Influence of ground cover and herbicide treatments onTetranychus urticae populations in peach orchards

Two-spotted spider mites,Tetranychus urticae Koch, were sampled in peach orchards to quantify abundance in trees over different types of ground cover to document the dispersal of mites from orchard-floor plants to trees. Mite populations developed more quickly and with higher densities in trees over ground cover compared to bare ground, and specifically over covers of predominantly narrowleaf vetch,Vicia angustifolia Reichard. Orchard floor plants such asVicia, Geranium, Lamium, andLepidium contained relatively high densities of mites during early spring, and may have formed the source for later peach-tree infestation.Paper no. 11982 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7643, U.S.A.     

Effect of an invasive ground cover plant on the abundance and diversity of a forest floor spider assemblage

Ground dwelling spiders are important predators in the detrital food web, which plays important roles in nutrient cycling and energy flow in forest ecosystems. The cursorial spider assemblage in a Beech-Maple forest in southwestern Michigan at sites where and invasive plant, Vinca minor, has invaded was compared to a native site within the same forest and to the forest prior to invasion by the plant. Pitfall traps were used to sample cursorial spiders over the course of a summer. Vinca minor substantially altered the forest floor spider assemblage. The invasive plant reduced the total activity-abundance of spiders by nearly 49% and depressed species diversity and evenness; in contrast, species richness was not affected. We found that V. minor changed the guild and family structure with wolf spiders being common at sites where the plant had invaded. Vinca minor reduced the abundance of vagrant web building and crab spiders. Similarity indices revealed that the spider communities between the two sites were quite dissimilar (Bray-Curtis = 0.506; Jaccard’s = 0.520). Importantly, comparison to a study conducted in the same forest 28 years earlier showed that the cursorial spider assemblage in the forest prior to Vinca invasion was very different than it was after Vinca invaded but was similar to the current native site in species and guild composition. We conclude that invasion by Vinca has caused the striking changes we observed in community organization of this important group of forest floor predators. We suggest that changes in the physical structure of the litter/soil microhabitat with the invasion of V. minor are likely the cause of the substantial impacts of the plant on the spider assemblage.     

Weed control and cover crop management affect mycorrhizal colonization of grapevine roots and arbuscular mycorrhizal fungal spore populations in a California vineyard

Arbuscular mycorrhizal (AM) fungi naturally colonize grapevines in California vineyards. Weed control and cover cropping may affect AM fungi directly, through destruction of extraradical hyphae by soil disruption, or indirectly, through effects on populations of mycorrhizal weeds and cover crops. We examined the effects of weed control (cultivation, post-emergence herbicides, pre-emergence herbicides) and cover crops (Secale cereale cv. Merced rye, × Triticosecale cv.Trios 102) on AM fungi in a Central Coast vineyard. Seasonal changes in grapevine mycorrhizal colonization differed among weed control treatments, but did not correspond with seasonal changes in total weed frequency. Differences in grapevine colonization among weed control treatments may be due to differences in mycorrhizal status and/or AM fungal species composition among dominant weed species. Cover crops had no effect on grapevine mycorrhizal colonization, despite higher spring spore populations in cover cropped middles compared to bare middles. Cover crops were mycorrhizal and shared four AM fungal species (Glomus aggregatum, G. etunicatum, G. mosseae, G. scintillans) in common with grapevines. Lack of contact between grapevine roots and cover crop roots may have prevented grapevines from accessing higher spore populations in the middles.     

Influence of grape treatment on the wine yeast populations isolated from spontaneous fermentations

AIM: To study the influence of different methods of grape treatment in wineries on the diversity of the yeast species in spontaneous fermentations. METHODS AND RESULTS: Grapes were crushed and pressed in three different ways followed by spontaneous fermentation. The same grape material picked and crushed aseptically directly in the vineyard served as control. Yeasts isolated at different stages of the fermentation were characterized by 5.8S-ITS-RFLP. Yeasts of the Saccharomyces sensu stricto complex were additionally analysed by microsatellite polymerase chain reaction fingerprinting. The diversity of yeast species isolated from winery fermentations was much greater than from the vineyard fermentation in respect to yeasts of the genus Saccharomyces as well as non-Saccharomyces. CONCLUSIONS: Oenonogical methods alter significantly the yeast diversity in spontaneous fermentations of grape juice. SIGNIFICANCE AND IMPACT OF THE STUDY: Managing spontaneous fermentations successfully depends not only on choosing the suitable grapes but also on the crushing and pressing techniques leading to different yeast populations.     

Yeast populations residing on healthy or botrytis-infected grapes from a vineyard in Attica, Greece

The yeast flora associated with healthy and Botrytis-infected grapes was assessed. Molecular identification methods assigned isolates to six genera and nine species. For the first time Hanseniaspora opuntiae was encountered as an inhabitant of the grape ecosystem. By using DraI, an informative restriction fragment length polymorphism pattern was generated to distinguish H. opuntiae from the closely related organism Hanseniaspora guilliermondii. Botrytis infection resulted in a larger population and greater diversity of yeasts enriched with fermentative or spoilage species.     

施用钾肥对烟粉虱实验种群生命表参数的影响

设置0,30,60,120和240mg/L5种钾肥浓度处理黄瓜植株,测定不同处理黄瓜叶片的含钾量及相应处理上烟粉虱Bemisiatabaci(Gennadius)种群的生命表参数。结果表明,黄瓜叶片含钾量不随钾肥施用量增加而增大,30mg/L钾肥溶液处理的黄瓜叶片含钾量最高。在上述5种钾浓度处理黄瓜植株上,烟粉虱种群的内禀增长率rm分别为0.14,0.17,0.17,0.15和0.13,净增殖率R0依次为47.79,111.55,115.18,61.96和49.58。因此,黄瓜叶片中含钾量高有利于烟粉虱的种群增长。讨论研究结果对生产上烟粉虱种群调控的意义。     

The effect of cover plants management on soil invertebrate fauna in vineyard in Northern Italy

Cover crops are largely used in vineyard management to improve ecological services such as pest and weed control, soil protection from erosion and soil water balance. Few data are available about the effects of cover crops on soil fauna and, in particular, on important generalist predators such as Carabidae and Araneae. We compare the effects of five different cover crops treatments: Sweet Alyssum, Phacelia, Buckwheat, Faba bean and a mixture of Vetch and Oat. A three years experimental trial was developed in Northern Italy. Soil fauna was investigated using pitfall traps. Cover crops seriously affected soil fauna of most taxa. Higher abundance of predators, in particular Carabidae and Staphylinidae, was present in treatments with legumes (Faba bean and Vetch and Oat) while soil Araneae seemed not to be affected. No vineyard pests seemed to be positively affected by cover crops. We confirm the importance of cover crops in increasing soil predator abundance and consequently improving pest control.     

Characterization of Saccharomyces cerevisiae strains isolated from must of grape grown in experimental vineyard

AIMS: Isolation and characterization of indigenous Saccharomyces cerevisiae strains from 12 grape varieties grown in an experimental vineyard of Apulia. METHODS AND RESULTS: Thirty to 40 colonies from each of the 12 fermentations were obtained at the end stage of spontaneous fermentation. By using morphological and physiological methods and by the PCR analysis of internal transcribed ITS1-5,8S-ITS2, the isolates belonging to Saccharomyces genus were identified. These isolates were further characterized by amplification with S. cerevisiae species- and delta element-specific primers, thus allowing the identification of S. cerevisiae strains selected from each of the 12 fermentations. By means of RFLP analysis of mtDNA, each S. cerevisiae population isolated from a single fermentation appeared to constitute a genetically homogenous group. The comparison of the 12 cultivar-specific mtDNA RFLP patterns, allowed classifying the 12 S. cerevisiae populations into three genetically homogenous groups. The isolated strains fermented vigorously in synthetic and grape juice medium and showed high alcohol and sulphur dioxide (SO(2)) resistance and low hydrogen sulphite (H(2)S) production. CONCLUSIONS: The molecular analysis, in conjunction with the traditional morphological and physiological methods, was useful in discriminating at strain level the indigenous population of S. cerevisiae present in a vineyard of Apulia. The dominant S. cerevisiae strains identified in the 12 fermented musts showed potentially important oenological characteristics. SIGNIFICANCE AND IMPACT OF THE STUDY: The characterization of natural S. cerevisiae strains from several typical Italian grapes grown in a restricted experimental vineyard is an important step towards the preservation and exploitation of yeast biodiversity of Apulia, a relevant wine-producing region. The close relationship between the S. cerevisiae strains from different grapes grown in the same vineyard indicated that the occurrence of native strains is representative of the area rather than of the variety of grapes.     

Marker assisted selection for seedlessness in table grape breeding

Seedlessness is one of the most appreciated traits in the table grape (Vitis vinifera L.). The development of new seedless varieties is expensive and time consuming, involving the generation and selection of thousands of hybrids each year. In seeded × seedless crosses, seedlessness commonly segregates 1:1, so molecular markers allowing for the early identification of plants that will produce seedless berries are very useful. This early selection can lead to savings in maintenance and evaluation costs, and allows additional space for larger effective progenies. The variety Sultanina has been the main source of stenospermocarpic seedlessness in table grape breeding. In a previous work, we showed a 198-bp allele at the VMC7F2 microsatellite locus as a potential marker for selection of seedless genotypes due to its close linkage to the major effect seedless QTL, SDI. In this study, we show that stenospermocarpic bred cultivars share a main haplotype around this locus not found in seeded cultivars, which facilitating the development and use of marker assisted selection (MAS) strategies for the selection of seedless plants. In this way, VMC7F2 on its own can be a very useful marker for selecting seedless individuals from segregating crosses. A MAS program based on the presence of the 198-bp allele at VMC7F2 allows the reduction of the progeny size to 54%, selecting most of the seedless individuals. In addition, our results show the existence of other possible sources of stenospermocarpic seedlessness that could provide alternative sources of genetic variation for breeding of this trait.     

长春市园林地被植物研究

通过对长春市园林地被植物的初步调查研究,报道了长春市常见园林地被植物有95种,隶属76属37科。介绍这些地被植物的园林应用及生态习性,指出了长春市园林地被植物绿化中存在的问题,提出了发展长春市园林地被植物的建议。     

Biology and fertility life table of Bactrocera carambolae on grape and acerola

Bactrocera carambolae Drew & Hancock (Diptera: Tephritidae), native of Southeast Asia, is present in Brazil but restricted to Amapá, Pará and Roraima, where it has quarantine pest status. The possible dispersion to other fruit producing regions of Brazil could cause damages, including for exportation, due to quarantine restrictions imposed by fruit importing countries. The objective of this work was to describe the biological parameters and calculate the fertility life table of B. carambolae on grape (Vitis vinifera L.) and acerola (Malpighia emarginata DC.). The experiment was conducted in the laboratory under controlled conditions. The mean number of punctures and the mean number of eggs per female on grapes were 1.48 ± 0.05 and 9.87 ± 0.36, respectively. The mean number puparia per fruit was 0.1 ± 0.02 (grape) and 0.5 ± 0.10 (acerola). The pupal viability was 82.4% (grape) and 70.6% (acerola). The mean time ± SE of one generation, in days, was 25.8 ± 1.10 (grape) and 19.7 ± 0.21 (acerola). The mean fecundity was 1663.8 ± 501.01 (grape) and 206.9 ± 26.21 (acerola) with eggs viability of 5.6% (grape) and 12.5% (acerola). The mean longevity, in days, was 77.3 ± 12.13 on grape and 82.4 ± 4.24 on acerola. The study found that B. carambolae completes its biological cycle on grape and on acerola leaving offspring.     

No variation for Wolbachia-induced hybrid breakdown in two populations of a spider mite

Wolbachia are cytoplasmically transmitted bacteria that infect several species of mites. In the two-spotted spider mite Tetranychus urticae Koch this symbiont can induce reproductive incompatibility. Wolbachia-induced reproductive incompatibility is observed in crosses between Wolbachia-infected (W) males and uninfected (U) females. This incompatibility is expressed in F1 broods as male-biased sex ratios, an effect called cytoplasmic incompatibility (CI). However, in the two-spotted spider mite, Wolbachia-induced reproductive incompatibility may extend to the F2: broods of virgin F1 females from U×W crosses sometimes suffer increased mortality rates. This F2 effect is called hybrid breakdown (HB). Several isofemale lines derived from mites collected from rose and cucumber plants had been previously tested for CI. Here we report on the results obtained for HB.     

Effect of different ground cover management on spider mites (Acari: Tetranychidae) and their phytoseiid (Acari: Phytoseiidae) enemies in citrus orchards

We determined the effect of ground cover on phytoseiid predatory mite populations and the potential biological control of Panonychus citri (McGregor). Results showed that citrus trees with ground cover contained higher population densities of predatory mites and provided better regulation of P. citri than trees in bare soil. The ground cover Ageratum conyzoides L. performed better than Palspalum notatum Flugge in sheltering phytoseiid mites.     

Genetically-based variation between two spider populations in foraging behavior

Summary Optimal foraging theory is based on the assumption that at least some aspects of foraging behavior are genetically determined (Pyke et al. 1977; Kamil and Sargent 1980; Pyke 1984). Nonetheless, very few studies have examined the role of genetics in foraging behavior. Here, we report on geographical differences in the foraging behavior of a spider (Agelenopsis aperta) and investigate whether these differences are genetically determined. Field studies were conducted on two different populations of A. aperta: one residing in a desert riparian habitat, and the other in a desert grassland habitat. Data from the spiders' natural encounters with prey demonstrated that grassland spiders exhibited a higher frequency of attack than riparian spiders towards 13 of 15 prey types, including crickets and ants. Grassland spiders also had shorter latencies to attack 12 of 15 prey types, including crickets and ants, than riparian spiders. Subsequently, we reared grassland and riparian spiders under controlled conditions in the laboratory and observed their interactions with prey to determine whether the populational differences we found in the field could be genetic. Again, grassland spiders showed a shorter latency to attack prey (crickets, ants) than riparian spiders. These latencies were not significantly affected by the hunger state or age of the spiders. Finally, we reared a second generation (F2) of grassland and riparian spiders in the laboratory and observed their interactions with prey to determine whether the populational differences in the previous generation were due to genetic effects or maternal effects. As before, grassland spiders exhibited a shorter latency to attack prey (crickets) than riparian spiders. We conclude that the foraging differences we observed between these two populations of A. aperta are genetically determined. These differences probably have resulted from either natural selection acting directly on attack frequency and the latency to attack prey, or natural selection acting on traits which are genetically correlated with these aspects of foraging behavior.     

Variation in life-history characteristics over a clinal gradient in three populations of a communal orb-weaving spider

Summary Adult size and fecundity, total reproductive biomass, egg size, and spiderling size and resistance to desiccation were compared in three populations of the communal orb-weaving spider,Metepeira spinipes, in Mexico. In a desert population and in one from a moist tropical forest adult size, fecundity, and total reproductive biomass were similar, but were markedly smaller than in a climatologically intermediate agricultural habitat. Egg size and protein content were greater in the desert and agricultural habitats than in the moist forest, but spiderling size increased from desert to agricultural to moist forest populations. Desert spiderlings survived significantly longer than moist forest spiderlings at all humidity treatments over a 10% to 100% range. An explanation for these results is proposed based on apparent differences in energy allocation and expenditure which arise from the distinct climate, colony structure, and prey and space availability in the three habitats.     

Genetic affinities between spider mite Tetranychus urticae populations in a non-agricultural area II

Partial reproductive incompatability between spider mite populations inhabiting adjacent glasshouses is known to be very common. It was found in this study that the size of an area occupied by an intra-fertile population in a non-agricultural habitat is probably in the order of 5–10 km across. Clinal variation in fertility factors is indicated but many irregularities occur.

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Zusammenfassung Partielle Fortpflanzungsunverträglichkeiten zwischen Spinnmilbenpopulationen sind eine sehr verbreitete Erscheinung. In einem Glashauskomplex können Spinnmilben aus benachbarten Glashäusern ausgeprägte Fortpflanzungsbarrieren besitzen, welche sich in hoher Eimortalität bei Kreuzungsweibchen äussern.In nichtlandwirtschaftlichen Situationen ist das Areal einer intrafertilen Population viel grösser (De Boer, 1980). Für die vorliegende Untersuchung wurden die Milben in nichtlandwirtschaftlichen Dünengebieten längs der Nordsee in den Niederlanden, in Belgien und in Nordfrankreich gesammelt. Starke Vermehrungsbarrieren wurden zwischen Populationen entfernter Herkünfte gefunden. Die Grösse des Areals interfertiler Milbenpopulationen misst wahrscheinlich um 5 bis 10 km im Durchmesser. Es gibt Andeutungen für einen allmählichen Übergang der Fruchtbarkeitsfaktoren, doch kommen viele Unregelmässigkeiten vor.