Field evaluation of insect-resistant transgenic Populus nigra trees

The performance of insect-resistant transgenic poplar trees (Populusnigra) expressing a Cry1Ac gene from Bacillus thuringiensis subsp. Kurstaki HD-1 against poplar defoliators was evaluated in the field at the Manas Forest Station in Xinjiang Uygur Autonomous Region during1994–1997. The results showed that the average percentage of highly damaged leaves on the transgenic trees was 10% while that on the control trees in nearby plantations reached 80–90%. The average number of pupae per m² of soil at 20cm depth in transgenic poplar plantation was 18 which was only 20% of that found in the non-transgenic control field. The number of pupae and the leaf-damage on transgenic trees described above are all far below the threshold set for chemical protection measures. The non-transformed poplar trees grown in the same plantation with the transgenic trees were also protected indicating that cross protection occurred between these two kinds of trees. Insect-resistant transgenic poplar trees have a potential application value in afforestation. This revised version was published online in August 2006 with corrections to the Cover Date.     

大庆园林植物节肢动物群落种类构成的调查分析

为了对大庆地区园林植物害虫进行综合治理。对大庆园林植物节肢动物进行群落多样性调查。结果表明：共发现节肢动物105种分属2纲10目49科,其中植食性节肢动物有6目31科54种,鞘翅目昆虫所占比例最大。天敌类群有6目12科38种,其中鞘翅目、膜翅目、蜘蛛目处于主要地位。中性昆虫有2目7科13种,双翅目所占比例最大。大庆地区园林植物节肢动物群落顶位物种和中位物种的丰盛度均低于基位物种的丰盛度。营养层多样性波动幅度相对较大,种的均匀度变化幅度小。     

Insect communities related to wheat and coriander cropping histories and essential oils in the Rolling Pampa, Argentina

Intensive land use in the Rolling Pampa of Argentina have resulted in a mosaic of fields with different cultural histories creating different soil environments, which interact with crops and cropping activities producing a wide range of habitats for insects. Species and functions in canopy structure, food quality and essential oils of the crop–weed associations may vary depending on the field's cropping history and management (i.e. crops, soil degradation, weeding and fertilization). Species composition and functional structure of insect communities may respond to these changes. We studied insect communities in wheat and coriander crops that differed in their canopy structures, essential oil production, and the cropping histories of the fields on which they grew. For this purpose we planted wheat (Triticum aestivum L.), and two coriander (Coriandrum sativum L.) landraces in plots with two levels of weeding and fertilization. The crops were grown in two consecutive years at two locations differing in cropping history and related to this in level of soil degradation. Insects were sampled in all plots at crop full flowering, and were classified and related to agronomic variables and to essential oils using multivariate techniques. Among all the environmental factors tested in this study, year and soil degradation were the main factors explaining insect community structure; and also weed community structure in unweeded plots. The proportion of essential oil components varied with cropping history, suggesting an association among soil properties indicative of soil degradation, plant chemical signals and insect distribution. Although insect community composition varied widely, functional structure was very similar among crop–weed communities. Soil degradation appeared to have affected directly crop–weed communities and insects’ assemblages, since no consistent relationship was found between plant composition and insect community structure. It can be hypothesized that soil degradation might have affected the amount of volatiles produced especially by coriander, generating a “soil degradation scent” that determined the structure in the insect community, and/or the soil itself emitted different signals, in relation to changes in its physical, chemical and biological characteristics.     

Selection for adaptation in multipurpose trees and shrubs for production and function in agroforestry systems

Summary With the greater uniformity in site conditions in cultivated fields and higher levels of inputs (soil amendments and labour) for modern agroforestry systems, selection and breeding for optimal tree adaptation to site conditions and management practices call for strategies radically different from those for plantation forestry. Furthermore, specific requirements for the most efficient growth resource sharing arrangements between the tree and its companion crop call for evaluation both above-ground and below-ground tree growth characteristics in much greater details than has been the case for forestry practice.Specific adaptations in tree-soil relations are highlighted. Tree ideotype profiles are defined for a valuable fodder species (Calliandra calothyrsus) and a valuable timber species (Grevillea robusta). Results from half-sib progeny testing experiment on C. calothyrsus in alley farming system indicate differential adaptedness to frequent cutting for fodder production among the families after 6 cutting cycles (over a period of 2 years). If this differential response to frequent cutting among genotypes is confirmed, phyllomorphs which are more tolerant to this management practice could be selected for further improvement research.Excavation of 2 trees per family within G. robusta half-sib progeny testing experiments at two locations in Kenya provided the base for studying (a) variations in root growth patterns and (b) correlations between stem and root growth patterns in the background of efficient soil resource sharing strategies and of potentials for indirect selection for root growth characteristics. Analyses based on 7 categories of root growth and 7 categories of stem growth patterns involving 94 families selected in Australia and 60 families selected from landraces in Kenya indicate (a) insignificant variation among families in root growth patterns and (b) non existent or weak correlations between stem and root growth pattenrs.     

Plant–soil interactions in wheat and coriander crops driving arthropod assemblies through volatile compounds

Arthropod assemblies are frequently determined by bottom-up interactions that include emission of organic volatile compounds. Therefore, changes in soil characteristics associated with land use history can influence the volatile emissions of plants affecting the structure of arthropod assemblies in croplands. This study aims (1) to study the relationships between soil degradation levels due to land-use history, and the change in particular soil chemical characteristics; (2) to analyze plant–soil interactions quantifying the effect of soil degradation on the production of biomass and grain yield of coriander and wheat crops, and on the production and chemical composition of volatile secondary metabolites in coriander grain; (3) to find the relationship between the analyzed plant–soil interactions and the emission of volatile signals affecting arthropod assemblies; and (4) to determine the relationship between particular chemical soil characteristics and the structure of arthropod assemblies. For these purpose, two experiments were carried out in which volatile compounds were conducted from source plots with soils with different levels of degradation, sown with wheat or coriander, to sink plots with similar soil, sown with wheat. Crops were evaluated on source plots, and the arthropods communities were assessed on sink-plots. Coriander produced high biomass, grain yield and essential oil in the favorable environments and wheat produced higher biomass and grain yield in soil with low degradation than with high degradation. Particular chemical soil elements, for example, Na, Fe, Mn, N and CEC and essential oil components, for example, γ-trepanned, p-cymene, asinine and β-pinene could be involved in the arthropods assemblies. Based on these results, arthropods communities in agricultural systems are, at least, partially controlled by chemical signals, which depend on plant–soil interactions.     

Performance of <Emphasis Type="Italic">Coffea arabica</Emphasis> F1 hybrids in agroforestry and full-sun cropping systems in comparison with American pure line cultivars

Coffea arabica F1 hybrids derived from crosses between wild Sudan-Ethiopian and American cultivars and propagated by somatic embryogenesis have been obtained in Central America. These new hybrids considerably enhanced the genetic diversity of coffee in the region. We conducted 15 trials to assess whether using hybrids represents substantial genetic progress in terms of productivity in agroforestry and full-sun cropping systems. The new germplasm was grown in the same conditions as the best American cultivar (homozygous pure lines). The results showed that yields of hybrids were earlier and superior to those of American cultivars. The hybrids were also more stable than the American cultivars in all environments. In the agroforestry system, the mean yield of hybrids was 58% higher than that of the American cultivars, while the mean yield of hybrids in the full-sun system was 34% higher. Coffee-based agroforestry systems (AS) are considered effective in protecting the environment in the volcanic cordilleras of Central America. We found that introducing hybrids in coffee-based AS can considerably increase productivity. This finding could be a convincing argument to encourage coffee growers who have adopted the full-sun cropping system to return to agroforestry cropping systems. Finally, the conditions for large-scale dissemination of those new hybrids—which represent a major innovation for C. arabica cropping—was analysed.     

Is somaclonal variation a reliable tool for spring wheat improvement?

Summary Seed progeny of tissue culture regenerants of a spring wheat (Triticum aestivum L. cv. HY320) was evaluated for key agronomic traits for three years under field conditions. Initially, 27 regenerant families were tested in hill plots. Among-family and within-family variation was generally highly significant (p < 0.01) and nonsignificant, respectively. The variation observed among regenerants on the basis of hill plot testing was not duplicated in subsequent four-row plot experiments. On average, regenerant families yielded 28 and 5% less than the control in dryland and irrigated tests, respectively. Low yielding regenerants tended to produce fewer, lighter kernels per spike. Higher grain protein levels among regenerants were associated with low yields (r=0.85). This study demonstrated that putative somaclonal variation arising from tissue culture failed to produce genotypes agronomically superior to the parental cultivar, HY 320.NRCC Publication No. 33533     

Effect of end-border condition on small-plot yield of cucumber

Summary Twelve or 14 cultivars and breeding lines (collectively referred to as lines hereafter) of pickling and fresh-market cucumbers (Cucumis sativus L.) were evaluated in 1.5 m long plots. The plots were harvested once when the check lines reached the 10% oversized fruit stage, and total, marketable, and early (oversized) number of fruits per plot was counted. The plots were planted with or without 1.5 m long end-borders to determine whether end-borders can be eliminated in small-plot trials where seed numbers and field space are limiting. Yield in unbordered plots was inflated 5 to 21% over bordered plots, but there was generally no significant effect in the analysis of variance for line x end-border condition. Therefore, end-borders are not needed when comparing different lines.     

洞庭湖区播种期、耕作方式和施肥对大麦农艺性状的影响

为了推进湖南饲用大麦(Hordeum vulgare L.)的种植,对冬闲稻田进行有效开发,探索环洞庭湖区大麦栽培抗倒高产节本的栽培措施。本研究使用裂裂区设计的田间试验方法调查不同播种期、不同耕作方式和施肥对大麦产量构成因子如有效穗数、穗粒数和千粒重等的影响。结果表明：洞庭湖区冬闲田种植大麦,不同播种期、耕作方式和施肥对大麦的农艺性状和产量有显著的影响(P<0.05)。在不影响双季稻生产的情况下,播种期最好不要超过11月4日,且翻耕可以显著提高大麦产量(P<0.05),而施肥对大麦产量影响较小,可以考虑不施肥。总体来看,‘华大麦4号’的小区种子产量最高达到9.5 kg每小区,适合洞庭湖区种植并可进行进一步栽培研究。     

Impact of the Cropping Systems of a Minor Dry Season on the Growth, Yields and Nitrogen Uptake of Maize (Zea mays L) Grown in the Humid Tropics during the Major Rainy Season

A field study evaluated the residual effect of a cropping system in two minor (dry) seasons on the productivity pattern and nitrogen utilization of a maize crop grown in the subsequent major (wet) seasons. The cropping systems established in the minor seasons, where evaporation exceeds rainfall, were either monocultures of maize (Zea mays L), or maize intercropped with either common bean (Phaseolus vulgaris L) or sunhemp (Crotolaria juncea L). In addition, monocultures of two green manures, namely sunhemp (Crotolaria juncea) or Tithonia (Tithonia diversifolia), were established. The residues of maize and beans and the green manures were incorporated at the end of the minor season; at the onset of rains in the major season, maize crops were established on the same plots. Germination of maize was not affected by the previous cropping system. In contrast, crop growth and yields of maize and nitrogen utilization were affected by the previous cropping system. Optimum growth and highest yields were procured in maize that was grown after a green manure crop. Similarly, although the yields were high, the planting of a green manure crop reduced nitrogen utilization by maize in the major season, thereby indicating its potential contribution to sustainability, due to its lower mining of soil nitrogen. On the basis of the results of this two‐year study, the impact of cropping systems in minor seasons on the productivity of maize, a very important highland cereal in the tropics, grown under rain‐fed conditions in a major season, is presented.     

Competition effects in cocoa (Theobroma cacao L.) hybrid trials

A method developed in coffee tree breeding to assess family competitioneffects (partner effects) in comparative variety trials was applied to thecocoa tree (Theobroma cacao L.). The study was conducted in ahybrid comparative trial planted in French Guiana, involving twelve familiesof 50 trees in a totally randomized single-tree plot design, at a density of1,667 trees per hectare. The trial was thinned at 10 years, at a rate of twoout of four rows. Competition was studied with reference to juvenile andadult vegetative vigour, and to periodic and cumulative yields (number ofpods, potential weight, average weight of one pod, and the production:vigour ratio). At the end of the trial, after thirteen years of monitoring,competition effects were revealed which explained 8 to 10% of theresidual variance after removal of the hybrid and micro-environment effects.These effects, which were detected as early as 18 months, occurred earlierthan generally acknowledged. Under the trial conditions, the families couldbe classed as aggressive, stimulating or passive for their neighbours.Vegetative vigour (trunk cross-section) explained 34% of the competitioneffects (partner effects), which, with hindsight, vindicated the use of theproduction : vigour ratio as the main selection criterion in cocoa breeding.The partner effects noted on the production variables were never explainedby any production variable, hence non-aggressive high-yielding families canbe selected.     

Evaluation of yield stability of cowpea under sole and intercrop management in Nigeria

Summary Nine cowpea (Vigna unguiculata (L.) Walp.) breeding lines were grown in 13 experiments under sole crop and intercrop management, with and without insecticide application, in Nigeria. Cowpea was intercropped with cassava (Manihot esculenta Cranz), maize (Zea mays L.) and maize-cassava in the forest zone and with sorghum (Sorghum bicolor Moench.) and millet (Pennisetum glaucum (L.) R.Br.) in the savanna zone. Line by cropping system interactions were significant in 5 of 13 experiments and line by insecticide treatment interactions were significant in 2 of 13 experiments. Cowpea yield was severely depressed in intercropped plots and in plots to which no insecticide was applied. Among-environment variation in cowpea yield was greater when no insecticide was applied. Within each management treatment, the yield performance and stability of the cowpea lines was examined. Stability was assessed both by examining among-environment coefficients of variation and by regression analysis. Several of the breeding lines evaluated appeared promising under different levels of management and in a diversity of environments.     

Effects of walnut trees on biological nitrogen fixation and yield of intercropped alfalfa in a Mediterranean agroforestry system

While intercropping annual non nitrogen-fixing crops with deciduous hardwood species is now well documented, there is a need to investigate if nitrogen-fixing intercrops may succeed in agroforestry systems. Intercropping with trees usually leads to a decline in crop yield, and could in addition possibly reduce the biological N fixation (BNF) over time due to the competition for resources. In a Mediterranean experimental site, 17 year-old hybrid walnut trees (Juglans nigra x Juglans regia L.) planted in East-West oriented lines were intercropped with alfalfa (Medicago sativa L.) to assess the impact of competition for light and water on alfalfa yield and BNF. Alfalfa yield and shoot δ¹⁵N values (a proxy for the proportion of N derived from the air, %Ndfa) were measured during one year at different distances from the tree row in two directions (north and south). Alfalfa yield was reduced close to the tree row (−28% and −22% on the northern and southern sides respectively), but less than the reduction of irradiation (−59% and −33% respectively). Shading improved by 35% the apparent light use efficiency (LUE: aboveground biomass produced per unit of global radiation) of alfalfa, indicating that alfalfa was shade tolerant at this Mediterranean site. Alfalfa shoot δ¹⁵N values were lower close to the tree rows than at mid inter-row: BNF was stimulated close to the trees. Compensative and facilitative mechanisms between trees and alfalfa plants led to a rise in LUE and%Ndfa in shaded areas. These results contradict the frequent assumption that N fixation is reduced in the shade of trees. Appropriate tree canopy management may help maintain light competition between trees and alfalfa to a level that still enhance complementary, which would further improve the sustainability of the use of alfalfa as an intercrop in Mediterranean regions.     

有机管理对茶园节肢动物群落稳定性的影响

通过对不同管理的有机茶园和常规茶园益、害节肢动物群落的调查，并根据群落指标：丰富度、均匀度、多样性指数、优势度分析群落的稳定性。研究结果表明，有机管理的茶园群落稳定性大于对照茶园。根据最远距离法进行聚类分析，有机管理茶园和常规管理茶园分属不同的类群，说明有机管理方式有利于茶园节肢动物群落的稳定。     

林分密度对华北落叶松人工林林下植被多样性影响的研究

以河北省塞罕坝机械林场为研究地点,采用标准地调查法,研究在立地条件一致的情况下林分密度对华北落叶松人工林林下植被多样性的影响,结果表明：在华北落叶松人工林林下植被各多样性指数中,灌木的Simpson指数D和草本植物的Shannon-Wiener指数H受林分密度的影响最大。林分密度对华北落叶松人工林林下植被的科、属组成以及物种丰富度、物种多样性、物种均匀度均有一定程度的影响,随着林分密度的增加它们均呈不同程度降低的趋势。     

Cover crops and interrow tillage for weed control in short season maize (Zea mays)

Weed competition can cause substantial maize (Zea mays L.) yield reductions. Interseeding maize with cover crops or a combination of interrow cultivation and interseeded cover crops are possible alternative methods of weed control. This study was conducted to examine the potential of interrow cultivation plus cover crops to reduce weed density in maize without reducing the grain yield. Field experiments were conducted in 1993 and 1994 at two sites in Québec to determine the effects of planting 12 cover crops with maize on weed control. Fall rye (Secale cereal L.), hairy vetch (Vicia villosa Roth), a mixture of red clover (Trifolium pratense L.) and ryegrass (Lolium multiflorum Lam), a mixture of white clover (Trifolium repens L.) and ryegrass, subterranean clover (Trifolium subterraneum L.), yellow sweet clover (Meliotus officinalis Lam), black medic (Medicago lupulina L.), Persian clover (Trifolium resupinatum L.), strawberry clover (Trifolium fragiferum L.), crimson clover (Trifolium incarnatum L.), alfalfa (Medicago sativa L.), and berseem clover (Trifolium alexandrinum L.) were seeded at two planting dates, 10 and 20 days after maize emergence. Interrow cultivation was carried out weekly until forage seeding, with a final cultivation being conducted just prior to cover crop seeding. Cover crop planting date did not affect maize yields or the ability of interrow tillage plus cover crops to suppress the development of weed populations. Maize yield was less affected by the interseeded cover crops under conditions of adequate rainfall. Corn planted in fields heavily infested with weeds resulted in substantial yield reductions even when rainfall was adequate. Except for 1993 at l'Assomption interrow tillage plus cover crop treatments had consistently lower weed biomass when compared to the weedy control. Most of the weed control was due to the interrow cultivation performed prior to seeding of the cover crops. The lowest weed density occurred in the herbicide treated plots. The ability of interrow tillage plus cover crops to suppress the development of weeds was affected by the level of weed infestation, the growing conditions and location. The cover crops provide additional weed control but the interrrow tillage or some herbicide application may still be necessary.     

Biometrical analysis of alternative plot types for selection in rye

Summary Maximizing the efficiency of selection for yield and baking quality of winter rye (Secale cereale L.) requires reliable knowledge on the pertinent population parameters. This study reports estimates of variances, heritabilities and genetic correlations from a) large (5 m²) drilled (LD) plots, b) micro drilled (MD) plots, and c) one-row plots of 4 spaced plants (SP). Thirty eight single crosses of rye were grown at two locations for two years in LD, MD and SP plots replicated 2, 4, and 6 times, respectively. Genotypic differences were significant in all plot types for all agronomic and quality traits, although estimates of genetic variances were smaller in LD than MD or SP plots for grain yield, 32-spike weight, and kernels per spike. Heritabilities on an entry mean basis (0.62 to 0.95) were similar among plot types, but on a single plot basis estimates were lower for SP than for MD or LD plots. Genetic correlations were high between all three plot types, with correlations between LD and SP plots being approximately 1.0 for falling number, thousand-kernel weight, and bloom date, 0.90 for grain yield, kernels per spike, test weight and height, and 0.70 for tiller number. Based on the high heritabilities achieved in small plots and the close agreement between MD- or SP- with LD-plot performance we conclude that greater use should be made of small plot types when selecting for yield and quality in winter rye.     

Effect of date of sampling and plant density upon size and digestibility of reproductive tillers of Lolium perenne L.

Summary Evaluation of forage germplasm digestibility is an important factor in screening programmes. The major problems involve the relevance of estimations made in spaced plants to plot performance, the effect of maturity, leaf: stem ratio and the choice of plant organ to be analysed. The use of stems of reproductive tiller proved successful in Lolium multiflorum. In the present experiment the effect of dates of sampling (date 1=28/6; date 2=5/7; date 3=12/7/83) and of plant densities (spaced plants and plots) on the digestibility of reproductive tillers of L. perenne cv. Marta 23 days after ear emergence was evaluated. After harvesting, the following characters were recorded on each tiller: tiller length and diameter, and spike and flag leaf length. Leaf blades and sheaths were then removed, the tillers dried and milled individually, and the in vitro digestibility assessed. The data were analysed by Analysis of Variance, Principal Components Analysis and Numerical Classification followed by a study of how the variables contributed to the derived group structure. Results: I-Plots: digestibility values were 63.4, 60.3 and 56.6% (P<0.01), respectively, for the sampling dates 1, 2 and 3. The Cramer Value (0.41) shows some correlation between tiller size and digestibility. Tillers from date 3 tend to be smaller than the others but the separation is not very clear. II-Spaced plants: digestibility values were 63.2, 60.0 and 60.8%, respectively, for dates 1, 2 and 3. Analysis of variance showed differences (P<0.01) between dates and also between genotypes. The Cramer Value (0.23) shows less correlation between tiller size and digestibility: however, tillers from dates 1 and 3 are clearly separated on the basis of size. Tillers from date 3 being smaller, date 2 tillers are located in between those from dates 1 and 3. III-Plots and single plants combined: Tillers from plots are larger than tillers from spaced plants in sampling dates 2 and 3. The Cramer Value for digestibility (0.14) is the lowest one. The results indicate differences in size and digestibility of reproductive tillers of L. perenne when contrasting situations are being compared, which suggest influence of environmental conditions upon the characters evaluated in the experiment. The differences are sufficiently high so that the use of this technique, when populations of L. perenne with wide variation in flowering dates are being evaluated, is not recommended.     

Stable resistance against the leaf miner <Emphasis Type="Italic">Leucoptera coffeella</Emphasis> expressed by genetically transformed <Emphasis Type="Italic">Coffea canephora</Emphasis> in a pluriannual field experiment in French Guiana

Summary A pluriannual field trial of transgenic clones of Coffea canephora (the Robusta coffee tree) transformed for resistance to the lepidopteran coffee leaf miner Leucoptera coffeella was installed in French Guiana. Fifty-eight transformed clones produced by transformation of the C. canephora clone 126 were planted. They were harbouring the pEF1α constitutive promoter of Arabidopsis thaliana controlling either the Bacillus thuringiensis native gene for the cry1Ac insecticidal protein (eight clones) or a synthetic cry1Ac gene (53 clones). The vectors for the transformation were a strain of the bacterium Agrobacterium tumefaciens and one of Agrobacterium rhizogenes. The transformed clones were generally independent, presenting different integration patterns of the genetic construct. Four randomly distributed groups of five plants per transformed clone were planted along with 60 untransformed control trees. Over a 4-year period after plantation six releases of L. coffeella were performed. Mines on the leaves are the marks of larvae development and were counted on plants. A majority of the independent transformed clones harbouring the synthetic gene and transformed by the strain of A. tumefaciens displayed constantly much less mines than the control, therefore expressing a stable resistance. The need for complementary research is presented.