Studies on the feeding of Sitona lineatus L. (Coleoptera: Curculionidae) on white clover (Trifolium repens L.) seedlings

Measurements of feeding damage by sitona weevil (Sitona lineatus L.) adults on differing numbers of seedlings of white clover (Trifolium repens L.) at the first and fourth trifoliate leaf stage were made in the glasshouse at 20°C. S. lineatus consumed more of the trifoliate component of the seedling. Sitona adults caused significant yield reduction at all levels of plant population. Total clover consumption increased with increasing size of sitona population, but consumption per adult weevil was reduced.     

The introduction and recovery in the United States ofAnaphes diana [Hym.: Mymaridae], an egg parasite ofSitona weevils [Col.: Curculionidae]

Anaphes diana (Girault) (=Patasson lameerei Debauche), a mymarid egg parasite ofSitona spp., was introduced from Europe beginning in 1976 and is now tentatively established in the United States. Techniques are described for the separation of eggs ofSitona spp. from soil, using a series of fine-mesh sieves, water, and a saturated salt solution. Data from 9 years of sampling in an alfalfa field at Newark, Del. (>19,300 host eggs extracted), showed that the mean peak density of viable overwintering eggs ofSitona hispidulus (F.) was 14.6 per 100 cm³ of 1 cm deep surface soil. At the study site,Sitona egg densities consistently increased during the fall as a result of oviposition, peaked during January and February and decreased during the spring as a result of egg hatch. Although the incidence of parasitism byA. diana remained surprisingly low (0.29%), the fact that the species was recovered during 3 years and up to 7 years after the last release, indicates that it has colonized at the Delaware release site.      

Effects of intercropping white cabbage with clovers on pest infestation and yield

During two consecutive years the effects of intercropping fresh market white cabbage with two species of clover on pest populations and yield were studied. White cabbage cv. Minicole was intercropped withTrifolium repens (white clover) andTrifolium subterraneum (subterranean clover) as compared to the monocrop. During the season observations were made on pest population developments, especially ofMamestra brassicae L. (cabbage moth),Brevicoryne brassicae L. (cabbage aphid),Delia brassicae L. (cabbage root fly), and evaluation of caterpillar feeding injury. At harvest the yield in quantity and quality was determined to be able to assess the gross financial result. Intercropping effects in terms of suppression of oviposition and larval populations of various pests were found. Although no pesticides were used and competition reduced the weight, the quality of the intercropped cabbages lead to a better financial result compared to the monocropped cabbage crop. The results are discussed in the perspective of the practical implications in the context of IPM.     

Sitona weevils (Coleoptera: Curculionidae) as agents for rapid transfer of nitrogen from white clover (Trifolium repens L.) to perennial ryegrass (Lolium perenne L.)

The effects of root feeding by larvae of Sitona hispidulus (F.) (a common weevil pest of white clover) on the rate of transfer of nitrogen between plants of white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.) were investigated using a nutrient slant board technique. Clover plants, labelled with ¹⁵N were grown adjacent to ryegrass plants and were either infested with Sitona larvae or not infested. Ryegrass plants associated with the infested clover plants had a significantly higher dry matter yield and nitrogen content (75% and 74% respectively) than the uninvested plants, after 33 days exposure to insect herbivory. It was concluded that root feeding insects could play an important role in the cycling of nitrogen in grass/clover swards.     

Glasshouse Experiments on Biocontrol of Cucumber Powdery Mildew (Sphaerotheca fuliginea) by the MycoparasitesVerticillium lecaniiandSporothrix rugulosa

Two potential biological control agents of cucumber powdery mildew (Sphaerotheca fuliginea),Verticillium lecaniiandSporothrix rugulosa,were tested under glasshouse conditions. Two experiments were carried out. In the first experiment, two cucumber varieties with different levels of resistance, cv Corona (susceptible) and cv Flamingo (partially resistant), were used.Verticillium lecaniicontrolled the mildew better thanS. rugulosa.On cv Flamingo,V. lecaniicould keep the mildew severity below 15% infected leaf area for 9 weeks after inoculation withS. fuliginea.Treatment by Hora Oleo 11E, alone or as an additive toV. lecanii,was as good as a fungicide treatment. In the second experiment, weekly and biweekly treatments withV. lecaniiwere compared on cv Flamingo. Weekly treatments withV. lecaniikept mildew severity at a level below 20% infected leaf area during 10 weeks after inoculation withS. fuliginea.If applied to a partially resistant cucumber cultivar,V. lecaniiis an effective candidate for biological control ofS. fuliginea.     

Interaction between Sitona lepidus and red clover lines selected for formononetin content

Adult clover root weevil Sitona lepidus show a feeding preference for white clover Trifolium repens over red clover Trifolium pratense. The effects on S. lepidus of three red clover T. pratense lines, selected for high, medium, or low levels of the isoflavone formononetin in foliage, were compared in three experiments using white clover as a control. In a no‐choice slant board experiment, weevil larval weights were greater for larvae feeding on white clover roots than those feeding on roots of the red clovers. The effect of larval root herbivory on plant growth was similar for all four clovers. Following root herbivory, a large increase in root and shoot formononetin levels was observed in the high‐formononetin selection of red clover but little change in the low‐formononetin red clover. In a no‐choice experiment with sexually mature female adult weevils feeding on foliage of the four clovers, all the red clovers had increased weevil mortality. Female weevils eating the high‐formononetin red clover laid fewer eggs than weevils eating white clover. The red clover diet caused a large accumulation of abdominal fat and/or oil in the weevils, whereas weevils feeding on white clover did not accumulate fat/oil. When sexually immature adult weevils were given a choice of foliage from all four clovers, white clover was eaten preferentially, and the low‐formononetin red clover was preferred to the high‐formononetin red clover. The results suggest that formononetin and associated metabolites in red clover may act as chemical defences against adult S. lepidus and that distribution in forage legumes can be manipulated by plant breeding to improve root health.     

Varietal differences in uptake of 32P labelled phosphate in clover plus ryegrass swards and monocultures

Lolium perenne cv. S.23, L. multiflorum cv. RvP, and Trifolium repens cvs S.184 and Olwen, were grown in mixed sward and monoculture during 1979. Whereas in mixtures grass roots absorbed more ³²P than clover roots, in monoculture clover generally absorbed more ³²P than grass roots. This showed that grass was a very strong competitor for uptake in mixed swards. Clover and grass monocultures absorbed most ³²P from 10 or 15 cm depth in the soil, while grass in mixtures absorbed most ³²P at 22.5 cm depth. Comparing varieties, in monocultures in June, Olwen was most active in absorbing ³²P at 15 cm. In August, Olwen absorbed more at 15 cm and 22.5 cm than S.184 or the grass varieties. Differences in absorption depth between varieties were less in mixtures than in monocultures. S.23 absorbed more ³²P in the late season than RvP, both in monoculture and in mixtures. Thus Olwen differed from S. 184 in depth and timing of uptake, whilst S.23 differed from RvP in time of uptake. Such varietal differences could be exploited by manipulation of depth and timing of fertiliser application to increase the precision of sward management.     

气候变化条件下苦参在我国潜在分布区的预测分析

为了解气候变化情景下苦参在中国的潜在分布区变化,探讨生物气候因子与苦参适宜分布格局的关系.该文通过收集苦参的地理分布点并结合19项生态因子,运用最大熵模型(MaxEnt)和地理信息系统(ArcGIS)对末次盛冰期、当前气候、未来气候三种气候情景下苦参在我国适生区的分布格局进行模拟,并分析影响苦参生长的主导生态因子.结果...     

Spring dispersal ofSitona lineatus: The use of aggregation pheromone traps for monitoring

The spring dispersal ofSitona lineatus L. (Coleoptera; Curculionidae) was investigated on a Danish farm.S. lineatus dispersed by flight in the early spring on sunny, calm days with temperatures above ca. 15°C. Two thirds of the population ofS. lineatus dispersed from perennial leguminous crops (clover and lucerne) in the first period of flight activity. The next dispersal did not occur until one month later despite several intermediate flight activity periods. The first period of dispersal occurred before the germination of the spring sown summer host crop,Vicia faba L. The field bean crop was infested in three later invasions during a period of more than three weeks. The aggregation pheromone, 4-methyl-3,5-heptanedione, had a significant effect on captures of both males and females in cone traps placed on the ground. There was no effect of the pheromone on captures in yellow sticky traps placed 1.5 m above ground. The pheromone effect is discussed in relation to behavioural observations. Both types of traps may be used in a survey system for monitoring spring dispersal ofS. lineatus and optimal timing of insecticide spraying. However, the pheromone cone traps were highly specific whereas all kinds of flying insects were caught in the yellow sticky traps, thus making the latter traps less suitable for monitoring.     

Nodulation of white clover (Trifolium repens) in the absence ofRhizobium

Summary Spontaneous nodules developed on the roots of white clover (Trifolium repens cv. Ladino) in the absence ofRhizobium. A small subpopulation of uninoculated clover plants (0.2%) exhibited white, single-to-multilobed elongated structures on their root systems when grown without fixed nitrogen. Clonal propagation using aseptic stolons confirmed the genetic stability of the observation. Few if any viable bacteria of unknown origin were recovered from surfacesterilized structures. Nodule contents were incapable of eliciting nodulation. Histological observations showed that these structures possessed all the characteristic features of indeterminate nodules, such as active meristem, cortex, endodermal layer, vascular strands, and a central zone with parenchyma cells. Infection threads, intercellular or intracellular bacteria were absent. Instead, numerous starch grains were observed in the central zone, a feature absent in normal nitrogen-fixing nodules. Our observation broadens the concept of spontaneous nodulation, believed to be restricted to alfalfa (Medicago sativa), to other legumes, and suggests a degree of generality among indeterminately nodulated legumes displaying natural heterozygosity.     

Pea leaf weevil herbivory on pea seedlings: effects on growth response and yield

Field experiments were conducted to determine growth and yield responses ofPisum sativum L. to defoliation by adultSitona lineatus (L.). Seedlings grown under conventional (moldboard plowed) and conservation (chisel plowed) tillage treatments were infested for a 1-week period with 0, 1 and 8 weevils per plant at two times: at 75% field emergence and 1 week later. After the early infestation, defoliation for the control, low and high weevil densities was about 0,15 and 50%, respectively, while defoliation after the late infestation was about 0, 10 and 35%. An undercompensatory growth response was observed in one experiment after seedlings were subjected to moderate levels of early defoliation. Exact compensation was observed in two experiments after early infestations of low and highSitona densities.Sitona defoliation reduced the number of pods per plant and pod length in two experiments. However, seed biomass was never significantly reduced. Averaged over all experiments, reduction in seed biomass due to highSitona densities was 10 and 5% for early and late infestations, respectively. Tillage treatments did not affectPisum compensatory growth response, although yield components were sometimes greater in conservation tillage than in conventional tillage, possibly due to slightly greater soil moisture in the conservation tillage plots.     

Selective inhibitors of germination of legume seeds in activated sludge compost

Water extracts of the compost produced from activated sludge and coffee residue were found to be selectively inhibitory to seed germination of some legumes. Germination rate of white clover (Trifolium repens L.), red clover (Trifolium pratense L.) and alfalfa (Medicago sativa L.) seeds were reduced to 2, 29 and 73% of the control, respectively, by water extracts of the compost (20 g l^–1). However, the extracts did not show any inhibition to seed germination of sorghum (Sorghum bicolor Moench), African millet (Eleusine coracana Gaertn.), and Komatsuna (Brassica rapa L.) at the same concentration. The inhibitors in the compost extracts were separated by ion-exchange chromatography and reverse-phase high performance liquid chromatography (HPLC) and the inhibitory activities of seed germination were tested with white clover seeds. Five inhibitors were isolated and identified as 3,4-dichlorophenylacetic acid (3,4-DCP), 3,4-dichlorobenzoic acid (3,4-DCB), 3,4,5-trichlorophenylacetic acid, 3,4,5-trichlorobenzoic acid and mono-2-ethylhexylphthalate by ¹H-, ¹³C-NMR spectroscopy and mass spectrometry. The inhibitory activities of some authentic chemicals of the inhibitors and the related compounds were compared. The results indicated that the main inhibitor in the compost could be 3,4-DCB, which was contained at the concentration of 6.58 mg kg^–1 compost and showed the strongest inhibitory effect on seed germination of white clover among the tested compounds.     

Feeding styles of five species of bottom-feeding fishes of the high Paraná river

Synopsis In this study the diets of five species of bottom-feeding fishes (Prochilodus lineatus, Steindachnerina insculpta, Loricariichthys platymetopon, Trachydoras paraguayensis and Iheringichthys labrosus) were analyzed. Samples were taken in the High Paraná River basin and its floodplain from August 1987 to July 1988 and in February, August and September 1991. The results demonstrated that P. lineatus and S. insculpta were ileophagous, L. platymetopon was detritivorous and I. labrosus and T. paraguayensis were benthophagous. The feeding activity was higher during the flood period for P. lineatus and in dry season for T. paraguayensis. P. lineatus and S. insculpta fed mainly during the day, while I. labrosus and T. paraguayensis during the day and dusk, respectively.     

The 5S DNA units of bread wheat (Triticum aestivum)

A collection of 44 cloned 5S DNA units fromTriticum aestivum cv. Chinese Spring were grouped into 12 sequence-types based on sequence similarity and the respective consensus sequences were then produced. The relationship between these 12 consensus sequences (T. aestivum S 1-S 8 andT. aestivum L 1-L 4), together with two clones sequenced byGerlach andDyer, and the 5S DNA consensus sequences from diploidTriticum spp. were then determined by numerical methods. Both phenetic and cladistic analyses were carried out. The following wheat 5S DNA sequences were found to group with respective sequences from diploidTriticum spp.:T. aestivum S 4, S 6 withT. tauschii S;T. aestivum S 3 withT. monococcum S andT. monococcum S-Rus 7;T. aestivum L 1 andT. aestivum L-G&D withT. speltoides L;T. aestivum L 2, L 3 withT. tauschii L;T. aestivum L 4 withT. monococcum L andT. monococcum L-Rus 12. The analyses suggested that 5 out of the 65S Dna loci present in wheat were identified at the sequence level. The locus that could not be identified in this analysis was the5S Dna-B 1 locus. A group ofT. aestivum sequences (T. aestivum S 1, S 7, S 8, S-G&D) were found to be distinct from the other 5S DNA sequences in the data base. The existence of the distinct group of 5S DNA sequences suggests that there is a gap in our current understanding of wheat evolution with respect to the5S Dna loci.     

TheCBP2 gene fromSaccharomyces douglasii is a functional homologue of theSaccharomyces cerevisiae gene and is essential for respiratory growth in the presence of a wild-type (intron-containing) mitochondrial genome

InSaccharomyces cerevisiae the only known role of theCBP2 gene is the excision of the fifth intron of the mitochondrialcyt b gene (bI5). We have cloned theCBP2 gene fromSaccharomyces douglasii (a close relative ofS. cerevisiae). A comparison of theS. douglasii andS. cerevisiae sequences shows that there are 14% nucleotide substitutions in the coding region, with transitions being three times more frequent than transversions. At the protein level sequence identity is 87%. We have demonstrated that theS. douglasii CBP2 gene is essential for respiratory growth in the presence of a wild-typeS. douglasii mitochondrial genome, but not in the presence of an intronlessS. cerevisiae mitochondrial genome. Also theS. douglasii andS. cerevisiae CBP2 genes are completely interchangeable, even though the intron bI5 is absent from theS. douglasii mitochondrial genome.     

Parasitism ofLygus lineolaris eggs onCoronilla varia,solanum tuberosum,and three host weeds in southeastern Québec

Parasitism ofLygus lineolaris (Palisot de Beauvois) eggs by three species ofMymaridae, Anaphes iole Girault,Erythmelus miridiphagus Dozier andPolynema pratensiphagum Walley and one species ofScelionidae, Telenomus sp., was investigated at Ste-Anne-de-Bellevue, Québec. The maximum level of field parasitism ofL. lineolaris eggs by individual species was 15.4, 53.8, 70.0 and 16,7%, respectively. Parasitoids were retrieved from eggs ofL. lineolaris inserted in stems and branches ofAmaranthus retroflexus L.,Chenopodium album L.,Coronilla varia L.,Rumex obtusifolius L. andSolanum tuberosum L. Amaranthus retroflexus andS. tuberosum sustained a large population ofL. lineolaris and egg parasitism was high enough to consider it as a potential control factor.      

Differential adaptation to water deprivation in first-instar nymphs of the German cockroach (Blattella germanica) and the brown-banded cockroach (Supella longipalpa)

This study compares the relative abilities of rist-instar nymphs of the german cockroach (Blattella germanica L.) and the brown-banded cockroach (Supella longipalpa F.) to survive prolonged periods of food and/or water deprivation.S. longipalpa nymphs survived significantly longer thanB. germanica nymphs when drinking water was absent, but the advantage ofS. longipalpa overB. germanica disappeared if food was also absent. These results are consistent with the hypothesis thatS. longipalpa is adapted to drier habitats than isB. germanica, and suggest thatS. longipalpa nymphs may be more capable of producing and utilizing extra metabolic water from food thanB. germanica nymphs. Evidence from the literature suggests that this species difference applies mainly to juveniles, since adults ofB. germanica andS. longipalpa do not differ in ability to withstand water deprivation, regardless of food availability.     

Effects of condensed tannins in white clover flowers on their digestion in vitro

Protein in white clover (Trifolium repens L.) is poorly utilised by ruminants because of its extensive degradation to ammonia in the rumen. However, white clover produces condensed tannins (CT) in its flowers, which can reduce rumen proteolysis. Effects of increasing proportions of clover dry matter (DM) as flowers (and therefore floral CT) on soluble protein, ammonia and volatile fatty acid (VFA) concentrations were determined with in vitro incubations. Minced mixtures of 0, 250, 500, 750 and 1000 g/kg of DM as white clover flower (F) with the remainder as white clover leaf, were incubated in vitro and sampled after 0, 2, 4, 8, 12 and 24 h. Treatments contained 0, 13, 26, 39 and 52 g CT/kg DM, respectively. A further treatment with 500 g/kg DM as flower and 500 g/kg DM as leaf had polyethylene glycol added to remove effects of CT. Increasing the proportion of white clover as flowers from 0 to 1000 g/kg DM reduced net conversion of plant N to ammonia N from 290 to 120 mM/M at least partly due to reduced solubility of the protein. Treatments with 750 g/kg DM or more as clover flowers reduced ammonia concentrations to levels likely to limit microbial growth. Total VFA production was not affected by flower content, although the proportion of acetate to propionate increased. The contribution of CT to treatment effects was small compared to effects attributed to difference in chemical composition between flowers and leaves.     

Light induction of the clock-controlled geneccg-1 is not transduced through the circadian clock inNeurospora crassa

Ambient light and the circadian clock have been shown to be capable of acting either independently or in an interrelated fashion to regulate the expression of conidiation in the ascomycete fungusNeurospora crassa. Recently several molecular correlates of the circadian clock have been identified in the form of the morning-specific clock-controlled genesccg-1 andccg-2. In this paper we report studies on the regulation ofccg-1, an abundantly expressed gene displaying complex regulation. Consistent with an emerging consensus for clock-controlled genes and conidiation genes inNeurospora, we report thatccg-1 expression is induced by light, and show that this induction is independent of the direct effects of light on the circadian clock. Although circadian regulation of the gene is lost in strains lacking a functional clock, expression ofccg-1 is still not constitutive, but rather fluctuates in concert with changes in developmental potential seen in such strains. Light induction ofccg-1 requires the products of theNeurospora wc-1 andwc-2 genes, but surprisingly the requirement forwc-2 is suppressed in conditional mutants ofcot-1, a gene that encodes a cAMP-dependent protein kinase. These data provide insight into a complex regulatory web, involving at least circadian clock control, light control, metabolic control, and very probably developmental regulation, that governs the expression ofccg-1.