Differential response of pea (Pisum sativum) to Orobanche crenata, Orobanche foetida and Phelipanche aegyptiaca

Several broomrape species including Orobanche crenata, Orobanche foetida and Phelipanche aegyptiaca are reported to infect various grain and forage legumes in the Mediterranean and West Asia. Pea (Pisum sativum) is severely damaged by O. crenata, but there are no reports on O. foetida or P. aegyptiaca infection. We report here that pea can induce high germination of seeds of O. crenata, O. foetida and P. aegyptiaca but only O. crenata success infecting pea roots and developing further. Some differences in levels of infection by O. crenata were observed among pea accessions what can be exploited in pea resistance breeding programmes. On the contrary, all pea accessions studied were highly resistant to infection by both O. foetida and P. aegyptiaca, preventing any tubercle attachment and development. This makes pea a promising candidate as trap crop for O. foetida and P. aegyptiaca seed bank demise in infested soils.     

Inter-cropping with berseem clover (Trifolium alexandrinum) reduces infection by Orobanche crenata in legumes

Grain legume production in the Mediterranean area is threatened by the holoparasitic plant Orobanche crenata to which little resistance is available in affected crops. Berseem clover is a forage legume of economic importance in Eastern Mediterranean region and tropical areas. It has been suggested as a suitable trap crop for controlling O. crenata. In this work we propose its use as an inter-crop with grain legumes. We describe its allelopathic activity against germination of O. crenata seeds. Results are supported by three years of field experimentation in Egypt with a significant reduction of O. crenata infection on faba bean and pea inter-cropped with berseem clover. Mini-rhizotron experiments demonstrated the reduction of O. crenata infection on pea, lentil and chickling pea.     

Discrimination of sterile oat (Avena sterilis) in winter barley (Hordeum vulgare) using QuickBird satellite images

Site-specific weed management implies detecting the location of weeds in order to generate maps of their spatial distribution. This information facilitates a more accurate application of herbicides, spraying them in the exact areas of weed growth and in the required doses. In order to explore the potential of commercial satellites to discriminate and map weeds, we used the information contained in high spatial resolution images acquired by the QuickBird satellite to assess the density of sterile oat (Avena sterilis) present in a winter barley field at two different dates (March and June). Our results confirmed the potential of using satellite images in the spectral discrimination of weed patches in infested fields. The results of binary logistic regressions showed that the best matches in the classification of three categories (low, medium, or high sterile oat densities) corresponded to the March image. QuickBird’s March image provided reliable estimates of sterile oat patches in barley crops when weed density was relatively high (between 86% and 94% of agreement between predicted and observed densities). However, when weed densities were lower than 10 plants/m² there were serious difficulties to distinguish them from weed-free zones (between 72 and 75% of global agreement in the classification) with large underestimation of medium density weed patches (10 plants/m²). This is a potential limitation considering than the thresholds used for herbicide application decisions are generally close to this density. However, the information obtained may still be useful for producing field maps to describe the spatial distribution of this weed. Moreover, these studies have provided valuable information on the best spectral regions and/or vegetation indices for approaching discrimination between sterile oat and cereal crops and the most suitable period for it.     

Spatiotemporal Distribution of Chinavia hilaris (Hemiptera: Pentatomidae) in Peanut-Cotton Farmscapes

The green stink bug, Chinavia hilaris (Say) (Hemiptera: Pentatomidae), is a pest of cotton in the southeastern United States, but little is known concerning its spatiotemporal distribution in agricultural farmscapes. Therefore, spatiotemporal distribution of C. hilaris in farmscapes where cotton fields adjoined peanut was examined weekly. Spatial patterns of C. hilaris counts were analyzed using SADIE (Spatial Analysis by Distance Indices) methodology. Interpolated maps of C. hilaris density were used to visualize abundance and distribution of C. hilaris in crops. For the six peanut-cotton farmscapes studied, the frequency of C. hilaris in cotton (94.8%) was significantly higher than in peanut (5.2%), and nymphs were rarely detected in peanut, indicating that peanut was not a source of C. hilaris into cotton. Significantly, aggregated spatial distributions were detected in cotton. Maps of local clustering indices depicted patches of C. hilaris in cotton, mainly at field edges including the peanut-to-cotton interface. Black cherry (Prunus serotina Ehrh.) and elderberry (Sambucus nigra subsp. canadensis [L.] R. Bolli) grew in habitats adjacent to crops, C. hilaris were captured in pheromone-baited stink bug traps in these habitats, and in most instances, C. hilaris were observed feeding on black cherry and elderberry in these habitats before colonization of cotton. Spatial distribution of C. hilaris in these farmscapes revealed that C. hilaris colonized cotton field edges near these two noncrop hosts. Altogether, these findings suggest that black cherry and elderberry were sources of C. hilaris into cotton. Factors affecting the spatiotemporal dynamics of C. hilaris in peanut-cotton farmscapes are discussed.     

Genetic stability of long-term micropropagated Opuntia ficus-indica (L.) Mill. plantlets as assessed by molecular tools: Perspectives for in vitro conservation

Randomly amplified polymorphic DNA markers (RAPD) were employed to assess the level of genetic stability of long term micropropagated prickly pear (Opuntia ficus-indica) plantlets.Thirteen micropropagated plantlets were chosen from a clonal collection of shoots that originated from a single mother shoot. This clonal collection had been maintained under in vitro culture conditions for at least 5 years, as achieved for the time by axillary branch multiplication in Opuntia ficus-indica.Twenty arbitrary primers were used to compare RAPD patterns between in vitro raised material and the mother plant. Only 11 primers were found to yield distinct and reproducible amplification products resulting in a total of 87 amplified products, out of which 82 bands were monomorphic across all the plantlets and 5 showed polymorphisms.Cluster analysis performed on the basis of similarity indices indicated that all micropropagated plantlets and their mother plant grouped together in one major cluster with a 91% level of similarity.Low level of genetic variation has been detected, as polymorphic bands accounted for just 2.79% of the total genetic variation. This very low level of genetic variation, despite more than 5 years of in vitro culture, demonstrates the genetic stability of Opuntia ficus-indica and indicates that the axillary branch multiplication method is highly reliable for the multiplication of genetically true-to-type plant material.The high degree of clonal fidelity detected here, recommend the use of axillary-branching micropropagation technique for the safe in vitro conservation of prickly pear interesting genetic resources.     

Field response of Lathyrus cicera germplasm to crenate broomrape (Orobanche crenata)

Crenate broomrape (Orobanche crenata Forks.) is a major constraint for grain and forage legume cultivation in Mediterranean agriculture, to which little resistance is available. We studied the response to O. crenata of a germplasm collection of chickling pea (Lathyrus cicera L.) in field trials over two seasons showing that resistance although scarce and masked by confounding factors, is available and can be used in breeding. The level of infection was highly influenced by environmental factors and plant growth cycle. Earlier accessions were less infected due to competition of the earlier settled pods with O. crenata tubercles. O. crenata infection strongly reduced host biomass and grain yield. Deviations from the polynomic regression gave an improved approximation of the true genetic resistance levels present in the germplasm.     

Spatial and Temporal Dynamics of Stink Bugs in Southeastern Farmscapes

A 3-yr study (2009–2011) was conducted to examine the spatial and temporal dynamics of stink bugs in three commercial farmscapes. Study locations were replicated in South Carolina and Georgia, in an agriculturally diverse region known as the southeastern coastal plain. Crops included wheat, Triticum aestivum (L.), corn, Zea mays (L.), soybean, Glycine max (L.), cotton, Gossypium hirsutum (L.), and peanut, Arachis hypogaea (L.). Farmscapes were sampled weekly using whole-plant examinations for corn, with all other crops sampled using sweep nets. The predominant pest species of phytophagous stink bugs were the brown stink bug, Euschistus servus (Say), the green stink bug, Chinavia hilaris (Say), and the southern green stink bug, Nezara viridula (L.). Chi-square tests indicated a departure from a normal distribution in 77% of analyses of the variance to mean ratio, with 37% of slopes of Taylor’s power law and 30% of coefficient β of Iwao’s patchiness regression significantly greater than one, indicating aggregated distributions. Spatial Analyses by Distance IndicEs (SADIE) indicated aggregated patterns of stink bugs in 18% of year-end totals and 42% of weekly counts, with 80% of adults and nymphs positively associated using the SADIE association tool. Maximum stink bug densities in each crop occurred when the plants were producing fruit. Stink bugs exhibited greater densities in crops adjacent to soybean in Barnwell and Lee Counties compared with crops adjacent to corn or fallow areas. The diversity of crops and relatively small size of fields in the Southeast leads to colonization of patches within a farmscape. The ecological and management implications of the spatial and temporal distribution of stink bugs within farmscapes are discussed.     

Understanding of relationships between ground cover and rat abundances: An integrative approach for management of the oil palm agroecosystem

Ground cover is an essential element in the selection of habitats by small mammals. It provides shelter, foraging opportunities and a hiding place from predators. In oil palm plantations rodents are abundant yet the relationships between ground cover structure and rats are not well understood. Plantation management emphasizes maximisation of oil palm yield by reducing rat damage and competition from weeds, typically through chemical control. This study examined the relationships between ground cover, including undergrowth and frond piles, and rat abundance. Rat trapping and vegetation assessment were conducted simultaneously in five study plots in the Labu Estate, Negeri Sembilan, Malaysia. Over 21,000 trap-nights 1190 individual rats were captured and these data were analysed using spatial analysis by distance indices (SADIE). No significant clustering of rats was observed within any plot over time. Redundancy analyses suggested that the overall occurrence of rats, especially Rattus argentiventer, was positively correlated with vegetation cover and height. This implies that habitat complexity is important to rats, even in a relatively simple agroecosystem. Results of the SADIE analyses were inconsistent, perhaps due to highly variable management practices in the plantations. The findings from this study suggest that using an integrated approach in the control of both weeds and rats in oil palm plantations may maximise the benefits from weeding while reducing the production loss due to rats and the need for chemical control of rats.     

Variability in essential oil content and composition of Origanum hirtum L., Origanum onites L., Coridothymus capitatus (L.) and Satureja thymbra L. populations from the Greek island Ikaria

Plants belonging to four “oregano” plant species (Origanum hirtum L., Origanum onites L., Coridothymus capitatus L., and Satureja thymbra L.) were collected during flowering from 33 sites located in the eastern part of the Greek island of Ikaria in the Eastern Aegean during April, May and July 2008. C. capitatus and O. hirtum were mostly observed in higher altitudes, whereas O. onites and S. thymbra in lower ones. The spatial distribution of all species was depicted on a GIS map. All four species exhibited essential oil concentrations higher than those reported in earlier literature, namely O. onites 3-4.3%, S. thymbra 4-6.5%, C. capitatus 3.7-5.6% and O. hirtum 5.5-10.0% (v/w). Carvacrol was the main constituent of the essential oils of all species, followed by γ-terpinene, p-cymene and caryophyllene, while thymol was not detected. All constituents varied remarkably among the four species, with carvacrol exhibiting the lowest variation. Carvacrol content varied between 72.3 and 89.2% in O. onites; 46.5 and 58.0% in S. thymbra; 82.9 and 90.9% in C. capitatus; and 84.4 and 93.8% in O. hirtum. By applying hierarchical cluster analysis on the basis of the essential oil constituents two main groups, divided into four subgroups of the taxa were evident. The first group consisted of O. onites and S. thymbra, while the second one of C. capitatus and O. hirtum. The results are discussed in terms of topography and climatic variation.     

Spatiotemporal Distribution of Chinavia hilaris (Hemiptera: Pentatomidae) in Corn Farmscapes

The green stink bug, Chinavia hilaris (Say) (Hemiptera: Pentatomidae), is a pest of cotton in the southeastern United States but little is known concerning its spatiotemporal distribution in corn cropping systems. Therefore, the spatiotemporal distribution of C. hilaris in farmscapes, when corn was adjacent to cotton, peanut, or both, was examined weekly. The spatial patterns of C. hilaris counts were analyzed using Spatial Analysis by Distance Indices methodology. Interpolated maps of C. hilaris density were used to visualize abundance and distribution of C. hilaris in crops in corn–peanut–cotton farmscapes. This stink bug was detected in six of seven corn–cotton farmscapes, four of six corn–peanut farmscapes, and in both corn–peanut–cotton farmscapes. The frequency of C. hilaris in cotton (89.47%) was significantly higher than in peanut (7.02%) or corn (3.51%). This stink bug fed on noncrop hosts that grew in field borders adjacent to crops. The spatial distribution of C. hilaris in crops and the capture of C. hilaris adults and nymphs in pheromone-baited traps near noncrop hosts indicated that these hosts were sources of this stink bug dispersing into crops, primarily cotton. Significant aggregated spatial distributions were detected in cotton on some dates within corn–peanut–cotton farmscapes. Maps of local clustering indices depicted small patches of C. hilaris in cotton or cotton–sorghum at the peanut–cotton interface. Factors affecting the spatiotemporal dynamics of C. hilaris in corn farmscapes are discussed.     

Spatial variability of switchgrass (Panicum virgatum L.) yield as related to soil parameters in a small field

The harvested biomass of switchgrass (Panicum virgatum L.) is generally much lower than its potential; this may be due to several factors including not recovering all the biomass at harvest, weed competition, pests, disease and spatial variation of soil features. The objective of this research was to quantify the yield spatial variation of switchgrass and relate it to soil parameters, in a field of about 5 ha, in 2004 and 2005. Several thematic maps of soil parameters and biomass yield were produced using GIS and geostatistical methods. Soil parameters changed consistently within very short distances and biomass yield varied from 3 to more than 20 Mg ha⁻¹. This remarkable variation indicates that the potential for increasing switchgrass productivity is a real prospect. Furthermore, spatial variation of yield showed similar patterns in the 2 years (r = 0.38^**), and therefore a major influence of site characteristics on switchgrass yield can be assumed to occur. Significant correlations were found between biomass yield and soil N, P, moisture and pH as well as between soil parameters. Some soil parameters such as sand content showed patchy spatial distribution. Conversely, a reliable spatial dependence could not be identified for other parameters such as P. Further research is needed.     

An SNP downstream of the OsBEIIb gene is significantly associated with amylose content and viscosity properties in rice (Oryza sativa L.)

Allele mining in starch synthesis-related genes (SSRGs) has facilitated the discovery of desired natural sequence variations for eating quality in rice. This study investigated the sequence variations from 10 SSRGs, and further evaluated their relationship with the amylose content (AC) and rapid viscosity analysis profiles in a global collection of rice accessions by association mapping (AM). In total, 83 sequence variations were found in 10 sequenced amplicons, including 73 single nucleotide polymorphisms (SNPs), eight insertion-deletions (InDels) and two polymorphic simple sequence repeats (SSRs). Four subpopulations were identified by population structure analysis based on 170 genome-wide SSR genotypes. AM revealed 11 significant associations between three phenotypic indices and three sequence variations. One SNP with a g/c transversion at the 63rd nucleotide downstream of the OsBEIIb gene termination codon on rice chromosome 2 was significantly associated with multiple trait indices in both the general linear and mixed linear models (GLM and MLM), including the final viscosity (p < 0.001, R² = 23.87%) in both 2009 and 2010, and AC (p < 0.01, R² = 11.25%) and trough viscosity (p < 0.01, R² = 20.43) in 2010. This study provides a new perspective of allele mining for breeding strategies based on marker-assisted selection.     

小麦吸浆虫幼虫在麦穗上的危害特点及空间分布型研究

为了解小麦吸浆虫幼虫在麦穗上的危害特点及在麦田的空间分布型,在春季越冬幼虫出土期选择小麦吸浆虫越冬基数不等的麦田4块,在籽粒乳熟期调查小麦吸浆虫危害程度的基础上,运用扩散系数、聚集度指标、聚集指数、平均拥挤度、聚块性指标、负二项分布参数等聚集指标及Iwao的x^*x回归法和Taylor 幂函数法,综合分析小麦吸浆虫幼虫在麦穗上的空间分布型。结果表明,小麦吸浆虫的危害程度在田块间差异很大,且危害程度与春季的幼虫越冬基数无关;在麦穗不同部位,总体趋势是上、中部受害程度大于下部,但不同田块之间有差异。以麦穗为单位时,幼虫在麦田的空间分布型属于聚集分布;以麦穗不同部位为单位时,幼虫在麦田的空间分布型也属于聚集分布,且与密度有关。聚集均数λ值的测定结果表明,小麦吸浆虫幼虫的聚集成因主要由自身的生物学特性和环境因素所决定。     

Spatiotemporal Distribution of Two Euschistus spp. Stink Bugs (Hemiptera: Pentatomidae) in Southeastern Farmscapes

Stink bugs (Hemiptera: Pentatomidae) are ubiquitous, cryptic, phytophagous pests that are found in many crops. In agroecosystems, individuals disperse from adjacent noncrop hosts and tend to aggregate or cluster within fields. In this study, we characterized the distribution of Euschistus servus (Say) and Euschistus tristigmus (Say) (Hemiptera: Pentatomidae) over 2 yr at three southeastern United States farmscapes. Stink bugs were captured in pheromone-baited traps, and Spatial Analysis by Distance Indices (SADIE) used to identify the location of significant aggregations by habitat type and season. Euschistus servus adults were more likely to be captured in pecan orchards, cotton, other crops, or unmanaged habitats than in woodland habitats. Significant aggregations of E. servus were detected in a variety of habitats including pecan, corn, cotton, peanut, and tobacco, as well as fallow and hay fields, pastures, and hedgerows. Fewer adult E. tristigmus were captured than E. servus adults, and E. tristigmus adults were typically trapped and aggregated in woodland habitats. The resulting data provide an important understanding regarding the seasonal movement and relative abundance levels of stink bug populations, which are critical to the development of integrated pest management strategies.     

Introgression of resistance to reniform nematode (Rotylenchulus reniformis) into upland cotton (Gossypium hirsutum) from Gossypium arboreum and a G. hirsutum/Gossypium aridum bridging line

Gossypium hirsutum L. is the predominant cotton of commerce and all cultivars of this species are susceptible to the reniform nematode, Rotylenchulus reniformis. To introgress resistance to R. reniformis into the tetraploid 2(AD₁) G. hirsutum, a resistant diploid A₂-genome Gossypium arboreum accession (A₂-190) was crossed with a hexaploid 2((AD₁)D₄) bridging line (G 371) to obtain a tetraploid triple-species hybrid. The triple-species hybrid was back-crossed to G. hirsutum and a population of 277 BC₁ individuals was produced. The BC₁s and controls were assayed in growth chambers for resistance to R. reniformis. Fortuitously, the hexaploid bridging line G 371 was also found to be resistant to R. reniformis. The BC₁ segregated 3:1, resistant:susceptible, indicating that resistance was conferred by dominant genes at two different loci, with each originating from a distinct germplasm source. This study demonstrated that it is possible to introgress and pyramid genes for resistance to R. reniformis in G. hirsutum.     

Spatial and temporal dynamics of Apera spica-venti seedling populations

Apera spica-venti is an important weed problem in winter cereals in Europe. Spatial and temporal dynamics of A. spica-venti were investigated to test the hypothesis that this species has a spatially aggregated distribution. A. spica-venti distribution was quantified over several crop rotation sequences in three commercial fields. From 1999 to 2006, the spatial pattern of A. spica-venti was sampled yearly at the same grid points. Geostatistical techniques were used to characterise the spatial and temporal variability of A. spica-venti density. The spatial pattern was analysed by Lloyd's index of patchiness. From year to year, differing aggregation of A. spica-venti resulted in weed patchiness. The Spearman Rank Correlation Coefficient (r_s) was used to discover the strength of A. spica-venti occurrence in several years. For two sites there were significant correlations of weed occurrence between years but the relationship was less strong for the third field. Based on rank correlation coefficients, the temporal dynamics were marked by an overall continuity of distribution patterns. Knowing that spatial distributions of weeds vary little in time can reduce sampling efforts, and increases feasibility of site-specific weed control.     

Response of spring planted barley (Hordeum vulgare L.), oats (Avena sativa L.) and wheat (Triticum aestivum L.) to mesotrione

There is little information on the response of spring planted barley (Hordeum vulgare L.), oats (Avena sativa L.) and wheat (Triticum aestivum L.) to mesotrione under Ontario environmental conditions. Four field studies were conducted in Ontario, Canada over a two-year period (2008 and 2009) to evaluate the sensitivity of spring planted cereals (barley, oats, and wheat) to pre-emergence (PRE) and post-emergence (POST) applications of mesotrione at 50, 100, and 150 g ai ha⁻¹. Mesotrione applied PRE caused minimal visible injury at 3, 7, 14 and 28 days after emergence (DAE) and had no adverse effect on plant height or yield of barley, oats and wheat. Mesotrione applied POST caused as much 11% injury and reduced plant height as much as 6% in spring planted cereals. Injury was higher in wheat compared to barley or oats. Mesotrione applied POST had no adverse effect on the yield of barley or oats but decreased the yield of wheat as much as 14%. Based on this study, mesotrione applied PRE at 50, 100 or 150 g ai ha⁻¹ can be safely used in spring planted barley, oats, and wheat. Mesotrione applied POST at the proposed dose of 50, 100 or 150 g ai ha⁻¹ can also be safely used in spring planted barley and oats. However, mesotrione applied POST results in unacceptable injury in spring planted wheat.     

Physicochemical characterization of hemicelluloses from bamboo (Phyllostachys pubescens Mazel) stem

In this paper, hemicelluloses from bamboo (Phyllostachys pubescens Mazel) stem aged six months were sequentially extracted with hot water, 2% KOH, and 5% NaOH. The water-soluble hemicelluloses H₁, and four alkali-soluble hemicellulosic fractions H₂, H₃, H₄ and H₅ were obtained, achieving a total yield of 59.60% based on the original hemicelluloses. Sugar composition analysis showed that the hemicelluloses were mainly composed of xylose (44.39-72.71%), arabinose (26.36-51.87%), ribose (0.93-2.72%), and uronic acid (0.29-5.27%). The structures of the hemicelluloses were determined to be mainly arabinoxylan, using the FT-IR and NMR techniques. The AFM images of fraction H₃ revealed a distribution of spherical nanoparticles with different sizes, while the fraction H₂ had helix rod and random coil feature. The SEM characterizations indicated that the fraction H₁ displayed spherical particles while the fraction H₃ had mainly flat particles at high magnification. Thermal stability was also analyzed using TG-DTG method and first-order kinetics model.     

Phytotoxicity of Salvia spp. exudates

A study on thirteen Salvia species about the phytotoxicity of their aerial part exudates is reported. The selected species were: Salvia namaensis Schinz (1), Salvia fallax Fernald (2), Salvia disermas L. (3), Salvia chamaedryoides Cav. (4), Salvia confertiflora Pohl. (5), S. x jamensis J.Compton (6), Salvia buchananii Hedge (7), S. wagneriana Polak (8), Salvia scabra Linn.fil. (9), Salvia miniata Fernald (10), Salvia cacaliaefolia Benth.(11), Salvia adenophora Fernald (12), Salvia rutilans Carrière (13). For each species the inhibitory potential against Papaver rhoeas L. and Avena sativa L. was evidenced by dose-response studies and growth experiments performed both in Petri dish and in pot and also evaluated by means of germination indices and growth parameters. New indices useful for describing the phytotoxic response by a reduced number of testing solutions are proposed. Principal Component Analysis (PCA) of the germination data revealed that the exudate concentrations most significant in explaining the data variability were 1 and 2 μg/mL in Petri dish and 10 and 20 μg/mL in pot experiments. Root length and seedling weight were more important with respect to the other growth parameters.     

Remote sensing to detect plant stress induced by Heterodera schachtii and Rhizoctonia solani in sugar beet fields

The characteristically clustered occurrence and low level of mobility of Heterodera schachtii and Rhizoctonia solani in the soil and the induction of stress symptoms in the sugar beet canopy make them ideal targets for site-specific arrangements with precision agriculture tools. A field site infested with H. schachtii and R. solani was investigated in 2009 with near-range and aerial hyperspectral sensors during the growing season. At 31 sample points ground truth data for incidence and severity of the two organisms were collected and geo-referenced. Spectral vegetation indices computed from reflectance measurements obtained from two flight campaigns (AISA, 17th of June; HyMap, 28th of August) and the near-range spectroradiometers were significantly correlated (P < 0.01) with symptoms caused by the nematode or Rhizoctonia crown and root rot. A supervised classification with Spectral Angle Mapper of leaf symptoms induced by the organisms resulted in a classification accuracy of 72 and 64% for the AISA and HyMap data, respectively. The results demonstrated that remote sensing in combination with geographic information system technologies can be used effectively for the detection and mapping of symptoms caused by beet cyst nematode and Rhizoctonia crown and root rot.