Insecticidal control of cereal aphids and its impact on the epidemiology of the barley yellow dwarf luteoviruses

Imidacloprid is a seed-applied nitroguanidine insecticide that has both contact and long-lasting systemic properties. Its direct effects on cereal aphid populations and indirect effects on barley yellow dwarf luteovirus (BYDV) incidence were examined in laboratory and field studies. Adult longevity and fecundity of three aphid species caged on various aged, imidacloprid-treated oat or wheat plants was reduced, although the quantitative efficacy of the compound differed among aphid species. The transmission efficiency of BYDV by aphids to imidacloprid-treated plants was lower, relative to nontreated plants, when plants were 10 days old, but similar to nontreated when plants were 24 days old. In three years of field trials using winter wheat and two years using spring oat, aphid populations were reduced significantly in imidacloprid-treated plots relative to nontreated plots. Although the number of alighting alate aphids did not differ significantly between imidacloprid-treated or nontreated plots, the number of apterous aphids remained significantly lower in the treated plots for the majority of the growing season. BYDV epidemics did not develop in spring oat in either of the two years. BYDV epidemics did develop in the fall in the emerging winter wheat crop. Rhopalosiphum maidis was the predominant aphid migrating into the 1991–1992 crop. The incidence of the BYDV-RMV serotype was three times higher in nontreated plots than in imidacloprid-treated plots. In the 1992–1993 and 1994–1995 seasons, R. maidis and R. padi were the predominant aphids migrating into the crop, although R. padi was the predominant colonizing aphid. The incidence of BYDV-RMV was similar in imidacloprid treated and nontreated plots in 1992–1993, but the incidence of the BYDV-PAV serotype was significantly less in the treated plots. In 1994–1995, the incidence of both BYDV-PAV and BYDV-RMV was higher in the nontreated plots than in the imidacloprid-treated plots. Imidacloprid offers several advantages both in terms of its long-lasting systemic activity and its mode of applicaiton. As a seed treatment, the amount of material applied is minimized, there is little waste and the environmental impacts are reduced. The effectiveness of the compound at reducing the fecundity or reproductive rate of several aphid species may be advantageous in controlling secondary spread of viruses. However, the contact properties of the compound, important in repelling aphids or preventing phloem feeding, may be short-lived, thus reducing its effectiveness in preventing primary spread of the virus into the crop, especially under high aphid and inoculum pressure.     

The effect of combined infestation by cereal aphids (Macrosiphum avenae (Fabr.) (Sitobion avenae) and Rhopalosiphum padi (L.)) and cereal leaf beetles (Oulema melanopus (L.)) on their population development and on yield of winter wheat

Previous clarification of the relationships between insect populations and damage by cereal pests has enabled the effect of combined pest infestation on the yield of winter wheat to be analysed more thoroughly. The cereal aphids Macrosiphum avenae (Fabr.) (Sitobion avenae) and Rhopalosiphum padi (L.), each in combination with the cereal leaf beetle Oulema melanopus (L.), were investigated in pot trials which enabled interactions between the combined pest populations to be studied also. Although intraspecific competition was observed for each pest population, there was no interspecific adverse effect of density on population increase. With increasing population densities of the pests in combination, the relative contribution of each species to the combined yield losses decreased. Consequently, there was no summation of individual losses, but a reduction of up to 24·3%. The ability of the cereal plant to compensate for losses may be responsible for this ‘buffering effect’, which apparently is attributable to increased dry-matter production in the presence of large combined pest populations. These results suggest that the existing economic thresholds relating to the effects of cereal aphids and cereal leaf beetle on yields of winter wheat require modification.     

Starch granule size distribution of hard red winter and hard red spring wheat: Its effects on mixing and breadmaking quality

Starch was isolated from 98 hard red winter (HRW) wheat and 99 hard red spring (HRS) wheats. Granule size/volume distributions of the isolated starches were analyzed using a laser diffraction particle size analyzer. There were significant differences in the size distribution between HRW and HRS wheats. The B-granules (<10 μm in diameter) occupied volumes in the range 28.5–49.1% (mean, 39.9%) for HRW wheat, while HRS wheat B-granules occupied volumes in the range 37.1–56.2% (mean, 47.3%). The mean granule sizes of the distribution peaks less than 10 μm in diameter also showed a significant difference (HRW, 4.32 vs. HRS, 4.49 μm), but the mean sizes of the distribution peaks larger than 10 μm were not significantly different (21.54 vs. 21.47 μm). Numerous wheat and flour quality traits also showed significant correlation to starch granule size distributions. Most notably, protein content was inversely correlated with parameters of B-granules. Crumb grain score appeared to be affected by starch granule size distribution, showing significant inverse correlations with B-granules. Furthermore, the linear correlations were improved when the ratio of B-granules to protein content was used, and the polynomial relation was applied. There also appeared to be an optimum range of B-granules for different protein content flour to produce bread with better crumb grain.     

小油菜播种期与密度对黄条跳甲危害程度的影响

在青海西宁地区，小油菜３月２１日～４月２０日播种，密度为４５、７５、１０５、１６５、２２５万株／ｈｍ２。黄条跳甲危害随播期推迟而加重，种植密度大，危害重。危害小油菜的黄条跳甲主要是黄宽条跳甲，其次为黄曲条跳甲，二者比例为３．３∶１。     

Chemical,nutritional and technological characteristics of buck wheat and non-prolamine buckwheat flours in comparison of wheat flour

Chemical, nutritional, and technological characteristics of buckwheat and non-prolamine buckwheat flours in comparison to wheat for celiac patients use have been studied. The results suggested the following conclusions: the 56.5% extraction value for flour obtention is considered good; the buckwheat flour presents methionine and cystine as first limiting amino acids followed by threonine as the second limiting amino acid; the buckwheat flour presents higher content of lysine amino acids than the wheat flour; the buckwheat flour is superior to the wheat flour regarding iron, copper, and magnesium minerals; the buckwheat flour does not present haemagglutinin activity and the tannin content is negligible. Rheological assays indicate that the buckwheat flour does not contain gluten.     

Different effects of earthworms and ants on soil properties of paddy fields in North-East Thailand

As soil engineers, earthworms and ants play major roles in soil functioning, especially in modifying soil physical and chemical properties. This study was conducted in a very constraining environment, i.e., paddy fields which have anoxic conditions (approximately four months per year), and which are affected by soil salinisation during the dry period (approximately eight months per year). This study points out that despite those very adverse conditions, soil invertebrates must be taken into account in the dynamic of soil organic and mineral properties in paddy fields. The effects of one earthworm species, Glyphodrillus sp., and an ant species, Epelysidris sp., on soil physical and chemical properties were determined through elemental soil physical and chemical properties (texture, pH, conductivity, C and N contents) and near infrared reflectance spectroscopy (NIRS) in order to evaluate their ability to influence soil organic matter quality. PCA processed with NIRS data clearly showed that biogenic structures (ant sheetings and earthworm casts) were separated from the control surrounding soil. Earthworms and ants affected differently soil properties. Glyphodrillus sp. increased the SOM content and decreased the pH on the surface of the soil. These effects were attributed to an increase in fine particle content (clay). Conversely, Epelysidris sp. only increased the content of coarse particles (sand) and did not influence either soil pH or SOM content. Soil conductivity was found to be very variable but was not significantly affected by soil invertebrates. These results show the potential of soil macro-fauna to create heterogeneity at small spatial scale and to modify the quality of surface soils even under adverse conditions like saline paddy fields.     

Interacting effects of yak dung deposition and litter quality on litter mass loss and nitrogen dynamics in Tibetan alpine grassland

The effects of grazing‐induced dung deposition on plant growth and soil attributes are well established, but little is known about dung effects on litter decomposition. Here, we tested effects of yak dung on litter decomposition and nutrient content in a Tibetan alpine meadow. We incubated litter of four common alpine meadow species using litter bags in the field. Two low‐quality species (Kobresia capillifolia and Elymus nutans) with low nitrogen (N), high C/N and Lignin/N, and two high‐quality species, (Saussurea nigrescens and Thermopsis lanceolata) were incubated in monoculture with and without dung addition. Mass loss of leaf litter, fibre fraction (cellulose, hemi‐cellulose and lignin), N and phosphorus (P) were measured after 6, 12 and 18 months of incubation in the field. Dung addition significantly increased decomposition constants for low‐quality litter species, but not for high‐quality litter species. Dung addition promoted cellulose and hemi‐cellulose loss, but lignin loss was not affected by dung addition, except after 12 months for high‐quality litter species. Dung reduced N immobilization after 6 months and did not affect subsequent release in low‐quality litter species, and promoted N release after 6 and 12 months in high‐quality litter species. Regardless of litter quality, dung increased P release after 6 and 12 months. Our results suggest grazing‐induced dung deposition may accelerate C and nutrient turnover, primarily through increasing the mass loss of low‐quality litter, P release from litter and N release from high‐quality litter. The mechanisms underlying the effects of dung deposition need to be clarified in future studies.     

Effectiveness of carbofuran applied to the soil and as a seed treatment for the control of aphids on wheat in Northwestern Mexico

The effectiveness of carbofuran 300 ST and 350 L applied to the soil and as a seed treatment was evaluated with two wheat cultivars ‘Genaro’ and ‘Sonoyta’ in the Valle del Yaqui, Ciudad Obregon, Sonora in Northwestern Mexico. Both the soil and seed treatment significantly (P < 0·05) reduced greenbug, Schizaphis graminum (Rondani) and corn leaf aphid, Rhopalosiphum maidis (Fitch) populations. Infestations of greenbugs and corn leaf aphids were 97·8% and 98·3% less, respectively, with the soil application of carbofuran 350 L in the Genaro wheat plots and 91% less for both aphids in the Sonoyta wheat plots than on the untreated controls. Greenbug and corn leaf aphid infestations in the seed treatment with carbofuran 300 ST on the Genaro wheat plots were 93·4% and 52·5% less, respectively, and in the Sonoyta wheat plots, infestations of greenbugs and corn leaf aphids were 92% and 78·9% less, respectively, than on the untreated controls. The wheat plots where carbofuran 350 L was applied to the soil had yields 18% and 16% greater for the Genaro and Sonoyta cultivars, respectively, than the untreated controls, while those plots where carbofuran 300 ST was applied as a seed treatment had yields 15% and 12% greater for the Genaro and Sonoyta cultivars, respectively, than the untreated controls.     

Effects of temperature increase,through spring sowing,on antioxidant power and health-beneficial substances of old and new wheat varieties

The effects of heat stress on the potentially health-beneficial compounds of two old durum wheat genotypes, Timilia and Cappelli and a more recent cultivar, Claudio, were analysed following sowing in winter and in spring. Grain profiling was performed for content of: resistant and not-resistant starch, carotenoids, tripeptide glutathione, GSH and glutathione disulfide, GSSG. Hydrophilic and lipophilic grain extracts were analysed for polyphenol content and antioxidant capacity using two in-vitro assays: 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical quenching and Fremy's salt radical quenching. The antioxidant activities of hydrophilic and lipophilic extracts determined by the two tests were not related. ANOVA and multivariate discriminant analyses showed that genotypic effects had the most significant role in the determination of grain quality. Spring sowing increased the lipophilic/hydrophilic polyphenol ratio, across all of the genotypes. It also enhanced the content of resistant starch (+68%) for Claudio and GSH (+14%) for Timilia. In contrast, if sown in winter rather than spring, Cappelli accumulated more carotenoids (+8.6%) and Timilia accumulated more resistant starch (+81%). Spring sowing had a detrimental effect on yield, but a positive effect on 1000 kernel weight. Consequently, it may lead to a net accumulation of healthy substances and not a relative increase due to grain shrivelling.     

Effects of long-term tillage,crop rotation and nitrogen fertilization on bread-making quality of hard red spring wheat

The effect of tillage system, crop rotation and nitrogen (N) fertilization rates on the quality of hard red spring wheat (Triticum aestivum L.) was studied over a 6-year period under rainfed Mediterranean conditions. Grain yield, test weight, protein content and alveogram parameters (W: alveogram index; P: dough tenacity; L: dough extensibility; P/L: tenacity–extensibility ratio; G: swelling index) were analyzed. Tillage treatments included no tillage (NT) and conventional tillage (CT). Crop rotations were wheat–sunflower (Helianthus annuus L.) (WS), wheat–chickpea (Cicer arietinum L.) (WCP), wheat–faba bean (Vicia faba L.) (WFB), wheat–fallow (WF) and continuous wheat (CW). Nitrogen fertilizer rates were 50, 100 and 150 kg N ha⁻¹ on a Vertisol (Typic Haploxerert). A split–split plot design with four replications was used. Weather conditions over the study years strongly influenced wheat yield and quality. Test weights rose considerably with yield and increased rainfall during the filling period, and fell slightly as N rates increased. Grain protein content increased with rainfall in the month of May (when grain protein accumulation occurs) up to a maximum of 80 mm. Grain protein content peaked at average mean temperatures of around 26–27°C. Protein content and alveogram parameter also improved under CT, following a prior legume crop and with rising N fertilizer rates. Alveogram parameters rose with protein content, although the P/L ratio showed greater imbalance. N fertilizer proved to be a key factor in determining bread-making quality, and the best strategy available to the farmer for optimizing wheat quality. However, the influence of weather conditions and soil residual N should be borne in mind when deciding on the additional fertilizer N to be used as a top dressing with a view to increasing yield and, particularly, enhancing wheat protein content and bread-making quality.     

Effect of drought and elevated temperature on grain zinc and iron concentrations in CIMMYT spring wheat

Abiotic stress caused by increasing temperature and drought is a major limiting factor for wheat productivity around the world. Wheat plays an important role in feeding the world, but climate change threatens its future harvest and nutritional quality. In this study, grain iron (Fe) and zinc (Zn) concentrations of 54 wheat varieties, including CIMMYT derived historic and modern wheat varieties grown in six different environmental conditions, were analyzed. The objective of the study was to evaluate the effect of water and heat stress on the nutritional value of wheat grains with a main emphasis on grain protein content, Zn and Fe concentrations. Significant effects of environment on protein content and grain micronutrients concentration were observed. The protein and Zn concentrations increased in the water and heat stressed environments, whereas Zn and Fe yield per unit area was higher in non-stress conditions. The results suggest that genetic gains in the yield potential of CIMMYT derived wheat varieties have tended to reduce grain Zn, in some instances; however, environmental variability might influence the extent to which this effect manifests itself.     

三种油料作物生产的全要素生产率估计、分解与行业比较 ——基于随机前沿生产函数的分析框架

利用《全国农产品成本收益资料汇编》和随机前沿生产函数方法，对1978-2005年中国三种主要油料作物的全要素生产率增长进行估计和分解，试图寻找其全要素生产率增长的源泉，并重点比较了三大油料作物在1978-2005年间的全要素生产率增长及其构成的表现。结果认为，实现油料生产由粗放型增长向集约型增长的转变，关键在于扩大全要素生产率对整个产出增长的贡献，具体实现路径在于同时实现前沿技术进步和技术效率增进，从而实现全要素生产率的增长。此外，提出了一系列政策建议，希冀能够对促进中国油菜作物的可持续增长有所裨益。     

Effects of enhanced ultraviolet-B radiation on crop structure,growth and yield components of spring wheat under field conditions

Spring wheat (Triticum aestivum) was grown in the field for two consecutive seasons under ambient and supplemental levels of ultraviolet-B (UV-B, 280–315 nm) radiation to determine the potential for alterations in community structure, developmental stages, growth and yield components. The supplemental UV-B radiation simulated depletions of 12, 20, or 25% stratospheric ozone. Spring wheat is a potentially UV-B sensitive species, showing the greatest sensitivity to UV-B radiation at 5.31 kJ m⁻². Delays in development and decrease in plant height were observed at early tillering stage under UV-B treatment, and slowly exacerbated during further development. UV-B radiation changed crop structure, by decreasing the total number of tillers produced and increasing dead shoot number, resulted in fewer head-bearing shoots at ripening stage, and decreased biomass and yield. UV-B radiation decreased the area of the last leaf and leaf area index, but increased specific leaf weight. UV-B radiation inhibited biomass accumulation and altered the patterns of biomass partitioning; these effects might be correlated with yield. Decreases in yield were the result of significant reductions in spike number, grain number per spike and thousand grain weight under UV-B. Generally, the effects of UV-B radiation on developmental stages and crop structure were the most important, they might change the other characteristics of spring wheat crop. The responses of spring wheat crop to enhanced UV-B radiation were assessed, decreases in some crop characteristics caused by a 10 or 20% global ozone depletion were predicted. Ozone depletion had the greatest decrease in yield and the least reduction in plant height.     

N- and S-fertiliser effects on grain composition,industrial quality and end-use in durum wheat

Grain composition, industrial and end-use qualities were analysed in four cultivars of durum wheat subjected to four different nitrogen (N) and sulphur (S) fertiliser treatments in field trials conducted in two successive years in soils not deficient in S:N1S1 (both N and S applied), N1S0 (N application only), N0S1 (S application only) and N0S0 (no fertiliser application). Characters analysed were grain protein content (%P), grain sulphur content (%S), SDS-sedimentation (SDSS), Farinograph energy level (EL), Farinograph tolerance (TOL) and viscoelasticity of cooked pasta (VISCO). Important differences were found between the results from the 2 years, where all parameters showed superior performance in the year of lower rainfall and higher mean temperatures in the final phase of the crop cycle. Significant differences were observed between fertilisers and between cultivars for all parameters. In spite of the non-limiting conditions for S-availability, S-fertiliser application caused significant differences in grain %P, SDSS and N:S ratio, although it did not generate changes in rheological parameters and end-use; these latter parameters were only influenced by N-fertiliser application. For SDSS, the fertiliser treatment N1S1 was generally the best treatment. SDSS was, in general, strongly correlated with the rheological parameter EL and the end-use parameter VISCO, verifying the potential utility of this small-scale test in early generation selection during breeding. However, one cultivar, Chagual, with a very distinct glutenin and gliadin allelic composition compared to the other three cultivars, showed markedly inferior performance for SDSS and EL, yet acceptable performance for VISCO. Given that previous studies have shown that this cultivar shows superior grain yield compared to the other three cultivars, this sounds a cautionary note for the use of SDSS in breeding: selection based upon SDSS performance would have meant this valuable line would have been eliminated from consideration early in the breeding programme.     

Effect of water deficits on within-plot variability in growth and grain yield of spring wheat in northwest China

For adapted cultivars under normal crop densities, biological yield is largely determined by the pool of available resources, e.g. water, nutrients and photosynthetically active radiation, while the nature and intensity of intraspecific competition plays an important role in determining the magnitude of harvest index (HI). Water deficits can drastically reduce the HI from its genetic potential to zero. This study was conducted to determine the effect of drought-weighted intraspecific competition on the HI and, consequently, the grain yield in spring wheat populations along a natural moisture gradient in northwestern China. Along the natural moisture gradient (annual mean rainfall decreased 328→204→185 mm per year, supplemented with 70 mm of irrigation), culm size inequality (as measured by the Gini coefficient of above-ground biomass per culm) always increased, and Lorenz curves were more concave. HI decreased significantly in 1999 (0.364→0.345→0.307) and 2000 (0.341→0.303→0.251). There was a significant negative correlation between the Gini coefficient and the HI of spring wheat along the moisture gradient (R²=0.92, P<0.01). These results suggested that size hierarchies in spring wheat populations are closely correlated with the water regime in the field, and that under greater drought stress there are relatively more smaller plants with lower HI (size-dependent reproductive allocation). Size inequality is an index of competitive status in plant populations under stress environments. Agriculturally, greater size inequality may result in a competitive cost for energy and photosynthetic products, in other words, growth redundancy, which is detrimental to reproductive allocation and consequently, grain yield. The results support the view that stand uniformity in field crops is an important mechanism for increasing grain yield.     

粮油制品中黄曲霉毒素脱毒研究进展

黄曲霉毒素(Aflatoxin,AFT)是一类致癌性极强的剧毒物质,常存在于发霉的粮油制品中。本文综述了黄曲霉毒素去毒方法研究进展,并结合近年来黄曲霉毒素检测技术的研究,提出了将新型纳米材料吸附法与化学方法相结合的脱毒、去毒方法。以期对我国开展粮油黄曲霉毒素脱毒技术体系研究提供一些参考。