.1-0); Taenia-type (2.8-2.4); Dipylidium caninum (0.4-1); coccidia (3.5-3.4). Of the positive dogs, 8.5-18.1% harboured two or more species of parasites. The prevalence of parasitic infection was also evaluated according to the maintenance, feeding, and age of the animals. The significance of zoonotic diseases (echinococcosis, toxocarosis, ancylostomatidosis) caused by intestinal helminths makes it necessary to know the infection status of domestic dogs and to take measures for control.     

Environmental change, hillslope erosion and suspended sediment: Some observations from Hong Kong

Evidence of environmental change in Hong Kong, including vegetation, climate and the frequency of hillfires is presented. Hillfires may be an important influence upon slope degradation in the territory. Field observations made in the Northwest New Territories provide evidence that hillfires increase soil erosion on slopes and result in higher storm-period concentrations of suspended sediment. Monitoring carried out in a small drainage basin reveals that landslides deliver sediment to an upland stream giving very high concentrations and affecting sediment properties, with the C and N content declining under the influence of landslides. Should environmental change alter the frequency of landsliding and hillfire on natural terrain in Hong Kong this will have implications for hillslope degradation and sediment transport in upland streams.     

Effectiveness and chemical pest control of Bt-cotton in the Yangtze River Valley, China

The paper determines what might be the factors beneath the limited or reduced effectiveness being observed in China. The analysis is based on the data collected for several years from many locations in the Yangtze River Valley Varietal Experiment Network. All varieties declared to be Bt-cotton were confirmed to have the Bt-gene, the expression of which was assessed in three ways: through the analysis of Bt-protein production and through indoor and outdoor bioassays. Gene expression varied substantially between varieties and between years for the few varieties which were tested in two subsequent years. The Bt-cotton varieties being sown cannot control bollworms totally and this led to spray chemicals regardless of the real infestation level. Farmers are hence paying high prices for varieties which are not totally resistant to bollworms and pest control costs are not reduced to the extent that they might expect, lowering the profitability of cotton production.     

The Application of GGE Biplot Analysis for Evaluating Test Locations and Mega-Environment Investigation of Cotton Regional Trials

In the process to the marketing of cultivars, identification of superior test locations within multi-environment variety trial schemes is of critical relevance. It is relevant to breeding organizations as well as to governmental organizations in charge of cultivar registration. Where competition among breeding companies exists, effective and fair multi-environment variety trials are of utmost importance to motivate investment in breeding. The objective of this study was to use genotype main effect plus genotype by environment interaction（GGE） biplot analysis to evaluate test locations in terms of discrimination ability, representativeness and desirability, and to investigate the presence of multiple mega-environments in cotton production in the Yangtze River Valley（YaRV）, China. Four traits（cotton lint yield, fiber length, lint breaking tenacity, micronaire） and two composite selection indices were considered. It was found that the assumption of a single mega-environment in the YaRV for cotton production does not hold. The YaRV consists of three cotton mega-environments： a main one represented by 11 locations and two minor ones represented by two test locations each. This demands that the strategy of cotton variety registration or recommendation must be adjusted. GGE biplot analysis has also led to the identification of test location superior for cotton variety evaluation. Although test location desirable for selecting different traits varied greatly, Jinzhou, Hubei Province, China, was found to be desirable for selecting for all traits considered while Jianyang, Sichuan Province, China, was found to be desirable for none.     

N2O emissions from an irrigated and non‐irrigated organic soil in eastern Canada as influenced by N fertilizer addition

Drainage and cultivation of organic soils often result in large nitrous oxide (N₂O) emissions. The objective of this study was to assess the impacts of nitrogen (N) fertilizer on N₂O emissions from a cultivated organic soil located south of Montréal, QC, Canada, drained in 1930 and used since then for vegetable production. Fluxes of N₂O were measured weekly from May 2004 to November 2005 when snow cover was absent in irrigated and non‐irrigated plots receiving 0, 100 or 150 kg N ha⁻¹ as NH₄NO₃. Soil mineral N content, gas concentrations, temperature, water table height and water content were also measured to help explain variations in N₂O emissions. Annual emissions during the experiment were large, ranging from 3.6 to 40.2 kg N₂O‐N ha⁻¹ year⁻¹. The N₂O emissions were decreased by N fertilizer addition in the non‐irrigated site but not in the irrigated site. The absence of a positive influence of soil mineral N content on N₂O emissions was probably in part because up to 571 kg N ha⁻¹ were mineralized during the snow‐free season. Emissions of N₂O were positively correlated to soil CO₂ emissions and to variables associated with the extent of soil aeration such as soil oxygen concentration, precipitation and soil water table height, thereby indicating that soil moisture/aeration and carbon bioavailability were the main controls of N₂O emission. The large N₂O emissions observed in this study indicate that drained cultivated organic soils in eastern Canada have a potential for N₂O‐N losses similar to, or greater than, organic soils located in northern Europe.