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Modeling the Airborne Inoculum of Polystigma amygdalinum to Optimize Fungicide Programs Against Almond Red Leaf Blotch
Full text linkRed leaf blotch (RLB) of almond, caused by the ascomycete Polystigma amygdalinum, is a severe foliar disease endemic in the Mediterranean Basin and Middle East. Airborne ascospores of P. amygdalinum were monitored from 2019 to 2021 in two almond orchards in Lleida, Spain, and a Bayesian beta regression was used to model its seasonal dynamics. The selected model incorporated accumulated degree-days (ADD), ADD considering both vapor pressure deficit and rainfall as fixed effects, and a random effect for the year and location. The performance of the model was evaluated in 2022 to optimize RLB fungicide programs by comparing the use of model predictions and action thresholds with the standard program. Two variants were additionally considered in each program to set the frequency between applications, based on (i) a fixed frequency of 21 days or (ii) specific meteorological criteria (spraying within 7 days after rainfalls greater than 10 mm, with daily mean temperatures between 10 and 20°C, and with a minimum frequency of 21 days between applications). Programs were evaluated in terms of RLB incidence and number of applications. The program based on the model with periodic fungicide applications was similarly effective as the standard program, resulting only in a 2.6% higher RLB incidence but with fewer applications (three to four, compared with seven in the standard program). When setting the frequency between applications by using the meteorological criteria, a higher reduction in the number of applications (two to three) was observed, while RLB incidence increased by roughly 16% in both programs. Therefore, the model developed in this study may represent a valuable tool toward a more sustainable fungicide schedule for the control of almond RLB in northeast Spain
Enhancing tomato crop resilience to water stress: the role of Trichoderma afroharzianum T22 and Nesidiocoris tenuis management
Full text linkGlobal warming substantially threatens agricultural systems worldwide, with specific consequences for tomatoes,
such as increased water demands and heightened pest pressures. Adopting sustainable farming practices is imperative, and
Trichoderma species emerge as a valuable tool that enhances tomato growth, pest resilience, and stress tolerance. The integration
of this approach into existing Integrated Pest Management (IPM) strategies requires careful consideration. A paradox
arises in Southern Europe, where tomato cultivation heavily relies on predatory mirid bugs, especially Nesidiocoris tenuis,
for pest control. While N. tenuis effectively controls tomato pests, it can also harm plants by inducing callose deposits,
wilting, and yield losses, mainly when prey availability is scarce. This study delves into critical questions surrounding the
concurrent use of T. afroharzianum T-22 and N. tenuis in tomato crops under water stress. We employed a randomized block
design to examine three key factors: 1) varying levels of water stress, 2) the presence or absence of T. afroharzianum T-22
inoculation, and 3) the release or non-release of N. tenuis. Our findings demonstrate that T. afroharzianum T-22 enhances
tomato growth under water stress and mitigates the adverse impact of N. tenuis on plant development. Additionally, T. afroharzianum
T-22 inoculation did not affect N. tenuis performance, but it did reduce oxidative stress caused by N. tenuis, thus
diminishing the plant damage attributed to this predatory mirid. These results hold significance for advancing pest management
and promoting sustainable horticulture in a world grappling with the challenges of a warming climat
Optimizing sweet potato production: insights into the interplay of plant sanitation, virus influence, and cooking techniques for enhanced crop quality and food security
Full text linkThis study investigates the impact of sweet potato plant sanitation on the yield and external and internal quality root storage exploring the nutritional content affected by various cooking methods (raw, boiled, and oven-cooked). The presence of viruses, and concretely of the sweet potato leaf curl virus (SPLCV), in sweet potato propagation material is shown to significantly reduce yield and modify storage root quality. Notably, the research reveals a substantial improvement in crop yield and external quality, reinforcing the efficacy of plant sanitation methods, specifically apical meristem culture, in preserving the overall productivity of sweet potato crops. Furthermore, the investigation identifies a noteworthy decrease in starch content, suggesting a dynamic interaction between plant sanitation and starch metabolism in response to viral diseases. The study also delves into the alteration of mineral absorption patterns, shedding light on how plant sanitation influences the uptake of essential minerals in sweet potato storage roots. While the health status of the plants only slightly affected magnesium (Mg) and manganese (Mn) accumulation, indicating a potential resilience of mineral balance under virus-infected conditions. Moreover, the research identifies significant modifications in antioxidant levels, emphasizing the role of plant sanitation in enhancing the nutritional quality of sweet potatoes. Heat-treated storage roots, subjected to various cooking methods such as boiling and oven-cooking, exhibit notable differences in internal quality parameters. These differences include increased concentrations of total soluble solids (SS) and heightened levels of antioxidant compounds, particularly phenolic and flavonoid compounds. The observed increase in antioxidant capacity underscores the potential health-promoting benefits associated with plant sanitation practices. Overall, the study underscores the critical importance of plant sanitation in enhancing sweet potato production sustainability, contributing to food security, and supporting local agricultural economies. The results emphasize the need for further research to optimize plant sanitation methods and promote their widespread adoption globally, providing valuable insights into the complex relationships in food quality
Comparative genetic mapping and a consensus interspecific genetic map reveal strong synteny and collinearity within the Citrus genus
No full textIntroduction: Useful germplasm for citrus breeding includes all sexually
compatible species of the former genera Citrus, Clymenia, Eremocitrus,
Fortunella, Microcitrus, Oxanthera, and Poncirus, now merged in the single
Citrus genus. An improved knowledge on the synteny/collinearity between the
genome of these different species, and on their recombination landscapes, is
essential to optimize interspecific breeding schemes.
Method: We have performed a large comparative genetic mapping study
including several main clades of the Citrus genus. It concerns five species
(C. maxima, C. medica, C. reticulata, C. trifoliata and C. glauca), twoC. maxima x C. reticulata). The nine individual genetic maps were established
from GBS data of 1,216 hybrids.
Results and discussion: The number of SNPs mapped for each parent varies from
760 for C. medica to 4,436 for the C. maxima x C. reticulata hybrid, with an
average of 2,162.3 markers by map. Their comparison with C. clementina v1.0
assembly and inter-map comparisons revealed a high synteny and collinearity
between the nine genetic maps. Non-Mendelian segregation was frequent and
specific for each parental combination. The recombination landscape was similar
for the nine mapped parents, and large genomic regions with very low
recombination were identified. A consensus genetic map was successfully
established. It encompasses 10,756 loci, including 7,915 gene-based markers
and 2,841 non-genic SNPs. The anchoring of the consensus map on 15 published
citrus chromosome-scale genome assemblies revealed a high synteny and
collinearity for the most recent assemblies, whereas discrepancies were
observed for some older ones. Large structural variations do not seem to have
played a major role in the differentiation of the main species of the Citrus genus.
The consensus genetic map is a useful tool to check the accuracy of genome
assemblies, identify large structural variation and focus on analyzing potential
relationships with phenotypic variations. It should also be a reference framework
to integrate the positions of QTLs and useful genes identified in different analyses
horticultural groups resulting from interspecific admixture (clementine and
lemon) and two recent interspecific hybrids (C. australis x C. australasica an
Enfermedades de poscosecha de fruta fresca y métodos de control no contaminantes
Full text linkLas pérdidas económicas ocasionadas por las enfermedades de poscosecha constituyen uno de los principales problemas del sector mundial de la fruta fresca. La gran mayoría de estas enfermedades son debidas a hongos patógenos causantes de podredumbres, que pueden clasificarse en dos grupos diferentes según el momento predominante de la infección: patógenos de herida como Penicillium spp., Geotrichum spp., Rhizopus spp. o Aspergillus spp., que infectan la fruta a través de microheridas de la piel producidas justo antes, durante o después de la cosecha; y patógenos latentes como Botrytis spp., Alternaria spp., Monilinia spp., Colletotrichum spp. o Lasiodiplodia spp., que infectan la fruta en campo en cualquier momento del ciclo de desarrollo del fruto y permanecen latentes o inactivos hasta después de la recolección. Las podredumbres causadas por ambos tipos de patógenos se controlan de forma coste-efectiva con la aplicación en poscosecha de fungicidas químicos sintéticos o convencionales, como pueden ser el imazalil, el pirimetanil, el fludioxonil o el tiabendazol. Sin embargo, la aplicación masiva y continuada de estos fungicidas en las centrales hortofrutícolas conlleva importantes problemas como son la generación de residuos químicos y su presencia en la fruta, con los consiguientes riesgos para el consumidor, la proliferación de cepas fúngicas patogénicas resistentes que reduce o anula la eficacia de los tratamientos, y el acceso limitado a determinados mercados como el de residuo cero o el de producción ecológica. Por tanto, cada día urge más encontrar alternativas para el control de las enfermedades de poscosecha, incluso en producción convencional. Según su naturaleza, los tratamientos antifúngicos alternativos no contaminantes pueden ser físicos (calor, irradiaciones, atmósferas ozonizadas, …), químicos de bajo riesgo (sustancias naturales, aditivos alimentarios, recubrimientos comestibles antifúngicos, …) o biológicos (microorganismos antagónicos). Siendo no contaminantes, son también poco tóxicos y su actividad es más fungistática que fungicida, por lo cual su efectividad y persistencia son en general limitadas. Por ello, su implementación debe encuadrarse en una estrategia más amplia de control que, en cada caso particular, la coadyuve para minimizar las pérdidas económicas ocasionadas por las enfermedades. Esta estrategia, que podemos denominar ‘control integrado no contaminante de enfermedades de poscosecha’ (CINCEP), implica prestar toda la atención a los factores de precosecha, cosecha y poscosecha definitorios del triángulo de la enfermedad y, por tanto, determinantes de la incidencia final de la enfermedad. En esta ponencia, se describen los principales métodos de control alternativos, su modo de acción, sus ventajas y desventajas, y la situación actual de su adopción comercial
Reproductive Performance of Female Rabbits Inseminated with Extenders Supplemented with GnRH Analogue Entrapped in Chitosan-Based Nanoparticles
Full text linkRabbit is a reflexively ovulating species. Accordingly, in the practice of artificial insemination (AI) ovulation must be induced via exogenous GnRH (Gonadotropin-Releasing Hormone) administration, which may be performed intramuscularly, subcutaneously, or intravaginally. Unfortunately, the bioavailability of the GnRH analogue when added to the extender is lower due to the proteolytic activity in the seminal plasma and the poor permeability of the vaginal mucosa. The aim of the study was to refine the practice of AI practice in rabbits by replacing parenteral GnRH analogue administration (subcutaneous, intravenous, or intramuscular injection) with intravaginal application, while reducing its concentration in the diluent. Extenders containing the buserelin acetate in chitosan–dextran sulphate and chitosan–alginate nanoparticles were designed and 356 females were inseminated. Reproductive performance of females inseminated with the two experimental extenders, receiving 4 μg of buserelin acetate intravaginally per doe, was compared with that in the control group, the does of which were inseminated with the extender without the GnRH analogue and induced to ovulate with 1 μg of buserelin acetate administered intramuscularly. The entrapment efficiency of the chitosan–dextran sulphate complex was higher than that of chitosan–alginate. However, females inseminated with both systems showed similar reproductive performance. We conclude that both nanoencapsulation systems are an efficient way of intravaginal ovulation induction, allowing a reduction in the level of the GnRH analogue normally used in seminal doses from 15–25 μg to 4 μg
Honeydew of HLB vector, Trioza erytreae, increases longevity, egg load and parasitism of its main parasitoid Tamarixia dryi
No full textTrioza erytreae (Del Guercio) (Hemiptera: Triozidae) is one of the vectors of the citrus greening or huanglongbing (HLB) disease, the most devastating citrus disease globally. A classical biological control program has been established to control this vector in Europe, where it has been threatening the citrus industry since its detection in mainland Spain and Portugal. For this, its main parasitoid Tamarixia dryi (Waterson) (Hymenoptera: Eulophidae) has been introduced. Here, we evaluated the nutritional value of T. erytreae honeydew as a suitable food source for T. dryi. This solid honeydew is the most abundant food source for the parasitoid in the field. Our results demonstrated that T. erytreae honeydew enhanced the longevity of T. dryi compared to other diets such as water, ‘sucrose alone’ or ‘sucrose + protein’. Females fed on honeydew also oviposited more eggs than those fed on water or ‘sucrose alone’. Finally, T. dryi fed on honeydew tended to parasitize more psyllids than those fed on the other diets. Chemical analyses demonstrated that T. erytreae honeydew contains proteins, and this can explain the increase in egg load of honeydew fed parasitoids. Further research is necessary to understand why these females tended to parasitize more than females fed on ‘sucrose + protein’. Overall, these results contribute to understanding the successful and rapid establishment of T. dryi in Europe and to the successful rearing and release programs in newly invaded areas
Real-time on-site detection of the three ‘Candidatus Liberibacter’ species associated with HLB disease: a rapid and validated method
Full text linkHuanglongbing (HLB) is a devastating disease that affects all commercial citrus species worldwide. The disease is associated with bacteria of three species of the genus ‘Candidatus Liberibacter’ transmitted by psyllid vectors. To date, HLB has no cure, so preventing its introduction into HLB-free areas is the best strategy to control its spread. For that, the use of accurate, sensitive, specific, and reliable detection methods is critical for good integrated management of this serious disease. This study presents a new real-time recombinase polymerase amplification (RPA) protocol able to detect the three ‘Ca. Liberibacter’ species associated with HLB in both plant and insect samples, validated according to European and Mediterranean Plant Protection Organization (EPPO) guidelines and tested on 365 samples from nine different geographic origins. This new protocol does not require nucleic acid purification or specialized equipment, making it ideal to be used under field conditions. It is based on specific primers and probe targeting a region of fusA gene, which shows a specificity of 94%– 100%, both in silico and in vitro, for the ‘Ca. Liberibacter’ species associated with HLB. The analytical sensitivity of the new protocol is excellent, with a reliable detection limit in the order of 101 copies per microliter in HLB-infected plant and insect material. The repeatability and reproducibility of the new methods showed consistent results. Diagnostic parameters of the new RPA protocol were calculated and compared with the gold standard technique, a quantitative real-time PCR, in both crude extracts of citrus plants and insect vectors. The agreement between the two techniques was almost perfect according to the estimated Cohen’s kappa index, with a diagnostic sensitivity and specificity of 83.89% and 100%, respectively, and a relative accuracy of 91.59%. Moreover, the results are obtained in less than 35 min. All these results indicate the potential of this new RPA protocol to be implemented as a reliable on-site detection kit for HLB due to its simplicity, speed, and portability
Effect of Calcium Fertilization on Calcium Uptake and Its Partitioning in Citrus Trees
Full text linkCalcium (Ca) plays a vital role as a macronutrient in the growth and development of plants. In order of decreasing solubility, Ca can be found in vegetal tissues as soluble Ca (Fraction I), bound Ca (mainly pectates, Fraction II), inorganic insoluble Ca (mainly phosphates and carbonates, Fraction III) and organic insoluble Ca or oxalate (Fraction IV). To explore the impact of Ca fertilizer application on plant growth and its allocation among different fractions, young citrus trees were fed over a complete vegetative cycle with a 44Ca labeled fertilizer (T1-Ca), while control plants (T2) received no Ca fertilizer. The results showed that plants receiving Ca exhibited significantly greater biomass. 44Ca derived from the fertilizer was localized mainly in sink organs (new flush leaves–twigs and fibrous roots). The primary fraction responsible for total Ca partitioning was Fraction II, followed by Fraction III or IV. Citrus plants, commonly found in calcareous soils, demonstrated improved growth with calcium treatments, indicating a positive link between calcium supplementation and enhanced development. The calcium supplied through the fertilizer (44Ca) was predominantly concentrated in sink organs (mainly in Ca-pectate fraction), including new flush leaves and twigs above ground, as well as fibrous roots below ground
Rootstock-mediated physiological and fruit set responses in pepper under heat stress
Full text linkAn increase in high temperature causes major losses in pepper yields, especially in greenhouses when extending the cropping season to late spring or summer in mild climate areas. Grafting has been identified as a possible tool to cope with this abiotic stress. The objective of this study was to analyze the heat stress impact on a sweet pepper variety grafted onto rootstocks with diverse heat stress tolerances to evaluate high-temperature effects on the leaf metabolism, pollen traits and fruit set. To do so, under two greenhouses conditions (28/22°C and 38/22°C for control and heat stress, respectively), we compared the variety grafted onto two rootstocks (VA/A57 and VA/A55, tolerant and nontolerant, respectively), and used varieties ungrafted (VA) and self-grafted (VA/VA) as controls. VA/A57 obtained the lowest electrolyte leakage, non-disturbed chlorophyll and carotenoids concentration values, increased ascorbic acid and phenols concentrations, and no hydrogen peroxide accumulation. These findings indicate better predisposition to overcome heat stress than other plant combinations. Such physiological responses in leaves conferred by the tolerant rootstock coincided with the highest proline concentration in anthers, and better pollen germination and fruit set compared to the other graft combinations. We conclude that grafting peppers onto a heat stress-tolerant rootstock, such as A57, could overcome negative high-temperature effects better than an ungrafted variety. Moreover, the better physiological performance noted in vegetative parts conferred by a heat stress-tolerant rootstock would also lead to better performance in the reproductive development phase. All this indicates that using tolerant rootstocks in pepper could be an interesting method to alleviate heat stress effects on this crop