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Comparative Analysis of Novel Lytic Phages for Biological Control of Phytopathogenic Xanthomonas spp.
Get PDFXanthomonas is an important genus of plant-pathogenic bacteria that affects agronomic and economically important crops, causing serious economic losses. In fact, several Xanthomonas species are considered regulated quarantine pests. Due to the lack of effective control measures to treat plant-pathogenic bacteria, innovative control tools are needed to carry out integrated disease management. In this regard, bacteriophages (phages), viruses of bacteria, constitute a promising biocontrol tool. In this work, we report the isolation and characterization of 11 novel Xanthomonas arboricola pv. juglandis phages belonging to different families and genera of the class Caudoviricetes. Infectivity matrix in more than 60 isolates of different xanthomonads and other phytopathogenic bacteria suggests that these phages are specific to the Xanthomonas genus, with different host ranges depending on the isolates tested. Interestingly, some of these phages showed relevant features to be used as biocontrol tools to combat pathogenic Xanthomonas spp. as important as X. oryzae or X. citri. *Importance: Phytopathogenic bacteria represent serious losses worldwide. The lack of current treatments has focused the spotlight on phages, viruses of bacteria, as very promising biocontrol tools. Phages are very specific and can help to control bacterial infections in crops, as is the case of xanthomonads-associated diseases. The discovery of new environmental phages with lytic capacity that can help to combat these pathogens is of special relevance, and it is necessary to implement phage isolation and characterization techniques to determine their host range and their genomic properties. The establishment of phage collections worldwide will allow their use as preventive, diagnostic, or therapeutic tools. Although there is still a long way to go, this work is a step forward in the implementation of new ecofriendly techniques to combat key pathogens in the field
Determining transpiration coefficients of ‘Rojo Brillante’ persimmon trees under Mediterranean climatic conditions
Get PDFThere is scarce knowledge on what are the actual water requirements of persimmon trees (Diospyros kaki). Research on this topic is required to better adjust irrigation water supplies to the actual crop water needs. This study aimed to determine the transpiration coefficients (Kp) of persimmon ‘Rojo Brillante’ trees and assess how transpiration and Kp are influenced by environmental factors and the atmospheric demand under Mediterranean climatic conditions. This was done over the course of three growing seasons by means of sap flow measurements calibrated with whole canopy gas exchange chambers. Irrigation was applied aiming to avoid water limiting conditions for trees. This was verified by monitoring the trees’ water status across the growing seasons. Sap flow measurements were linearly and highly correlated (p < 0.001) with canopy transpiration (Ep) obtained with the whole canopy chambers, but either overestimated or underestimated it. Ep increased from April until June-July in response to canopy development and increased midday canopy light interception. There was a positive linear relationship between daily Ep, reference evapotranspiration (ETo) and solar radiation. However, a non-linear relationship was obtained between Ep and vapor pressure deficit (VPD). A positive non-linear relationship (p < 0.01) was observed between Kp (Ep / ETo in non-limited water conditions) and VPD, illustrating the low stomatal regulation that persimmon trees exhibit in response to air dryness. Kp varied over the growing seasons following the ETo pattern although showing comparatively a slighter decrease during the last part of the growing season. From June to September, Kp of persimmon ‘Rojo Brillante’ trees with a midday photosynthetically active radiation (PAR) intercepted of ~30 % ranged from 0.45 to 0.56. A strong relationship was obtained between Kp and percentage of midday intercepted PAR that can be used to estimate Kp of persimmon ‘Rojo Brillante’ trees with a range of ground canopy covers. This information is useful for deriving specific water use models for persimmon trees to be implemented in decision support systems. The monthly transpiration coefficients here provided will be useful for optimizing irrigation scheduling decisions in persimmon orchards and therefore irrigation water management
Structural heterogeneity of wildflower strips enhances fructose feeding in parasitoids
Get PDFThe use of wildflower strips to provide carbohydrate resource for parasitoids and enhance pest regulation is widely recommended in agriculture. However, how the management of wildflower strips affects resource availability and utilisation by parasitoids has never been studied. Using orange orchards as a model system, three experimental alleyway management treatments were investigated: a control treatment where naturally occurring vegetation in the alleyways between rows of trees was managed under standard farm practice; a standard management wildflower treatment in which sown wildflower strips in alleyways were managed by cutting once a year; and an active management wildflower treatment, in which the wildflower strips in alleyways was managed by cutting three times a year. Wildflower strips under standard management prevented the seasonal decline of nectar, supporting fructose feeding in parasitoids across all three seasons. The abundance of floral and hemipteran honeydew carbohydrate resources in the orchard alleyways and citrus canopy was consistently greater with the standard management treatment than the control or the active management treatments. In turn, this treatment was associated with twice the abundance of primary parasitoids than with the control and active management treatments in both summer and autumn. In addition, in autumn, parasitoids were more likely to have recently fed on carbohydrate in the standard management treatment than in the other two alleyway treatments. Finally, greater carbohydrate feeding in parasitoids was associated with increased structural heterogeneity of vegetation within the orchard alleyways. This study demonstrates that the nutritional status of parasitoids in a perennial cropping system can be improved using wildflower strips, which could enhance pest regulation, and emphasises the importance of studying the management of wildflower strips when targeting specific resource requirements
From the smallest to the largest subcellular plant pathogen: Citrus tristeza virus and its unique p23 protein
Get PDFKnowledge on diseases caused by Citrus tristeza virus (CTV) has greatly increased in last decades after their etiology was demonstrated in the past seventies. Professor Ricardo Flores substantially contributed to these advances in topics like: I) improvement of virus purification to obtain biologically active virions, II) sequencing mild CTV isolates for genetic comparisons with sequences of moderate or severe isolates and genetic engineering, III) analysis of genetic variation of both CTV genomic RNA ends and features of the highly variable 5′ end that allow accommodating this variation within a conserved secondary structure, IV) studies on the structure, subcellular localization and biological functions of the CTV-unique p23 protein, and v) potential use of p23 and other 3′ -proximal regions of the CTV genome to develop transgenic citrus resistant to the virus. Here we review his main achievements on these topics and how they contributed to deeper understanding of CTV biology and to new potential measures for disease control
Genetic Control of Reproductive Traits under Different Temperature Regimes in Inbred Line Populations Derived from Crosses between S. pimpinellifolium and S. lycopersicum Accessions
Get PDFIn the present work, we study the genetic control of reproductive traits under different heat stress conditions in two populations of inbred lines derived from crosses between two S. pimpinellifolium accessions and two tomato cultivars (E9×L5 and E6203×LA1589). The temperature increase affected the reproductive traits, especially at extremely high temperatures, where only a few lines were able to set fruits. Even though a relative modest number of QTLs was identified, two clusters of QTLs involved in the responses of reproductive traits to heat stress were detected in both populations on chromosomes 1 and 2. Interestingly, several epistatic interactions were detected in the E9×L5 population, which were classified into three classes based on the allelic interaction: dominant (one locus suppressed the allelic effects of a second locus), co-adaptive (the double-homozygous alleles from the same parent alleles showed a higher phenotypic value than the combination of homozygous alleles from alternative parents) and transgressive (the combination of double-homozygous alleles from different parents showed better performance than double-homozygous alleles from the same parents). These results reinforce the important role of non-additive genetic variance in the response to heat stress and the potential of the new allelic combinations that arise after wide crosses
Evaluación del contenido de macronutrientes en caqui y su influencia en la calidad del fruto
Get PDFEl objetivo de este trabajo fue evaluar el contenido de macronutrientes en hoja y frutos de caqui ‘Rojo Brillante’ durante la cosecha y relacionarlos con los principales atributos de calidad. Se trabajó con parcelas comerciales de caqui cultivadas bajo manejo convencional o ecológico. Se realizaron tres muestreos de fruta y hojas en periodo comercial, entre mitad de octubre y mitad de diciembre
Discovery and Diagnosis of a New Sobemovirus Infecting Cyperus esculentus Showing Leaf Yellow Mosaic and Dwarfism Using Small-RNA High Throughput Sequencing
Get PDFC. esculentus is a profitable crop in Valencia, Spain, but the emergence of a disease causing of leaf yellow mosaic, dwarfism, and a drastic decrease in tuber production has become a problem. The small-RNA high-throughput sequencing (HTS) of a diseased C. esculentus plant identified only one virus, which could be the causal agent of this disease. The amino-acid comparison with viral sequences from GenBank and phylogenetic analyses indicated that this was a new species of genus Sobemovirus, and the name Xufa yellow dwarf virus was proposed. Completion with Sanger sequencing yielded a contig of 3072 nt corresponding to about 75% of the typical genome of sobemoviruses, including ORFs 2a (polyprotein-containing protease, VPG, and other proteins), 2b (RNA-dependent RNA polymerase), and 3 (coat protein). The nucleotide sequence was used to develop fast and accurate methods for the detection and quantification of xufa yellow dwarf virus (XYDV) based on reverse transcription (RT) and DNA amplification. XYDV was detected in leaves and tubers and showed a high incidence in the field in both symptomatic (almost 100%) and asymptomatic (70%) plants, but its accumulation was much higher in symptomatic plants. The relevance of these results for disease control was discussed
Fusion of Different Image Sources for Improved Monitoring of Agricultural Plots
Get PDFIn the Valencian Community, the applications of precision agriculture in multiannual woody crops with high added value (fruit trees, olive trees, almond trees, vineyards, etc.) are of priority interest. In these plots, canopies do not fully cover the soil and the planting frames are incompatible with the Resolution of Sentinel 2. The present work proposes a procedure for the fusion of images with different temporal and spatial resolutions and with different degrees of spectral quality. It uses images from the Sentinel 2 mission (low resolution, high spectral quality, high temporal resolution), orthophotos (high resolution, low temporal resolution) and images obtained with drones (very high spatial resolution, low temporal resolution). The procedure is applied to generate time series of synthetic RGI images (red, green, infrared) with the same high resolution of orthophotos and drone images, in which gray levels are reassigned from the combination of their own RGI bands and the values of the B3, B4 and B8 bands of Sentinel 2. Two practical examples of application are also described. The first shows the NDVI images that can be generated after the process of merging two RGI Sentinel 2 images obtained on two specific dates. It is observed how, after the merging, different NDVI values can be assigned to the soil and vegetation, which allows them to be distinguished (contrary to the original Sentinel 2 images). The second example shows how graphs can be generated to describe the evolution throughout the vegetative cycle of the estimated values of three spectral indices (NDVI, GNDVI, GCI) on a point in the image corresponding to soil and on another assigned to vegetation. The robustness of the proposed algorithm has been validated by using image similarity metrics
Ruptura de la autoincompatibilidad en cítricos
Get PDFEn los cítricos la autoincompatibilidad (AI) es un carácter de gran interés ya que en cultivares partenocárpicos permite la obtención de frutos sin semillas. Sin embargo, la AI supone un obstáculo para la realización de estudios genéticos y para los programas de mejora genética basados en hibridación sexual. El estrés por temperatura, la polinización de flores en estado prematuro del desarrollo (botones florales) y la poliploidización son factores que pueden inducir la ruptura de la AI. En este trabajo se ha evaluado esta ruptura en dos cultivares diploides autoincompatibles: clementina ‘Clemenules’ (C. clementina Hort. ex Tan.) y mandarino ‘Fortune’ (C. clementina x C. tangerina)
Breeding innovations in underutilized temperate fruit trees, volume II
Get PDFThis Research Topic is dedicated to the memory of our coauthor Dr. Maria Luisa Badenes, a dear colleague and friend who prematurely passed away in September 2nd, 2022. Marisa was a brilliant scientist that during her scientific career has made highly relevant contributions in genetics and breeding of diverse fruit tree crops, such as apricot, peach, loquat, kiwi or persimmon. But, even more important, Marisa has been a generous colleague and an excellent person whose work will continue in the hands of the numerous scientists that have been mentored under her guidance or have collaborated with her. We all in the fruit breeding community will surely miss her