VARIABILITY OF VOLATILE ORGANIC COMPOUNDS EMITTED BY SEEDLINGS OF SEVEN AFRICAN MAIZE VARIETIES WHEN INFESTED BY ADULT CICADULINA STOREYI CHINA LEAFHOPPER VECTORS OF MAIZE STREAK VIRUS

Maize ( Zea mays L.) is an important source of energy for the people in sub-Saharan Africa. Unfortunately, maize production is under the threat of Maize streak virus (MSV) (Geminiviridae: genus Mastrevirus), an endemic pathogen of native African grasses. This virus is acquired and transmitted in a persistent manner, by Cicadulina spp. leafhoppers (Homoptera: Cicadellidae) .One possibility for controlling the virus and the vectors is to exploit volatile semiochemicals released by plants following insect herbivory. A study was conducted on herbivoreinduced volatile organic compounds (VOCs) of seven African maize (Zea mays L.) varieties in the presence of the leafhopper ( Cicadulina storeyi China, Homoptera: Cicadellidae) an important vector of maize streak virus (MSV) with a view of developing novel leafhopper control strategies in sub-Saharan Africa. VOCs are known to repel herbivory and also serve as cues for parasitoids to locate their hosts. Volatiles were collected from young maize seedlings of 7 varieties after entrainment with or without infestation of leafhoppers in 0 - 24, 24 - 48, 48 - 72 and 72\u201396 hr periods and combined and subsequently analysed by gas chromatography. Analysis of the VOCs collected from the seven elite African varieties shows high interspecific VOC variability. Gas chromatography (GC) and coupled GC-mass spectrometry (GC-MS) led to the identification of (z)-3-hexen-1-ol, heptanal, (z)- 2-pentenyl acetate, MHO, octanal, myrcene, (z)-3-hexen-1-yl acetatate, (E)-3-hexen-1-yl acetatate, nonanal Linalool, DMNT, (E)-2-decen-1-ol, Methyl salicylate, DMNT, Phenethyl acetate, Indole, cis-jasmone, \u3b1- copaene, Geranyl acetone, \u3b2-caryophyllene, \u3b1-bergamotene, (E)-\u3b2-farnesens, TMTT, and Humulene from infested seedlings. Of these, methyl salicylate, (E)-caryophyllene, (E)-\u3b2-farnesene and TMTT were identified previously as volatile semiochemicals involved in plant defense against other sucking insect pests. TZB-SR seedlings emitted 22 compounds in the presence of leafhoppers, compared with 5 by uninfested seedlings; while BR9943-DMR.SR emitted only seven compound in the presence of leafhoppers compared with 6 by uninfested seedlings. The compounds emitted by the seven maize varieties after herbivory were in the following descending order: TZB-SR > TZBR.ELD3.C3 > AMA.TZBR = 8338-1> GUSAU 81.POOL16-SR = 9021-18.STR > BR9943-DMR.SR. Although these varieties were bred for resistance to MSV and other production constraints like downy mildew and stem borers, the variability being reported would have significant ecological implications in utilising plant induced volatiles as repellents for leafhoppers in controlling MSV and underscores the need to breed for varieties that produce volatiles which are very attractive to biological control agents and repellent to leafhoppers. This is the first report of variability of maize genotypes on herbivores-induced volatiles from an African pest/pathogen complex and is in conformity with previous studies that maize shows relatively high genetic and VOC variability, both intrinsically and in herbivore-induced emissions.Le ma\uefs ( Zea mays L.) est une importante source d\u2019\ue9nergie du peuple d\u2019Afrique sub-saharienne. Malheureusement, sa production est affect\ue9e par la striure brune du ma\uefs (MSV) (Geminiviridae: genus Mastrevirus), un pathog\ue8ne end\ue9mique originaire d\u2019herbes africaines. Ce virus est acquis et transmis de mani\ue8re persistante par la Cicadelle (Homoptera: Cicadellidae). Pour contr\uf4ler ce virus et ses vecteurs, il est possible d\u2019exploiter les produits semiochimiques \ue9mis par les plantes infest\ue9es par les insects. Une \ue9tude \ue9tait effectu\ue9e sur des compos\ue9s organiques volatiles \ue9mis par sept vari\ue9t\ue9s de ma\uefs (Zea mays L.) losrqu\u2019infect\ue9es par la cicadelle ( Cicadulina storeyi China, Homoptera: Cicadellidae), un vecteur important du virus de la striure de ma\uefs (MSV) afin de d\ue9velopper des strat\ue9gies de contr\uf4l de la cicadelle en Afrique sub-saharienne. Les VOCs servent comme signaux pour les parasito\uefdes afin de localiser leurs h\uf4tes. Les volatiles \ue9taient collect\ue9s des jeunes plants des sept vari\ue9t\ue9s apr\ue8s introduction ou pas d\u2019infestation de la cicadelle \ue0 des p\ue9riodes de temps allant de 0 - 24, 24 - 48, 48 - 72 and 72\u201396 heures et combin\ue9e, plutard analys\ue9s \ue0 l\u2019aide du gaz chromatographique. L\u2019analyse des VOCs issus de sept vari\ue9t\ue9s africaines \ue9lites montre une variabilit\ue9 intersp\ue9cifique des VOCs. Le gaz chromatographique (GC) et la combinaison GC- masse sp\ue9ctrom\ue9trie (GC-MS) ont permis l\u2019identification de (z)-3-hexen-1-ol, heptanal, (z)-2-pentenyl acetate, MHO, octanal, myrcene, (z)-3-hexen-1-yl acetatate, (E)-3-hexen-1-yl acetatate, nonanal Linalool, DMNT, (E)-2-decen-1-ol, Methyl salicylate, DMNT, Phenethyl acetate, Indole, cisjasmone, \u3b1-copaene, Geranyl acetone, \u3b2-caryophyllene, \u3b1-bergamotene, (E)-\u3b2-farnesens, TMTT, et Humulene dans des plants infest\ue9es. De tous ces produits pr\ue9cit\ue9s, seuls methyl salicylate, (E)-caryophyllene, (E)-\u3b2- farnesene et TMTT \ue9taient auparavant identifi\ue9s comme volatiles semiochemiques impliqu\ue9s dans la d\ue9fence des plants contre d\u2019autres pestes d\u2019insectes suceurs des plantes. Les plants TZB-SR ont \ue9mis 22 compos\ue9s en pr\ue9sence de la cicadelle en comparaison avec 5 plants non infest\ue9s; alors que BR9943-DMR.SR ont \ue9mis seulement sept compos\ue9s en pr\ue9sence de la cicadelle en comparaison de 6 plants non infest\ue9s. Les compos\ue9s \ue9mis par les sept vari\ue9t\ue9s de ma\ubfs apr\ue8s infestation de la cicadelle \ue9taient classes comme suit par ordre descendant: TZB-SR > TZBR.ELD3.C3 >AMA.TZBR = 8338-1> GUSAU 81.POOL16-SR = 9021-18.STR > BR9943- DMR.SR. Bien que ces vari\ue9t\ue9s \ue9taient dot\ue9es de r\ue9sistance au MSV et autres contraintes \ue0 la production comme le mildew et le stem borers, la variabilit\ue9 manifest\ue9e pourrait avoir des implications \ue9cologiques significatives dans l\u2019utilisation des compos\ue9s volatiles \ue9mis des plantes comme moyen de repousser les cicadelles dans le contr\uf4l du MSV. Ceci souligne le besoin d\u2019entreprendre des \ue9tudes d\u2019am\ue9lioration g\ue9n\ue9tique des vari\ue9t\ue9s pouvant \ue9mettre des compos\ue9s volatiles comme agent de contr\uf4l biologique et repulsif de la cicadelle. Ceci constitue le premier rapport sur la variabilit\ue9 des g\ue9notypes de ma\ubfs eu \ue9gard aux compos\ue9s volatiles organiques \ue9mis \ue0 partir du complexe de peste/pathog\ue8ne africain. Ceci est en conformit\ue9 avec des \ue9tudes ant\ue9rieures qui montrent une relative variabilit\ue9 g\ue9n\ue9tique et des VOCs, tous intrins\ue9quement dans des \ue9missions induites des herbivores

Gender appropriateness of field days in knowledge generation and adoption of push-pull technology in eastern Africa

Adoption studies have identified gender as one of the factors that determine technology uptake and this has been linked to women’s access to farming information or lack of it. Technology scaling up systems should utilise pathways that are compatible with the needs of rural women, who have to juggle farming with other household chores. Unfortunately, there has been limited effort to evaluate the suitability of the information pathways used to specific gender. The current study evaluates the appropriateness of field days with respect to gender of the participants. Data were collected from selected farmers who attended field days in Kenya, Uganda and Tanzania in 2014. A total of 2 615 participants were interviewed out of 6 221 who attended field days. Descriptive analysis and ordered probit and logit models were used for analysis. The majority of the participants in Kenya and Tanzania were women (51.3% and 62.6%, respectively), whereas in Uganda the majority of participants were men (57.4%). Most participants were middle aged (42 years for women and 45 years for men). The majority of the women (54.1%) had primary level education, with only 29.1% having secondary education, whereas 41% and 40.1% of men had attained primary and secondary education, respectively. The results from the econometric models shows that gender, age, education, being push-pull farmers, perceptions on Striga severity were the main significant determinants of knowledge for the ordered probit. Conversely, gender of the participant, perception on stemborers and Striga weed severity and having mobile phones were the significant determinants of willingness to adopt. The two models were significant at 1% (p < 0.001). The significance of the gender variable in the two models shows that women farmers understood more about push-pull (coefficient of ordered probit = −0.112) when trained during field days. Furthermore, the willingness to adopt push-pull after the training was much higher for women (coefficient of logit = −0.367) compared with men. The findings demonstrate that field days can be more appropriate for training farmers, especially women who are often disadvantaged in information access, as a result of their socio-economic circumstances

Palaeontology, the biogeohistory of Victoria

The broad-scale distribution of fossils within Victoria is controlled by general global patterns in the biological evolution of life on Earth, the local development and environmental evolution of habitats, and the occurrence of geological processes conducive to the preservation of fossil floras and faunas. Early Palaeozoic fossils are mostly marine in origin because of the predominance of marine sedimentary rocks in Victoria and because life on land was not significant during most of this time interval. Middle Palaeozoic sequences have both terrestrial and marine fossil records. Within Victoria, marine rocks are only very minor components of strata deposited during the late Palaeozoic, so that few marine fossils are known from this time period. A similar situation existed during most of the Mesozoic except towards the end of this era when marine conditions began to prevail in the Bass Strait region. During long intervals in the Cainozoic, large areas of Victoria were flooded by shallow-marine seas, particularly in the southern basins of Bass Strait, as well as in the northwest of the State (Murray Basin). Cainozoic sediments contain an extraordinary range of animal and plant fossils. During the Quaternary, the landscape of Victoria became, and continues to be, dominated by continental environments including, at times, extensive freshwater lake systems. Fossil floras and faunas from sediments deposited in these lake systems and from other continental sediments, as well as from Quaternary sediments deposited in marginal marine environments, collectively record a history of rapid fluctuations in climate and sea level.<br /

Disordered Bosons: Condensate and Excitations

The disordered Bose Hubbard model is studied numerically within the Bogoliubov approximation. First, the spatially varying condensate wavefunction in the presence of disorder is found by solving a nonlinear Schrodinger equation. Using the Bogoliubov approximation to find the excitations above this condensate, we calculate the condensate fraction, superfluid density, and density of states for a two-dimensional disordered system. These results are compared with experiments done with ${}^4{\rm He}$ adsorbed in porous media.Comment: RevTeX, 26 pages and 10 postscript figures appended (Figure 9 has three separate plots, so 12 postcript files altogether

Blinded Predictions and Post Hoc Analysis of the Second Solubility Challenge Data: Exploring Training Data and Feature Set Selection for Machine and Deep Learning Models

Accurate methods to predict solubility from molecular structure are highly sought after in the chemical sciences. To assess the state of the art, the American Chemical Society organized a "Second Solubility Challenge"in 2019, in which competitors were invited to submit blinded predictions of the solubilities of 132 drug-like molecules. In the first part of this article, we describe the development of two models that were submitted to the Blind Challenge in 2019 but which have not previously been reported. These models were based on computationally inexpensive molecular descriptors and traditional machine learning algorithms and were trained on a relatively small data set of 300 molecules. In the second part of the article, to test the hypothesis that predictions would improve with more advanced algorithms and higher volumes of training data, we compare these original predictions with those made after the deadline using deep learning models trained on larger solubility data sets consisting of 2999 and 5697 molecules. The results show that there are several algorithms that are able to obtain near state-of-the-art performance on the solubility challenge data sets, with the best model, a graph convolutional neural network, resulting in an RMSE of 0.86 log units. Critical analysis of the models reveals systematic differences between the performance of models using certain feature sets and training data sets. The results suggest that careful selection of high quality training data from relevant regions of chemical space is critical for prediction accuracy but that other methodological issues remain problematic for machine learning solubility models, such as the difficulty in modeling complex chemical spaces from sparse training data sets

Genome-wide association analysis of a stemborer egg induced “call‑for‑help” defence trait in maize

Published online: 08 Jul 2020Tritrophic interactions allow plants to recruit natural enemies for protection against herbivory. Here we investigated genetic variability in induced responses to stemborer egg-laying in maize Zea mays (L.) (Poaceae). We conducted a genome wide association study (GWAS) of 146 maize genotypes comprising of landraces, inbred lines and commercial hybrids. Plants were phenotyped in bioassays measuring parasitic wasp Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae) attraction to volatiles collected from plants exposed to stemborer Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) eggs. Genotyping-by-sequencing was used to generate maize germplasm SNP data for GWAS. The egg-induced parasitoid attraction trait was more common in landraces than in improved inbred lines and hybrids. GWAS identified 101 marker-trait associations (MTAs), some of which were adjacent to genes involved in the JA-defence pathway (opr7, aos1, 2, 3), terpene biosynthesis (fps3, tps2, 3, 4, 5, 7, 9, 10), benzoxazinone synthesis (bx7, 9) and known resistance genes (e.g. maize insect resistance 1, mir1). Intriguingly, there was also association with a transmembrane protein kinase that may function as a receptor for the egg elicitor and other genes implicated in early plant defence signalling. We report maize genomic regions associated with indirect defence and provide a valuable resource for future studies of tritrophic interactions in maize. The markers identified may facilitate selection of indirect defence by maize breeders

Ultrasound attenuation in gap-anisotropic systems

Transverse ultrasound attenuation provides a weakly-coupled probe of momentum current correlations in electronic systems. We develop a simple theory for the interpretation of transverse ultrasound attenuation coefficients in systems with nodal gap anisotropy. Applying this theory we show how ultrasound can delineate between extended-s and d-wave scenarios for the cuprate superconductors.Comment: Uuencode file: 4 pages (Revtex), 3 figures. Some references adde

Signal Grass (Brachiaria brizantha) Oviposited by Stemborer (Chilo partellus) Emits Herbivore-Induced Plant Volatiles That Induce Neighbouring Local Maize (Zea mays) Varieties to Recruit Cereal Stemborer Larval Parasitoid Cotessia sesamiae

Plants respond to attack by herbivores with the release of herbivore-induced plant volatiles (HIPVs). In return, natural enemies (predators and parasitoids) respond to these emitted herbivore-induced plant volatiles while foraging for their hosts. Neighboring plants of the same family may be induced by the emitted HIPVs. This is a tritrophic interaction that leads to a