Modification of the RLA model for presenting a cluster system of a composite material with a fractal filler structure

The paper proposes a modification of the diffusion-limited aggregation model to study the properties of a cluster system. A computational experiment to determine the mutual influence of the sticking probability and the volume concentration of particles on the formation of fractal clusters in a cluster system was carried out in accordance  with  the  second-order  orthogonal  central  compositional  plan  (OCCP).  As  a  result of a computational experiment in accordance with the OCCP, an equation was obtained for the dependence of the mass fractal dimension of clusters on the volume of particle concentration and the probability of adhesion of diffusing particles and cluster particles in the adhesion zone. This dependence was obtained in a range of volume concentration of particles from 2 to 5 % and the probability of adhesion of diffusing particles and particles of clusters in the adhesion zone from 0.2 to 1.The paper proposes a modification of the diffusion-limited aggregation model to study the properties of a cluster system. A computational experiment to determine the mutual influence of the sticking probability and the volume concentration of particles on the formation of fractal clusters in a cluster system was carried out in accordance  with  the  second-order  orthogonal  central  compositional  plan  (OCCP).  As  a  result of a computational experiment in accordance with the OCCP, an equation was obtained for the dependence of the mass fractal dimension of clusters on the volume of particle concentration and the probability of adhesion of diffusing particles and cluster particles in the adhesion zone. This dependence was obtained in a range of volume concentration of particles from 2 to 5 % and the probability of adhesion of diffusing particles and particles of clusters in the adhesion zone from 0.2 to 1

Evaluation of cowpea mini core accessions for resistance to flower bud thrips Megalurothrips sjostedti Trybom (Thysanoptera: Thripidae)

Open Access ArticleThe flower bud thrips, Megalurothrips sjostedti Trybom (Thysanoptera: Thripidae), is an economically important pest of cowpea in sub‐Saharan Africa. Varietal resistance is the most preferred, environmentally friendly, cost‐effective and sustainable option for controlling this pest. The objective of this study was to identify sources of resistance to M. sjostedti among mini core accessions from the largest world cowpea germplasm collection maintained at the International Institute of Tropical Agriculture (IITA). The study was conducted during the 2015 and 2016 cropping seasons where 365 accessions were screened under field conditions. Each accession was rated visually for thrips damage score, flower abortion rate, number of pods per plant and number of thrips per flower. The resistance levels observed in genotypes TVu8631, TVu16368, TVu8671 and TVu7325 were similar to that of the resistant check “Sanzisabinli” (called Sanzi) during both seasons. In addition, 56 mini core genotypes showed moderate resistance to thrips damage. High heritability values were associated with thrips damage scores at 65 days after planting (0.60), percentage of effective peduncles (0.59), flower bud abortion rate (0.59), number of pods per plant (0.51) and number of peduncles with pods (0.5). The accessions identified with good levels of resistance to flower bud thrips will be used in cowpea breeding programs to develop improved resistant varieties

Global warming induced hybrid rainy seasons in the Sahel

Open Access JournalThe small rainfall recovery observed over the Sahel, concomitant with a regional climate warming, conceals some drought features that exacerbate food security. The new rainfall features include false start and early cessation of rainy seasons, increased frequency of intense daily rainfall, increasing number of hot nights and warm days and a decreasing trend in diurnal temperature range. Here, we explain these mixed dry/wet seasonal rainfall features which are called hybrid rainy seasons by delving into observed data consensus on the reduction in rainfall amount, its spatial coverage, timing and erratic distribution of events, and other atmospheric variables crucial in agro-climatic monitoring and seasonal forecasting. Further composite investigations of seasonal droughts, oceans warming and the regional atmospheric circulation nexus reveal that the low-to-mid-level atmospheric winds pattern, often stationary relative to either strong or neutral El-Niño-Southern-Oscillations drought patterns, associates to basin warmings in the North Atlantic and the Mediterranean Sea to trigger hybrid rainy seasons in the Sahel. More challenging to rain-fed farming systems, our results suggest that these new rainfall conditions will most likely be sustained by global warming, reshaping thereby our understanding of food insecurity in this region

Lower soil moisture threshold for transpiration decline under water deficit correlates with lower canopy conductance and higher transpiration efficiency in drought-tolerant cowpea

As water availability is critical for reproduction, terminal drought tolerance may involve water-saving traits. Experiments were undertaken under different vapour pressure deficit (VPD) and water regimes (water stress (WS) and well watered (WW)) to test genotypic differences and trait relationships in the fraction of transpirable soil water (FTSW) at which transpiration declines, canopy conductance (proxied by transpiration rate (TR, g H2O cm–2 h–1)), canopy temperature depression (CTD, °C), transpiration efficiency (TE, g kg–1) and growth parameters, using 15 contrasting cowpea (Vigna unguiculata (L.) Walp.) genotypes. Under WW conditions at the vegetative and early podding stages, plant mass and leaf area were larger under low VPD, and was generally lower in tolerant than in sensitive genotypes. Several tolerant lines had lower TR under WW conditions and restricted TR more than sensitive lines under high VPD. Under WS conditions, transpiration declined at a lower FTSW in tolerant than in sensitive lines. Tolerant lines also maintained higher TR and CTD under severe stress. TE was higher in tolerant genotypes under WS conditions. Significant relationships were found between TR, and TE, CTD and FTSW under different water regimes. In summary, traits that condition how genotypes manage limited water resources discriminated between tolerant and sensitive lines. Arguably, a lower canopy conductance limits plant growth and plant water use, and allows tolerant lines to behave like unstressed plants until the soil is drier and to maintain a higher TR under severe stress, as lower TR at high VPD leads to higher TE

Modification of the RLA model for presenting a cluster system of a composite material with a fractal filler structure

The paper proposes a modification of the diffusion-limited aggregation model to study the properties of a cluster system. A computational experiment to determine the mutual influence of the sticking probability and the volume concentration of particles on the formation of fractal clusters in a cluster system was carried out in accordance with the second-order orthogonal central compositional plan (OCCP). As a result of a computational experiment in accordance with the OCCP, an equation was obtained for the dependence of the mass fractal dimension of clusters on the volume of particle concentration and the probability of adhesion of diffusing particles and cluster particles in the adhesion zone. This dependence was obtained in a range of volume concentration of particles from 2 to 5 % and the probability of adhesion of diffusing particles and particles of clusters in the adhesion zone from 0.2 to 1

Characterization of pearl millet root architecture and anatomy reveals three types of lateral roots

Pearl millet plays an important role for food security in arid regions of Africa and India. Nevertheless, it is considered an orphan crop as it lags far behind other cereals in terms of genetic improvement efforts. Breeding pearl millet varieties with improved root traits promises to deliver benefits in water and nutrient acquisition. Here, we characterize of early pearl millet root system development using several different root phenotyping approaches that include rhizotrons and microCT. We report that early stage pearl millet root system development is characterized by a fast growing primary root that quickly colonizes deeper soil horizons. We also describe root anatomical studies that revealed 3 distinct types of lateral roots that form on both primary roots and crown roots. Finally, we detected significant variation for two root architectural traits in pearl millet inbred lines. This study provides the basis for subsequent genetic experiments to identify loci associated with interesting early root development traits in this important cereal

Cowpea (Vigna unguiculata): Genetics, genomics and breeding

Article purchased; Published online: 9 May 2018Cowpea, Vigna unguiculata (L.), is an important grain legume grown in the tropics where it constitutes a valuable source of protein in the diets of millions of people. Some abiotic and biotic stresses adversely affect its productivity. A review of the genetics, genomics and breeding of cowpea is presented in this article. Cowpea breeding programmes have studied intensively qualitative and quantitative genetics of the crop to better enhance its improvement. A number of initiatives including Tropical Legumes projects have contributed to the development of cowpea genomic resources. Recent progress in the development of consensus genetic map containing 37,372 SNPs mapped to 3,280 bins will strengthen cowpea trait discovery pipeline. Several informative markers associated with quantitative trait loci (QTL) related to desirable attributes of cowpea were generated. Cowpea genetic improvement activities aim at the development of drought tolerant, phosphorus use efficient, bacterial blight and virus resistant lines through exploiting available genetic resources as well as deployment of modern breeding tools that will enhance genetic gain when grown by sub‐Saharan Africa farmers

Rhizobium inoculants suppress emergence of the weed Striga gesnerioides in cowpea

Open Access Article; Published online: 26 May 2021Cowpea is a grain legume of major importance in sub-Saharan Africa where it is cultivated by smallholder farmers on poor soils and production is often constrained by the parasitic weed Striga gesnerioides. Experiments were conducted to assess the potential of rhizobium inoculation in mitigating Striga infestation and increasing cowpea productivity. We tested under basal P application and artificial S. gesnerioides inoculation the impact of cowpea genotypes (G) (nine Striga-resistant and 11 Striga– susceptible genotypes) and bradyrhizobium inoculation (N) (two bradyrhizobium strains USDA3384 and IRJ2180A, and uninoculated control) on Striga dynamics and cowpea yield. Additional treatments included N supplied as urea (with and without), and no input (i.e., soil inherent N and P) that served as negative check. A first experiment was carried out in potted sterile soils in the screen house excluding addition of N-fertilizers. Significant G x N interactions were observed in counts of nodule (P = 0.012), Striga attachment (P < 0.0001) and emergence (P = 0.005), and cowpea shoot growth (P = 0.016). Cowpea nodulated poorly across host lines, Striga counts were the lowest for resistant varieties with no emerged plants. Rhizobial inoculants depressed Striga counts with consistent differences found across cowpea genotypes. Inoculation with IRJ2180A performed the best against Striga attachment in resistant genotypes, and its emergence in susceptible genotypes. In the field trial, nodule numbers were lowest in cowpea without inputs (P < 0.0001). The G x N interaction was significant in emerged Striga plants (P < 0.0001). Resistant genotypes were free of emerged Striga while for susceptible ones, Striga emergence was the highest without any input addition. Significant G x N interaction was observed in cowpea grain yield (P < 0.0001). Yield response to inoculation was most obvious for resistant genotypes inoculated with the strain IRJ2180A (P = 0.0043). The integrated use of Striga-resistant cowpea lines and elite bradyrhizobium inoculant under moderate application of P-based fertilizer could be a promising approach for mitigating Striga infestation and increasing productivity

ОПТИЧЕСКИЕ СВОЙСТВА КОМПЛЕКСОВ УЛЬТРАДИСПЕРСНЫХ АЛМАЗОВ ДЕТОНАЦИОННОГО СИНТЕЗА С ИНДОТРИКАРБОЦИАНИНОВЫМ КРАСИТЕЛЕМ

A method to create complexes of detonation nanodiamonds with molecules of an indotricarbocyanine dye was developed. The process of complex formation was shown to depend on the nanodiamond annealing conditions. Nanodiamonds that were vacuum annealed at 750oC display the most effective interaction with the dye molecules. Formation of the complexes was studied with the aid of optical spectroscopy in the visible and infrared regions.Разработан метод получения комплексов ультрадисперсных алмазов детонационного синтеза с молекулами индотрикарбоцианинового красителя. Показано, что на процесс комплексообразования влияют условия термической обработки наноалмазов. Наиболее эффективное взаимодействие с красителем проявляется для ультрадисперсных алмазов, отожженных в вакууме при 750оС. Процесс образования комплексов изучен методом оптической спектроскопии в видимой и инфракрасной областях