Chitin in Strawberry Cultivation: Foliar Growth and Defense Response Promotion, but Reduced Fruit Yield and Disease Resistance by Nutrient Imbalances.

Strawberry cultivation is associated with high mineral fertilizer doses and extensive use of chemical plant protection products. Based on previous research, we expected that chitin application to peat substrate would increase the nutrient availability and activate the plant systemic defense response, resulting in higher strawberry yields and fewer disease symptoms. We set up two experiments in which the temporal variability and differences in initial nutrient concentrations of the growing media were taken into account. Chitin treatment resulted in the attraction of plant growth-promoting fungi toward the plant root, such as species from genera Mortierella and Umbelopsis. In addition, by the end of the experiments 87 mg of mineral nitrogen (N) per liter of substrate was mineralized, which can be related to the observed increase in plant shoot biomass. This, however, led to nutrient imbalances in plant shoots and fruit; N concentration in the leaves increased over 30%, exceeding the optimal range, while phosphorous (P) and potassium (K) deficiencies occurred, with concentrations lower than 50% of the optimal range. This may explain the decreased fruit yield and disease resistance of the fruit toward Botrytis cinerea. In contrast, chitin caused a clear defense priming effect in the strawberry leaves, with a strong induction of the jasmonic acid response, resulting in fewer foliar disease symptoms. Chitin causes positive effects on shoot growth and foliar disease resistance, but caution needs to be taken for nutrient imbalances leading to negative influences on root growth, fruit production, and disease susceptibility toward B. cinerea.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Comparing systemic defence-related gene expression changes upon migratory and sedentary nematode attack in rice.

Complex defence signalling pathways, controlled by different hormones, are known to be involved in the reaction of plants to a wide range of biotic and abiotic stress factors. Here, we studied the differential expression of genes involved in stress and defence responses in systemic tissue of rice infected with the root knot nematode (RKN) Meloidogyne graminicola and the migratory root rot nematode Hirschmanniella oryzae, two agronomically important rice pathogens with very different lifestyles. qRT-PCR revealed that all investigated systemic tissues had significantly lower expression of isochorismate synthase, a key enzyme for salicylic acid production involved in basal defence and systemic acquired resistance. The systemic defence response upon migratory nematode infection was remarkably similar to fungal rice blast infection. Almost all investigated defence-related genes were up-regulated in rice shoots 3 days after root rot nematode attack, including the phenylpropanoid pathway, ethylene pathway and PR genes, but many of which were suppressed at 7 dpi. Systemic shoot tissue of RKN-infected plants showed similar attenuation of expression of almost all studied genes already at 3 dpi, with clear attenuation of the ethylene pathway and methyl jasmonate biosynthesis. These results provide an interesting starting point for further studies to elucidate how nematodes are able to suppress systemic plant defence mechanisms and the effect in multitrophic interactions.

Cross-species microsatellite amplification in Vasconcellea and related genera and their use in germplasm classification.

To generate inexpensive and efficient DNA markers for addressing a number of population genetics problems and identification of wild hybrids in Vasconcellea, we have evaluated the use of simple sequence repeat (SSR) primers previously developed for other species. A set of 103 Vasconcellea accessions and some individuals of the related genera Carica and Jacaratia were analyzed with 10 primer pairs directing amplification of chloroplast microsatellites in Nicotiana tabacum and 9 nuclear SSR primer pairs recently identified in Vasconcellea x heilbornii. Heterologous amplification of chloroplast SSRs was successful for 8 of the 10 loci, of which 6 showed polymorphism. Seven of the 9 nuclear SSR primer pairs were useful in Vasconcellea and often also in Jacaratia and Carica, all revealing polymorphism. Exclusive haplotypes for each described taxon were identified based on chloroplast microsatellite data. Clustering based on separate nuclear and chloroplast data resulted in a clear grouping per taxon, but only low resolution was obtained above species level. The codominancy of nuclear SSRs and the general high polymorphism rate of SSR markers will make them more useful in future population genetics studies and diversity assessment in conservation programs.

Patterns of genetic and morphometric diversity in baobab (Adansonia digitata) populations across different climatic zones of Benin (West Africa).

BACKGROUND AND AIMS: Baobab (Adansonia digitata) is a multi-purpose tree used daily by rural African communities. The present study aimed at investigating the level of morphometric and genetic variation and spatial genetic structure within and between threatened baobab populations from the three climatic zones of Benin. METHODS: A total of 137 individuals from six populations were analysed using morphometric data as well as molecular marker data generated using the AFLP technique. KEY RESULTS: Five primer pairs resulted in a total of 217 scored bands with 78.34 % of them being polymorphic. A two-level AMOVA of 137 individuals from six baobab populations revealed 82.37 % of the total variation within populations and 17.63 % among populations (P < 0.001). Analysis of population structure with allele-frequency based F-statistics revealed a global F(ST) of 0.127 +/- 0.072 (P < 0.001). The mean gene diversity within populations (H(S)) and the average gene diversity between populations (D(ST)) were estimated at 0.309 +/- 0.000 and 0.045 +/- 0.072, respectively. Baobabs in the Sudanian and Sudan-Guinean zones of Benin were short and produced the highest yields of pulp, seeds and kernels, in contrast to the ones in the Guinean zone, which were tall and produced only a small number of fruits with a low pulp, seed and kernel productivity. A statistically significant correlation with the observed patterns of genetic diversity was observed for three morphological characteristics: height of the trees, number of branches and thickness of the capsules. CONCLUSIONS: The results indicate some degree of physical isolation of the populations collected in the different climatic zones and suggest a substantial amount of genetic structuring between the analysed populations of baobab. Sampling options of the natural populations are suggested for in or ex situ conservation.

Evidence of natural hybridization and introgression between Vasconcellea species (Caricaceae) from southern Ecuador revealed by chloroplast, mitochondrial and nuclear DNA markers.

BACKGROUND AND AIMS: Vasconcellea x heilbornii is believed to be of natural hybrid origin between V. cundinamarcensis and V. stipulata, and is often difficult to discriminate from V. stipulata on morphological grounds. The aim of this paper is to examine individuals of these three taxa and of individuals from the closely related species V. parviflora and V. weberbaueri, which all inhabit a hybrid zone in southern Ecuador. METHODS: Molecular data from mitochondrial, chloroplast and nuclear DNA from 61 individuals were analysed. KEY RESULTS: Molecular analysis confirmed occasional contemporary hybridization between V. stipulata, V. cundinamarcensis and V. x heilbornii and suggested the possible involvement of V. weberbaueri in the origin of V. x heilbornii. In addition, the molecular data indicated unidirectional introgression of the V. cundinamarcensis nuclear genome into that of V. stipulata. Several of the individuals examined with morphology similar to that of V. stipulata had genetic traces of hybridization with V. cundinamarcensis, which only seems to act as pollen donor in interspecific hybridization events. Molecular analyses also strongly suggested that most of the V. x heilbornii individuals are not F(1) hybrids but instead are progeny of repeated backcrosses with V. stipulata. CONCLUSIONS: The results of the present study point to the need for re-evaluation of natural populations of V. stipulata and V. x heilbornii. In general, this analysis demonstrates the complex patterns of genetic and morphological diversity found in natural plant hybrid zones.

Phylogenetic analysis of the highland papayas ( Vasconcellea) and allied genera (Caricaceae) using PCR-RFLP.

The chloroplast and mitochondrial DNA diversity of 61 genotypes belonging to 18 Vasconcellea species, the so-called highland papayas, was studied by PCR-RFLP analysis of two non-coding cpDNA regions ( trnM- rbcL and trnK1- trnK2) and one non-coding mtDNA region ( nad4/1- nad4/2). This sample set was supplemented with six genotypes belonging to three other Caricaceae genera: the monotypic genus Carica, including only the cultivated papaya, and the genera Jacaratia and Cylicomorpha. Moringa ovalifolia was added as an outgroup species. The PCR-amplified cpDNA regions were digested with 18 restriction endonucleases, the mtDNA region with 11. A total of 22 point mutations and four insertion/deletions were scored in the sample. A higher level of interspecific variation was detected in the two cpDNA regions in comparison to the analysis of the mtDNA. Wagner parsimony and Neighbor-Joining analysis resulted in dendrograms with similar topologies. PCR-RFLP analysis supported the monophyly of Caricaceae, but among the 26 mutations scored, an insufficient number of markers discriminated between the different Caricaceae genera included in this study. Hence the inference of the intergeneric relationships within Caricaceae was impossible. However, some conclusions can be noted at a lower taxonomic level. The Caricaceae species were divided into two lineages. One group included only Vasconcellea spp., whereas the second included the remaining Vasconcellea spp., together with the papaya genotypes and those from the other Caricaceae genera. This may indicate a higher level of inter-fertility for the Vasconcellea species from the latter clade in interspecific crossings with papaya. The putative progenitors of the natural sterile hybrid V. x heilbornii, i.e. V. stipulata and V. cundinamarcensis, were only distantly related to V. x heilbornii. This indicates that probably none of these species was involved as the maternal progenitor in the origin of V. x heilbornii. Surprisingly, V. x heilbornii had organellar genome patterns identical with V. weberbaueri, suggesting a possible involvement of this species in the origin of V. x heilbornii. On the basis of discrepancy between morphological traits and the cpDNA profiles of some pairs of Vasconcellea species, we believe that besides V. x heilbornii, some other species have originated through interspecific hybridization. A reticulate evolution for Vasconcellea has therefore been suggested. Finally, intraspecific cpDNA variation was detected in V. microcarpa, thus providing molecular evidence for the high diversity previously indicated by morphological observations.

AFLP analysis of genetic relationships among papaya and its wild relatives (Caricaceae) from Ecuador.

The AFLP technique was used to assess the genetic relationships among the cultivated papaya ( Carica papaya L.) and related species native to Ecuador. Genetic distances based on AFLP data were estimated for 95 accessions belonging to three genera including C. papaya, at least eight Vasconcella species and two Jacaratia species. Cluster analysis using different methods and principal co-ordinate analysis (PCO), based on the AFLP data from 496 polymorphic bands generated with five primer combinations, was performed. The resulted grouping of accessions of each species corresponds largely with their taxonomic classifications and were found to be consistent with other studies based on RAPD, isozyme and cpDNA data. The AFLP analysis supports the recent rehabilitation of the Vasconcella group as a genus; until recently Vasconcella was considered as a section within the genus Carica. Both cluster and PCO analysis clearly separated the species of the three genera and illustrated the large genetic distance between C. papaya accessions and the Vasconcella group. The specific clustering of the highly diverse group of Vasconcella x heilbornii accessions also suggests that these genotypes may be the result of bi-directional introgression events between Vasconcella stipulata and Vasconcella cundinamarcensis.

[The intervertebral disk. Attempt at a "finite element" model]. / Le disque intervertébral. Tentative de modélisation en "éléments finis".

Intervertebral disk composite model is unsatisfactory definite in biomechanical behaviour despite multiples technics used. Using histologic and histoenzymology it's possible to determinate proportions of collagen fibers in the different parts of the disk. A trustworthy finite element 3D model is proposed and tried by real experiments.

A model of the human lumbar vertebral column: a preliminary study.

Finite element modelling of the human lumbar vertebral column employs data-processing procedures for study of the linear and nonlinear elasticity of materials such as are currently used in mechanics or in civil engineering. Thanks to developments in computer science, requiring a close collaboration between doctors and engineers, we put forward in this preliminary study a linear computerised model of the lumbar column comprising 4824 meshes and 6813 nodes. By reducing the simplificatory hypotheses and integrating new parameters, this model as developed is capable of important clinical applications in surgery and ergonomics.

Preliminary study of the human lumbar spine using speckle technique. Limits of compression, shear and torsion. Speckle photography--electronic speckle pattern interferometry.

Optical techniques using single wavelength lasers allow precise study of the superficial displacements of deeper anatomical structures through direct mechanical pull. Two techniques have been used in this study: 1. Double exposure speckle photography. Since 1980 the relationship between the surface displacements and minimal traction applied to the transverse processes of the spine, either unilateral or bilateral, was studied in an attempt to simulate muscular action exerted at this level. 2. Computerised speckle interferometry. This allowed analysis of the deformations between the lumbar vertebrae under vertical compression, shear or torsion outside the usual anatomical planes. This preliminary study outlines the mechanical behaviour and the plasticity of the vertebral structures but has been performed on only a few anatomical specimens thus not allowing statistical analysis. This would require a larger series.

Preliminary opto-electronic study on vertebral movement.

Opto-electronic systems utilising measurement of displacement of skin markers allows study of movement in the living subject. The authors have used this method in a kinematic study of the thoracic and lumbar spine measuring the displacement of skin markers placed over the spinous processes. It was possible to approach the physiological state of these complex movements once the apparatus had been calibrated to the correct level, and the error margins minimised. Repeated measurements confirmed the reliability of this method even if movement of the skin with respect to the bony reference points introduced some margin of error. Three dimensional displacement of the vertebrae were measured during voluntary movements of the spine demonstrating the complex geometry. Since opto-electronics are non-invasive they constitute an important advance in the study of the kinematics of the spine.