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Ambrosia trifida L. is native to North America, has been introduced into many countries in Europe and East Asia, and is also expanding its habitat in its native ranges. Ambrosia trifida grows in sunny and humid environments, such as grasslands, riverbanks, floodplains, abandoned places, and agricultural fields, as an invasive plant species. Ambrosia trifida has a strong adaptive ability to adverse conditions and shows great variation in seed germination phenology and plant morphology in response to environmental conditions. Effective natural enemies have not been found in its native or introduced ranges. The species is allelopathic and contains several allelochemicals. These characteristics may contribute to the competitive ability and invasiveness of this species. Ambrosia trifida significantly reduces species diversity and plant abundance in its infested plant communities. The species also causes significant yield loss in summer crop production, such as in maize, soybean, sunflower, and cotton production. Ambrosia trifida is capable of rapid evolution against herbicide pressure. Populations of Ambrosia trifida resistant to glyphosate, ALS-inhibiting herbicides, and PPO-inhibiting herbicides, as well as cross-resistant populations, have already appeared. An integrated weed management protocol with a more diverse combination of herbicide sites of action and other practices, such as tillage, the use of different crop species, crop rotation, smart decision tools, and innovative equipment, would be essential to mitigate herbicide-dependent weed control practices and may be one sustainable system for Ambrosia trifida management. [ABSTRACT FROM AUTHOR]

Robinia pseudoacacia is native to North America and has been introduced into many other countries in Europe, South and South East Asia, South America, Africa, and Oceania. The species has been planted intensively in a large area of these countries because of its ornamental and economic values. However, R. pseudoacacia often infests unintended places, including protected areas, and causes significant ecological impacts. The species is now listed as one of the harmful invasive plant species. The characteristics of its life-history, such as the high growth and reproduction rate and adaptive ability to various environmental conditions, may contribute to the invasiveness of the species. The defense ability against natural enemies such as pathogenic fungi and herbivores and its allelopathic potential against the competitive plant species may also contribute to its invasiveness. The R. pseudoacacia infestation alters the ecological functions of the plant community, including the soil microbe community, and reduces the abundance and diversity of the native plant species, including vertebrates and invertebrates in the introduced ranges. R. pseudoacacia is a shade intolerant and early successional tree species and is replaced by larger and more shade tolerant tree species in the native ranges, while plant succession seems not to occur always in the introduced ranges across the different ages of R. pseudoacacia stands. Several other review articles have summarized the afforestation, utilization, biology, and management of the species, but this is the first review focusing on the invasive mechanism of R. pseudoacacia and its impacts on species diversity. [ABSTRACT FROM AUTHOR]

Ageratum conyzoides L. is native to Tropical America, and it has naturalized in many other tropical, subtropical, and temperate countries in South America, Central and Southern Africa, South and East Asia, Eastern Austria, and Europe. The population of the species has increased dramatically as an invasive alien species, and it causes significant problems in agriculture and natural ecosystems. The life history traits of Ageratum conyzoides, such as its short life cycle, early reproductive maturity, prolific seed production, and high adaptive ability to various environmental conditions, may contribute to its naturalization and increasing population. Possible evidence of the molecules involved in the defense of Ageratum conyzoides against its natural enemies, such as herbivore insects and fungal pathogens, and the allelochemicals involved in its competitive ability against neighboring plant species has been accumulated in the literature. The volatiles, essential oils, extracts, residues, and/or rhizosphere soil of Ageratum conyzoides show insecticidal, fungicidal, nematocidal, and allelopathic activity. The pyrrolizidine alkaloids lycopsamine and echinatine, found in the species, are highly toxic and show insecticidal activity. Benzopyran derivatives precocenes I and II show inhibitory activity against insect juvenile hormone biosynthesis and trichothecene mycotoxin biosynthesis. A mixture of volatiles emitted from Ageratum conyzoides, such as β-caryophyllene, β-bisabolene, and β-farnesene, may work as herbivore-induced plant volatiles, which are involved in the indirect defense function against herbivore insects. Flavonoids, such as nobiletin, eupalestin, 5′-methoxynobiletin, 5,6,7,3′,4′,5′-hexamethoxyflavone, and 5,6,8,3,4′,5′-hexamethoxyflavone, show inhibitory activity against the spore germination of pathogenic fungi. The benzoic acid and cinnamic acid derivatives found in the species, such as protocatechuic acid, gallic acid, p-coumaric acid, p-hydroxybenzoic acid, and ferulic acid, may act as allelopathic agents, causing the germination and growth inhibition of competitive plant species. These molecules produced by Ageratum conyzoides may act as defense molecules against its natural enemies and as allelochemicals against neighboring plant species, and they may contribute to the naturalization of the increasing population of Ageratum conyzoides in new habitats as an invasive plant species. This article presents the first review focusing on the defense function and allelopathy of Ageratum conyzoides. [ABSTRACT FROM AUTHOR]

Ludwigia decurrens Walter, belonging to the Onagraceae family, is native to southeastern and southcentral USA and has spread quickly, colonizing wetlands in South and Central America, East and South Asia and Africa. Ludwigia decurrens also infests rice paddy fields and causes serious damage to rice production. The phenomenon of allelopathy is often observed in invasive plant species and contributes to their invasive characteristics. However, no information has been made available on the allelopathy of L. decurrens against wetland species, including Oryza sativa (rice), or on its allelochemicals. Aqueous methanol extracts of whole L. decurrens plants showed allelopathic activity against O. sativa and paddy weeds, Echinochloa crus-galli and Monochoria vaginalis in an extract-concentration-dependent manner. Two allelochemicals, loliolide and dehydrololiolide, were isolated from the L. decurrens extracts through a bioassay-guided separation process using O. sativa as the test plant species. Loliolide and dehydrololiolide also suppressed the growth of O. sativa and E. crus-galli in a concentration-dependent manner. Thus, loliolide and dehydrololiolide may be involved in the allelopathy of L. decurrens and may provide a competitive advantage for L. decurrens due to their growth inhibitory activity. However, the inhibitory activity of loliolide was about 3-fold greater than that of dehydrololiolide. These investigations suggest the allelopathy of L. decurrens may play an important role in the invasion of the species into rice paddy fields and other wetlands. This is the first report on the allelopathy of L. decurrens against wetland species and the isolation and identification of the allelochemicals in L. decurrens. [ABSTRACT FROM AUTHOR]

Second-harmonic generation in a uniaxial crystal in total-reflection geometry is precisely measured. A Y-cut plate and a Z-cut plate of quartz crystals were used as samples. The incident wave is totally reflected by a glass prism in contact with the sample crystal, and an evanescent wave penetrates into the sample as a fundamental wave. The results gave the quantitative values of the components for a nonlinear optical susceptibility tensor with various polarizations and with Y-cut and Z-cut quartz plates. This technique can be applied to various samples to evaluate their nonlinear optical efficiencies.

Abstract Background Peanut (Arachis hypogaea) is an autogamous allotetraploid legume (2n = 4x = 40) that is widely cultivated as a food and oil crop. More than 6,000 DNA markers have been developed in Arachis spp., but high-density linkage maps useful for genetics, genomics, and breeding have not been constructed due to extremely low genetic diversity. Polymorphic marker loci are useful for the construction of such high-density linkage maps. The present study used in silico analysis to develop simple sequence repeat-based and transposon-based markers. Results The use of in silico analysis increased the efficiency of polymorphic marker development by more than 3-fold. In total, 926 (34.2%) of 2,702 markers showed polymorphisms between parental lines of the mapping population. Linkage analysis of the 926 markers along with 253 polymorphic markers selected from 4,449 published markers generated 21 linkage groups covering 2,166.4 cM with 1,114 loci. Based on the map thus produced, 23 quantitative trait loci (QTLs) for 15 agronomical traits were detected. Another linkage map with 326 loci was also constructed and revealed a relationship between the genotypes of the FAD2 genes and the ratio of oleic/linoleic acid in peanut seed. Conclusions In silico analysis of polymorphisms increased the efficiency of polymorphic marker development, and contributed to the construction of high-density linkage maps in cultivated peanut. The resultant maps were applicable to QTL analysis. Marker subsets and linkage maps developed in this study should be useful for genetics, genomics, and breeding in Arachis. The data are available at the Kazusa DNA Marker Database (http://marker.kazusa.or.jp).

The cooling process of DNA gel (20 wt./wt.%–40 wt./wt.%) with various counterions has been investigated by low frequency Raman spectroscopy and differential scanning calorimetry (DSC). We have found that the dynamics of water of hydration is different among counterion species below 0 °C. For K-, Rb-, Sr-, and Ba-DNA gels, a part of nonfreezing water slowly changes its dynamical structure, when the gel is kept at ∼-30 °C after cooling below -50 °C. This relaxation process can be monitored both by the frequency increment of the lowest Raman band from ∼17 to ∼20 cm-1 and by the intensity increment of an extra endothermic peak in DSC heating curves. We propose that this relaxation process corresponds to the crystallization of a part of nonfreezing water and is caused by the rearrangement of the secondary hydrated water including counterions when the temperature is held at ∼-30 °C. This relaxation process cannot be observed for NH4- and Li-DNA gels. For Na-, Mg-, and Ca-DNA gels, this phenomenon is more complicated. The dynamical behavior of water of hydration in DNA gels is thus concluded to be different among counterion species. [ABSTRACT FROM AUTHOR]

We numerically investigated signals from a scanning near-field optical microscope (NOM) for samples of various sizes by using the finite-difference time-domain method. Under the usual conditions that apply to detection, the signal intensity depends on the width of the sample, even though the sample will be wider than the wavelength, which is much larger than the aperture, i.e., the lateral resolution of the NOM. This is an obstacle to measuring the local optical constant of samples by means of obtaining the signal intensity. When waves propagating in all directions are collected, this dependence on the sample width is reduced. The whole angle detection is important for observing the distribution of the optical constants. OCIS codes: 170.0180, 120.3150, 120.4640.

Cultivated strawberry (Fragaria x ananassa) is octoploid and shows allogamous behaviour. The present study aims at dissecting this octoploid genome through comparison with its wild relatives, F. iinumae, F. nipponica, F. nubicola, and F. orientalis by de novo whole-genome sequencing on an Illumina and Roche 454 platforms. The total length of the assembled Illumina genome sequences obtained was 698 Mb for F. x ananassa, and ∼200 Mb each for the four wild species. Subsequently, a virtual reference genome termed FANhybrid_r1.2 was constructed by integrating the sequences of the four homoeologous subgenomes of F. x ananassa, from which heterozygous regions in the Roche 454 and Illumina genome sequences were eliminated. The total length of FANhybrid_r1.2 thus created was 173.2 Mb with the N50 length of 5137 bp. The Illumina-assembled genome sequences of F. x ananassa and the four wild species were then mapped onto the reference genome, along with the previously published F. vesca genome sequence to establish the subgenomic structure of F. x ananassa. The strategy adopted in this study has turned out to be successful in dissecting the genome of octoploid F. x ananassa and appears promising when applied to the analysis of other polyploid plant species. [ABSTRACT FROM PUBLISHER]