Phenotypic plasticity of life history characteristics: quantitative analysis of delayed reproduction of green foxtail (Setaria viridis) in the Songnen Plain of China

Green foxtail (Setaria viridis L,) is a common weed species in temperate regions. Research on the effect of delayed reproduction on the phenotypic plasticity and regularity of the vegetative and reproductive growth is of vital significance for understanding population regulation and control of the weed in the growing season, Green foxtail seeds were sown every 10 days from 25 June to 24 August of 2004. The growth and production metrics were measured via harvesting tufts and statistical analysis was carried out. The results showed that the reproductive tillers, seed number, seed biomass and one thousand-seed weight of plants at the first sowing (25 June) approximately increased 28.8, 7827.0, 1104.0 and 12.3 times compared with that at the last sowing (24 August), respectively. Total tillers, reproductive tillers and height increased linearly as the reproductive period delayed, however, biomass increased exponentially. Quadratic equations best explained the relationships between the delayed reproductive period and seed number, Inflorescence length, one thousand-seed weight, seed biomass. Based on the quantity and quality of seed production, weeding young seedlings emerging before July can be the most effective weed-control strategy in the Songnen Plain.     

青狗尾草RNAi途径相关基因的全基因组鉴定和表达分析

RNAi途径是RdDM途径的衍生途径,其中的AGO、DCL和RDR蛋白在植物的生长发育和响应非生物/生物胁迫过程中发挥重要作用。为了研究RNAi途径的3种主要蛋白在青狗尾草中的序列及结构特征,利用比较基因组学方法,在青狗尾草中鉴定到13个AGO基因、7个DCL基因和4个RDR基因,并对其蛋白质亚细胞定位、系统发育关系、保守结构域进行预测。同时,利用转录组数据分析RNAi途径的3类相关基因在青狗尾草的16种不同生长时期、不同生长条件下的表达模式。蛋白质结构域分析发现,SvDCL3b和SvRDR3缺少重要的结构域。转录组分析发现,SvAGO1b、SvDCL1a和SvRDR1在各家族中表达量较高,可能在RNAi途径中发挥主要作用,且大多数青狗尾草和谷子的同源基因间的表达模式基本一致。综上,本研究为理解RNAi途径的3种主要基因在调控青狗尾草的表观遗传修饰中的功能和作用提供初步的理论依据,为青狗尾草和谷子之间驯化的分子机制提供 参考。     

谷子肌动蛋白基因的克隆及序列分析

以谷子 (Setariaitalica)为材料 ,提取总RNA。根据植物肌动蛋白基因编码区的两端的保守序列设计了简并引物 ,用 5’RACE方法扩增出了谷子肌动蛋白基因编码区序列。以豌豆肌动蛋白cDNA作探针进行的Southern杂交分析表明扩增出了目的基因。将所获得的片段克隆到T载体后进行测序 ,序列分析结果表明 :谷子肌动蛋白基因的编码区长 1 1 3 1个核苷酸 ,编码了 3 77个氨基酸 ;所得序列 (命名为MIAc)与GenBank中注册的肌动蛋白基因序列的相似性均在 6 0 %以上 ,与其它肌动蛋白氨基酸序列的相似性达 89%以上。根据高等植物肌动蛋白序列相似性重建了进化树 ,表明谷子肌动蛋白与水稻肌动蛋白异型体RAc2和RAc3之间的亲缘关系最为密切 ,在进化过程中分化时间最为接近     

谷子窄颖花突变体sins1的表型分析和突变基因定位

利用甲基磺酸乙酯(EMS,ethyl methyl sulfonate)诱变剂处理野生型Yugu1(豫谷1号),在后代中发现了一个可以稳定遗传的颖花明显变窄的突变体,将其命名为sins1。与Yugu1相比,突变体sins1的株高显著降低了3.89%,穗长和穗粗分别显著降低了17.42%和21.62%,旗叶叶长和叶宽分别显著降低了15.09%和25.78%,千粒重显著降低了40.96%,谷码数显著降低了25%,均达到显著水平(P0.05)。利用突变体sins1为母本、SSR41为父本构建F_2定位群体,F_2正常颖花与窄颖花植株数目的分离比例为3∶1,表明该突变性状由隐性单基因控制。利用F_2群体隐性单株,最终将突变基因定位在3号染色体上SSR标记3-2658与CAAS3031间约7.709 Mb的距离内,为下一步精细定位提供了基础,同时也为促进禾本科作物颖花的研究提供了方向。     

Phytoliths Analysis for the Discrimination of Foxtail Millet (Setaria italica) and Common Millet (Panicum miliaceum)

Foxtail millet (Setaria italica) and Common millet (Panicum miliaceum) are the oldest domesticated dry farming crops in Eurasia. Identifying these two millets in the archaeobotanical remains are still problematic, especially because the millet grains preserve only when charred. Phytoliths analysis provides a viable method for identifying this important crop. However, to date, the identification of millet phytoliths has been questionable, because very little study has been done on their morphometry and taxonomy. Particularly, no clear diagnostic feature has been used to distinguish between Foxtail millet and Common millet. Here we examined the anatomy and silicon structure patterns in the glumes, lemmas, and paleas from the inflorescence bracts in 27 modern plants of Foxtail millet, Common millet, and closely related grasses, using light microscopy with phase-contrast and microscopic interferometer. Our research shows that five key diagnostic characteristics in phytolith morphology can be used to distinguish Foxtail millet from Common millet based on the presence of cross-shaped type, regularly arranged papillae, Ω-undulated type, endings structures of epidermal long cell, and surface ridgy line sculpture in the former species. We have established identification criteria that, when used together, give the only reliable way of distinguishing between Foxtail millet and Common millet species based on their phytoliths characteristics, thus making a methodological contribution to phytolith research. Our findings also have important implications in the fields of plant taxonomy, agricultural archaeology, and the culture history of ancient civilizations.     

Occurrence and effectiveness of an indigenous strain of Myrothecium roridum Tode: Fries as a bioherbicide for water hyacinth (Eichhornia crassipes) in Nigeria

In a study to isolate fungal pathogens with potential for the biocontrol of water hyacinth (Eichhornia crassipes), some lakes in the Lagos State and its environs, Nigeria, were surveyed for diseased water hyacinth (E. crassipes). The fungi present in the diseased tissue were isolated and identified as: Aspergillus niger, Aspergillus flavus, Penicillium sp., Curvularia pallescens, Fusarium solani and Myrothecium roridum. The pathogenicity of isolates of these fungi on fresh, non-diseased water hyacinth plants was investigated. Myrothecium was the only species capable of inducing disease symptoms. Necrosis was observed on water hyacinth leaves three days post inoculation (DPI) with M. roridum (1 × 10⁶ spores/ml). The leaves and the petioles were withered at the end of day 24, and the disease incidence and disease severity were 100% and 8.67%, respectively. Molecular analysis of the internal transcribed spacer rDNA of the M. roridum isolate from water hyacinth showed >98% homology to authenticated sequences of M. roridum. The isolate, deposited at the International Mycological Institute, UK, as M. roridum Tode: Fries (IMI 394934), possesses the level of virulence needed in a potential mycoherbicide for use in the management of water hyacinth.     

New polymorphic microsatellite markers and development of mitotyping primers for West Mediterranean green toad species (Bufo viridis subgroup)

We report new polymorphic microsatellites for three species of Palearctic green toads (Bufo viridis subgroup): 10 in B. balearicus and seven each in B. siculus and B. boulengeri. Diversity at these loci, measured for 27 B. balearicus, 23 B. siculus and 11 B. boulengeri, ranged from low to high (two to 10 alleles). Mitotyping primers, specific to the control region, which allow fast screening of parapatric Sicilian endemic B. siculus and Italian mainland-origin B. balearicus, were developed.     

Laboratory biology and impact of a stem-boring weevil Apocnemidophorus pipitzi (Coleoptera: Curculionidae) on Schinus terebinthifolia

Brazilian peppertree, Schinus terebinthifolia Raddi (Anacardiaceae), was introduced into Florida, USA, from South America as an ornamental plant in the late 19th and early 20th centuries. It eventually escaped cultivation and is a serious threat to the state’s biodiversity. In the 1980s, this invasive weed was targeted for classical biocontrol. Surveys for natural enemies of Brazilian peppertree conducted in the native range resulted in the discovery of several candidate biocontrol agents. A stem-boring weevil identified as Apocnemidophorus pipitzi (Faust) was collected in Paraguay and transported under permit to Florida, USA. A laboratory colony of A. pipitzi was established in April 2007 by caging adults on cut branches of Brazilian peppertree supplemented with leaf bouquets. Adults are defoliators that feed mainly on the upper surface of subterminal leaflets. Females deposit eggs singly inside the stems and larvae feed under the bark where they damage the vascular cambium. There are five instars, pupation occurs inside the stem and a new generation is produced in 3–4 months. Growth of potted plants with and without exposure to weevil herbivory was compared over an 11-month period. Feeding damage by adults and larvae significantly increased leaf abscission and reduced leaf and root biomass accumulation.     

Morphological and molecular characterization of populations of plains bristlegrass (<i>Setaria macrostachya</i> Kunth) in Chihuahua,México

Plains bristlegrass (Setaria macrostachya Kunth) is a native grass with forage value. However, due to the lack of grazing management practices, populations and thus genetic diversity, have been reduced. Morphological and genetic variability were analyzed on 44 populations of plains bristlegrass in the State of Chihuahua. Plants were transplanted in a common area under natural conditions. Two years later, morphological characterization was evaluated measuring nine variables, and genetic variability using AFLP molecular markers. The principal components analysis (PC) showed that the three first principal components explained 73.74% of the variation. The variables with the greatest contribution to the variance in PC1 were plant height and inflorescence length; in CP2, tiller number and leaf width; and in PC3, tiller thickness. Application of four pairs of primers, presented 186 total bands, from which 87.10% showed polymorphism and 12.90% monomorphism. The combination of EcoRI-AGG MseI-CAG primers detected the highest percentage (93%) of polymorphism with 40 polymorphic bands. The cluster analysis and Dice coefficient indicated that populations clump into two groups. The wide genetic variability and morphological characteristics detected among populations represent the basis for the selection of populations that could be used with different purposes in the rehabilitation of ecosystems. In addition, this study will allow establishment of in situ conservation strategies.     

Evaluation of the bioherbicide Myrothecium verrucaria for weed control in tomato (Lycopersicon esculentum)

An isolate of the fungus Myrothecium verrucaria was evaluated for its biocontrol potential against common purslane, horse purslane, spotted spurge, and prostrate spurge, all serious weed pests in commercial tomato fields in the southeastern US. In greenhouse and field tests, M. verrucaria was highly virulent against these weeds when applied as conidial sprays formulated in 0.2% Silwet L-77 surfactant, even in the absence of dew. In field test plots naturally infested with these weeds, seedlings in the two-to-three leaf growth stage treated with M. verrucaria at 2×10⁷ conidia mL^-1 in 0.2% Silwet, exhibited leaf and stem necrosis within 24 h following inoculation, with mortality occurring within 96 h. After 7 days, M. verrucaria had killed 90-95% of both purslane species and 85-95% of both spurge species. Tomatoes that were transplanted into plots treated with M. verrucaria remained healthy and vigorous throughout the growing season. Since M. verrucaria effectively controlled several common weeds under field conditions, this fungus appears to have potential as an effective bioherbicide for pre-plant weed control in production systems with transplanted tomato.     

Relation between in vitro production of ascosonchine and virulence of strains of the potential mycoherbicide Ascochyta sonchi: a method for its quantification in complex samples

The potential of the fungus Ascochyta sonchi as a mycoherbicide for the biocontrol of the perennial weeds Sonchus arvensis and Cirsium arvense that occur throughout temperate regions of the world is under evaluation. Ascosonchine, a newly discovered enol tautomer of 4-pyridylpyruvic acid with potential herbicidal properties, is the main phytotoxin produced by this fungus. A simple and sensitive method has been developed for the rapid quantitative analysis of ascosonchine based on HPLC with UV detection. The toxin content in culture filtrates of different strains of A. sonchi was measured. The strains tested produced up to 2.7 mg/L when grown in static conditions. Toxin production was compared with the virulence on the host plant of each strain to determine if the most virulent strains could be simply selected by choosing the best toxin producers. The results obtained do not support this approach. The same HPLC method was also applied to quantify toxin production under different fungal growth conditions, in order to achieve the highest toxin production. The most productive strain synthesised more than 8 mg/L when grown for 8 weeks in static conditions.     

Distribution, biology and host range of Rhembastus sp. (Coleoptera: Chrysomelidae), a candidate for the biological control of Bryophyllum delagoense (Crassulaceae) in Australia

The biology and host range of a leaf-beetle, Rhembastus sp. (Coleoptera: Chrysomelidae: Eumolpinae) from Madagascar, was studied under quarantine laboratory conditions in South Africa to determine its potential as a biological control agent of Bryophyllum delagoense (Ecklon & Zeyher) Schinz (Crassulaceae) in Australia. Favourable attributes of the beetle include relative ease of culturing, multiple generations per year, and high levels of damage inflicted by adults, which feed on the plantlets produced at the end of each leaf, and root feeding larvae. The adults therefore have an impact on the reproductive potential of the plant and larval feeding on the roots hampers the uptake of water and may even facilitate secondary infections by pathogens. Despite indications from field surveys in Madagascar that Rhembastus sp. has a narrow host range, preliminary no-choice and multiple-choice trials in quarantine revealed that it could complete its development on five non-target species in the family Crassulaceae. Extensive host range trials still have to be undertaken in Australia before the beetle can be considered for release.     

Influence of release size on establishment and impact of a root weevil for the biocontrol of houndstongue (Cynoglossum officinale)

The root-boring weevil, Mogulones cruciger, was introduced into Canada to control the weed, houndstongue (Cynoglossum officinale). To optimise its use as a biocontrol agent, a 2-year study was performed in British Columbia, Canada to test if the number of M. cruciger released at sites predicted subsequent declines in weed populations. No, 100, 200, 300 or 400 weevils were released in 1999 at field sites (five replicates) corresponding to discrete populations of houndstongue separated by distances of 0.3–3 km. The sites were subsequently monitored for weevil establishment, population change, and host attack, and houndstongue population change. By 2001, M. cruciger had established at all 20 release sites and was present in low numbers in three of five control sites. The year following release, release size was positively correlated with number of adult weevils collected, their damage to host plants, and with subsequent numbers of larvae per plant. In contrast, houndstongue populations were reduced at the same rate and amount, regardless of the experimental release size, within 2 years of release. Significant release treatment×time interactions indicated that factors other than M. cruciger contributed to houndstongue reductions (e.g. drought). However, overall the addition of weevils accelerated the reductions relative to sites with no weevils added. Our study demonstrated that the lowest number within a range of release sizes typically used in weed biocontrol programmes (i.e. 100) was as effective as 200–400 weevils in achieving a consistent amount and rate of houndstongue reduction, and thus, could be implemented to optimise weevil use and achieve predictable biocontrol.     

Effect of temperature on the survival of Aconophora compressa Walker (Hemiptera: Membracidae): implications for weed biocontrol

Abstract  In weed biocontrol, similarity of abiotic factors between the native and introduced range of a biocontrol agent is critical to its establishment and effectiveness. This is particularly the case for weeds that have a wide geographical distribution in the native range. For such weeds, the choice of a specialist insect that has narrow tolerance limits to important abiotic factors can diminish its ability to be an effective biocontrol agent. The membracid Aconophora compressa was introduced in Australia from Mexico for biocontrol of Lantana camara , a plant with a wide climatic tolerance. In this study we investigated the effect of constant and alternating temperatures on A. compressa survival. Longevity of adults and nymphs declined with increasing temperatures, and at 39°C individuals survived for less than a day. At lower temperatures, nymphs survived longer than adults. Survival at alternating temperatures was longer than at constant temperatures, but the general trend of lower survival at higher temperatures remained. Spatially and temporally, the climatic tolerance of A. compressa appears to be a subset of that of lantana, thereby limiting its potential impact.     

Phylogeography of the poison frog Mantella viridis (Amphibia: Mantellidae) reveals chromatic and genetic differentiation across ecotones in northern Madagascar

Mantella viridis is a threatened poison frog species endemic to the ecologically very heterogeneous northern region of Madagascar. The existence of several colour morphs within M. viridis and its very low genetic differentiation to the allopatrically distributed Mantella ebenaui raise questions about the processes driving the differentiation between these poison frog populations and about their taxonomic status. Using a DNA fragment of 476 nucleotides of the mitochondrial cytochrome b gene from 240 individuals of this species complex, we investigated the genetic variability of all known colour morphs of M. viridis, sampling this species throughout its known range, as well as several populations of M. ebenaui. Our genetic results confirm that M. viridis and M. ebenaui are closely related but reveal that no haplotype sharing occurs between these two taxa. Further, our molecular analyses provided evidence for barriers to gene flow among some of the colour morphs. Estimates of overlap of bioclimatic envelopes as assessed by ecological niche modelling also suggest a distinct bioclimatic niche of some of the lineages studied.     

Biological studies of the Australian predatory mite Typhlodromips montdorensis (Schicha) (Acari: Phytoseiidae), a potential biocontrol agent for western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae)

Abstract The biology of the Australian phytoseiid mite Typhlodromips montdorensis is described from material collected in Queensland and South Australia in 1994−1996. At 25°C, when fed on cumbungi ( Typha sp.) pollen, the life cycle was completed in approximately 7 days, with an intrinsic rate of natural increase ( r _m ) of 0.32. Female−male pairs produced a mean total of 52.7 eggs within 28 days of oviposition. Females that were deprived of males after first mating stopped laying eggs after 7−19 days; however, if another male was added, they resumed egg laying and produced, on average, a total of 49.4 eggs. The sex ratio was 2.24 females to one male. At 25°C, fecundity on a diet of thrips larvae (first-instar Frankliniella schultzei Trybom) was high, ranging from 2.72 to 3.58 eggs per day on the third day, depending on previous diet. Consumption rate of thrips was also high, with an average of 7.23−14.44 first-instar larvae eaten per day on the third day, depending again on previous diet and also on number of thrips larvae made available. The species was also observed to feed on: (i) broad mite, Polyphago­tarsonemus latus (Banks); (ii) tomato russet mite, Aculops lycopersici (Massee); and (iii) two-spotted mite, Tetranychus urticae Koch. No diapause was observed under conditions of 25°C, 8 h light and 10°C, 16 h dark. Eggs were sensitive to low humidity, with 50% failing to hatch below 70.8% relative humidity. This species is of interest as a candidate biological control agent for thrips, broad mite and tomato russet mite in protected crops.     

Prevalence and infection intensity of the biocontrol agent Paranosema locustae (Microsporidia) in field-collected,newly-associated hosts (Orthoptera: Acrididae: Melanoplinae)

Host range, prevalence, and infection intensity of Paranosema locustae in grasshoppers at an establishment site in Patagonia, Argentina, were recorded. Results agreed with earlier observations at other introduction-establishment areas. Affected grasshoppers were melanoplines (Baeacris punctulatus, Dichroplus elongatus, Dichroplus maculipennis). Sporulation was not observed in instars I, II, and III.     

Green Synthesis of Bimetallic Nanoparticles From Prosopis juliflora (Sw) DC., and Its Effect Against Cotton Mealybug,Phenacoccus solenopsis (Hemiptera: Pseudococcidae)

Phenacoccus solenopsis has been recognized as an aggressively invasive species on cotton plants in different countries. This study was conducted to investigate the effect of green synthesized Cu/Zn-nanoparticles using aqueous leaf extract of Prosopis juliflora (mezquite) against P. solenopsis. The scanning electron microscope (SEM) showed bimetallic nanoparticles of Cu/Zn-NPs with spherical shape with varying size of 74.33 nm to 59.46 nm. More than 30% mortality of P. solenopsis was observed with Cu/Zn-nanoparticles (100 ppm) at 96 hours after treatment. Negligible mortality of P. solenopsis was recorded with Cu/Zn solution (100 ppm) and aqueous P. juliflora extracts. The results of the viability test for Cu/Zn-nanoparticles of P. juliflora showed a significant reduction of the cell viability by 50% in insect exposed to Cu/Zn-nanoparticles-P.juliflora. Therefore studies about nanotoxicity of Cu/Zn-NPs of P.juliflora are needed to reveal the mechanism of toxicity this phytonanoparticles in P.solenopsis.     

Laboratory investigations on the potential of entomopathogenic fungi for biocontrol of Helicoverpa armigera (Lepidoptera: Noctuidae) larvae and pupae

The susceptibility of third instar Helicoverpa armigera to seven strains of three entomopathogenic fungal species, i.e. Metarhizium anisopliae, Beauveria bassiana and Paecilomyces fumosoroseus, was tested under laboratory conditions using the larval immersion method. High efficacies ranging from 68 to 100% corrected mortality were recorded with more profound effects in treatments with B. bassiana and P. fumosoroseus strains. The median lethal concentration (LC₅₀) for L3 was 6.0×10⁵ in M. anisopliae 79, 1.5×10⁵ in B. bassiana 124 and 4.2×10⁴ in P. fumosoroseus 14. These three strains were further used to characterize the age-dependent mortality of different larval stages (L2-L5) and the effect against pupae of H. armigera. Larval stages did not differ in their mortality but differed i in median lethal time, with shorter values recorded in the second instar. Tested fungi also caused a high reduction between 74.4 and 100% in the emergence of pupae using the soil inoculation method and the pupal immersion technique. All three fungal species, especially P. fumosoroseus, have a high potential for biocontrol of H. armigera larvae and also as a soil treatment targeting the pupae.     

Accumulation of Ag, Cd, Co, Cu, Hg, Ni and Pb in Pavlova viridis Tseng (Haptophyceae)

The flagellate alga Pavlova viridis Tseng was investigated in the laboratory for accumulation of the heavy metals, silver, cadmium, cobalt, copper, mercury, nickel and lead. The cultures were grown in an artificial seawater medium mixed with the individual metals at different concentrations. Based on data from the controls, the baseline metal concentrations in P. viridis were shown to be in an order of Cu > Pb > Co > Cd > Ni > Ag > Hg. In the experimental groups, the seven metals displayed different isotherm equilibrium patterns and the metal uptake capacity of the alga was Ni > Pb > Co > Hg > Cu > Cd > Ag at equilibrium. When assessed using the bioconcentration factors, metal accumulation by P. viridis was demonstrated to be the most efficient at a concentration of 0.001 mg L-1 for Ag, Cd and Co, and at 0.01 mg L-1 for Cu, Hg, Ni and Pb. This study suggests that P. viridis can be a source of mineral supplements in mariculture. The alga is not, however, recognized as an effective agent for removing heavy metals from wastewater. This revised version was published online in June 2006 with corrections to the Cover Date.