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Exploring the potential of plant volatiles to enhance pest management in sweet pepper plants
Get PDFHerbivore-induced plant volatiles (HIPVs) mediate plant-to-plant communication
and are received by plants as warning cues to avoid herbivore attacks. Hence, exposure to
HIPVs induces a defensive response and enhances plant resistance against phytophagous
arthropods and diseases. Furthermore, HIPVs attract beneficial organisms, including predators
and parasitoids, providing additional pest control benefits. This work highlights the role of
HIPVs as a sustainable and biorational approach to managing sweet pepper pests. In particular,
the potential of one of these HIPVs, the green leaf volatile (Z)-3-hexenyl propanoate, to control
three sweet pepper key pests, Spodoptera exigua, Frankliniella occidentalis, and Trialeurodes
vaporariorum, was assessed. In greenhouse experiments, the infestation levels of the three pests
were significantly reduced in sweet pepper plants exposed to the volatile compared to nonexposed
plants. These findings highlight the promising role of HIPVs as sustainable and
biorational tools for sweet pepper pest management. To fully exploit the benefits of this
approach, future research should focus on integrating HIVS effectively with existing pest
management strategies for sweet pepper crops
Activating tomato plant defenses reduces the damage caused by the zoophytophagous mirid Nesidiocoris tenuis
Get PDFDespite the high efficacy of the zoophytophagous Nesidiocoris tenuis as a biological
control agent, one of its drawbacks is its ability to cause damage to tomato plants. Confronted
with sucking insects, tomato plants trigger defense responses, including the production of
antioxidants or the increase of callose depositions to reduce the impact of insect piercing.
In this work, we hypothesized that the damage caused by N. tenuis in tomato plants might be
reduced by increasing the plant defenses. To do so, N. tenuis was released in defensive-induced
tomato plants and non-induced control tomato plants under greenhouse conditions. Tomato
plants were defensively induced by exposing them to the green leaf volatile (Z)-3-hexenyl
propanoate through polymeric dispensers. Nesidiocoris tenuis established in both groups of
plants (induced and non-induced), surprisingly the number of individuals was higher in the
induced plants. However, as hypothesized, the damage caused by N. tenuis was significantly
lower in the defensive-induced plants. In the defense-induced plants, the total number of
necrotic rings was reduced by half, but what was even more interesting was that the number of
severe, bent, and aborted rings decreased by almost 70 %. This result can be explained by the
increase of callose deposition in the induced plants, which helped in regenerating the plant
tissue in areas attacked by N. tenuis. Our results, by minimizing the damage caused by N. tenuis
in tomatoes, provide an opportunity for enhancing the management of N. tenuis through the
activation of the plant’s defenses
Reducing the plant damage caused by the zoophytophagous predator Nesidiocoris tenuis through genetic selection
Get PDFThe zoophytophagous predator Nesidiocoris tenuis has proven to be a highly
effective natural enemy in protected tomato key pests. In the Mediterranean basin, this
predatory mirid bug has been extensively used for the biological control of the whitefly Bemisia
tabaci and the South American tomato pinworm Tuta absoluta. However, due to its
phytophagous behavior, N. tenuis can seriously damage tomato plants when the level of prey is
scarce. Previous results using an isofemale line approach demonstrated a genetic basis for
phytophagy and zoophagy of this mirid bug. One of these isolines was selected for its relatively
lower phytophagy compared to a commercial strain. In this study, we evaluated several lifehistory
traits of the IVIA strain of N. tenuis, which has been selected for more than
50 generations, and compared them to those of a commercial strain in laboratory and
greenhouse conditions. Our results showed that the IVIA strain exhibited higher reproductive
values, greater voracity, and less damage to tomato plants, as compared to the commercial
strain. A step further, the IVIA-strain controlled B. tabaci and T. absoluta in greenhouse
experiments at the same level as the commercial strain but produced less damage to the plant.
Interestingly, the use of microsatellite markers revealed genetic differentiation between the
IVIA strain and the commercial strain. Our results highlight the potential of selective breeding
for improving biocontrol traits of interest in N. tenuis and open the door to differentiating
selected strains of N. tenuis using molecular techniques
Orujo de aceituna y bagazo de cerveza en el pienso de cerdos de cebo: resultados preliminares
Get PDFLa inclusión de subproductos agroindustriales como el orujo de aceituna (OC) y el bagazo de cerveza
(BW) en piensos es una estrategia alimentaria que puede mitigar la carga ambiental de la producción
de piensos para porcino de engorde, contribuyendo a la economía circular de la ganadería (Del Prado
et al. 2013). No obstante, para poder utilizarlos en condiciones prácticas es necesario conocer sus
efectos sobre los rendimientos productivos de los animales. Además, debido a su composición, estos
pueden tener un impacto sobre el purín (volumen y emisiones) que merece la pena ser estudiado. El
objetivo de este trabajo fue evaluar el efecto de la inclusión de OC y BW sobre los rendimientos productivos,
composición corporal y emisiones de amoniaco (NH3) del purín en cerdos de acabado
The dual benefit of plant essential oils against Tuta absoluta
Get PDFIncreasingly, plant essential oils (PEOs) are being shown as an alternative to
synthetic chemicals to fight against pests and diseases. PEOs might have a direct effect by being
toxic and repellent to pests and even attractive to natural enemies. In addition, several PEOs
have recently been described as elicitors of plant defenses, which could indirectly affect pests
and diseases. This work describes the effectiveness of five commercial PEOs (Achillea
millefolium, Allium sativum, Rosmarinus officinallis, Tagetes minuta, and Thymus zygis) on
controlling the South American tomato pinworm Tuta absoluta and the beneficial effect on the
predator Nesidiocoris tenuis. Therefore, a Y-tube olfactometer was used to test the behavioral
response of T. absoluta and N. tenuis to PEO-sprayed tomato plants and intact tomato plants.
The PEOS of Achillea millefolium and A. sativum, when sprayed on tomato plants, were found
to be significantly repellent to T. absoluta but attractive to N. tenuis; thus, these two PEOs were
selected for further studies in a greenhouse experiment. The spray of tomato plants with either
A. millefolium or A. sativum PEOs significantly reduced the number of T. absoluta eggs, larvae,
and infested leaflets. Additionally, both PEO sprays did not affect the establishment and
reproduction of the predator N. tenuis compared to the control. Interestingly, the spray of
A. millefolium and A. sativum upregulated the expression of the defence genes related to abscisic
acid (ABA), jasmonic acid (JA), and salicylic acid (SA) pathways. Plant defence activation
triggered the release of herbivore-induced plant volatiles, mainly Z-3-hexen-1-ol, heptanal,
1-octanol, (Z)-3-hexenyl propanoate, nonanal, 2-nonenal and (Z)-3-hexenyl butyrate. Our
results suggest that A. millefolium and A. sativum oils could play a significant role in T. absoluta
management. The potential of these oils as elicitor agents in tomato crops is discussed
Modeling of Grapefruit External Color as Affected by Drought Stress
Get PDFGrapefruit are well-adapted to arid and warm climatic conditions, but well-irrigated trees usually produce better-quality fruits. Because water is a major component of the fruits, there is a strong relationship between drought stress and fruits quality traits such as fruits size, external fruits color, and juice quality. The object of this study was to develop a computer model to predict postharvest external grapefruit color as a function of drought stress. During model development, drought stress was quantified using a concise water balance model based on crop evapotranspiration, precipitation, and irrigation. Data collected from Murcia, Spain, during the 2007 and 2008 growing seasons were used for model development, and the model was optimized by comparing model predictions and observations for each growing season. The root mean square error and Nash and Sutcliffe coefficient of efficiency (NSE) were used to evaluate model performance. Then, the model was evaluated with independent data collected from Florida during the 2005–06 growing season. A second-order polynomial relationship was found between external fruits color and drought stress, with less drought stress resulting in better external fruits color. Model optimization revealed good model performance for predicting external fruits color in Murcia, with NSE values of 0.975 and 0.979 for the 2007 and 2008 growing seasons, respectively. Model evaluation with the data from Florida showed that model predictions were reliable, with a NSE value of 0.984. A robust model to predict external grapefruit color as affected by drought stress was developed during the present study and could be potentially applied to supply information for suitable irrigation management of various grapefruit cultivars grown under different climatic conditions. Model performance could be confirmed by future research with data collection during further multiple seasons for different cultivars and a range of climatic condition
The Susceptibility of Bemisia tabaciMediterranean (MED) Species to Attack by a ParasitoidWasp Changes between TwoWhitefly Strains with Different Facultative Endosymbiotic Bacteria
Get PDFIn this study, two strains of the mitochondrial lineage Q1 of Bemisia tabaci MED species,
characterized by a different complement of facultative bacterial endosymbionts, were tested for their
susceptibility to be attacked by the parasitoid wasp Eretmocerus mundus, a widespread natural enemy
of B. tabaci. Notably, the BtHC strain infected with Hamiltonella and Cardinium was more resistant to
parasitization than the BtHR strain infected with Hamiltonella and Rickettsia. The resistant phenotype
consisted of fewer nymphs successfully parasitized (containing the parasitoid mature larva or pupa)
and in a lower percentage of adult wasps emerging from parasitized nymphs. Interestingly, the
resistance traits were not evident when E. mundus parasitism was compared between BtHC and
BtHR using parasitoids originating from a colony maintained on BtHC. However, when we moved
the parasitoid colony on BtHR and tested E. mundus after it was reared on BtHR for four and seven
generations, we saw then that BtHC was less susceptible to parasitization than BtHR. On the other
hand, we did not detect any difference in the parasitization of the BtHR strain between the three
generations of E. mundus tested. Our findings showed that host strain is a factor affecting the ability
of E. mundus to parasitize B. tabaci and lay the basis for further studies aimed at disentangling the role
of the facultative endosymbiont Cardinium and of the genetic background in the resistance of B. tabaci
MED to parasitoid attack. Furthermore, they highlight that counteradaptations to the variation of
B. tabaci defence mechanisms may be rapidly selected in E. mundus to maximize the parasitoid fitness
Reducing postharvest losses in persimmon. Pre and postharvest aspects involved in fruit quality and new strategies for valorization
Get PDFPersimmon is a crop of great relevance in Spain, which has become the world’s second producer and the largest exporter. This production centers mainly on cv. Rojo Brillante in the Valencian Community. In recent years however, Spain has experienced overproduction, which has led to important economic losses and increased fruit waste. Moreover, different preharvest factors, which affect fruit quality, and an inadequate postharvest management, can lead to important postharvest losses. In this context, the objective of the present Thesis is to study strategies to increase persimmon crop profitability by reducing postharvest losses and revalorizing discarded fruit and surplus production. For this purpose, the pre- and postharvest aspects involved in persimmon fruit quality are discussed. Besides, whole fruit drying is proposed as a new valorization strategy.
Of the preharvest aspects related to fruit quality parameters, the plant nutritional status is a major factor that can affect plant material composition and fruit characteristics. Thus, Chapters I and II addressed the study of macro- and micronutrients concentrations in the leaves and fruit from organic and conventional management systems, and their relation to the main fruit quality parameters in ‘Rojo Brillante’ persimmon. The main biocomponents in the fruit from both crop systems were also evaluated. The greater macro- and microelements supplied in the conventional vs. the organic system did not imply a higher accumulation of these elements in leaves and fruit. Macroelements concentration in fruit depended on the fruit flesh area evaluated (apical or basal). The correlation between macronutrients and fruit quality parameters revealed that the Ca and Mg, and the N/Ca and Ca/(K+Mg) ratios were closely related to color, firmness, total soluble solids, and soluble tannins content. The influence of crop management on fruit biocomponents concentration was observed only for malic acid, β-Cryptoxanthin and ascorbic acid, which were higher in the organic than the conventional fruit. The greatest agronomic efficiency noted in the organic crop indicates that the lower fertilization rate in such management is adequate for obtaining fruit with optimal nutrient concentrations and reveals the important role of organic matter in favoring nutrient assimilation. The results obtained in this study
provide new information about the nutritional composition of persimmon grown by organic and conventional management and reinforce the need for balanced fertilization to achieve good fruit quality.
Another preharvest aspect to consider in persimmon management is the application of phytoregulators to prolong the harvesting season. For ‘Rojo Brillante’, ethephon use is normal to advance harvest, as is gibberellic acid (GA3) to delay maturation. These treatments can affect fruit quality at both harvest and postharvest. Therefore, the postharvest 1-methylcyclopropene (1-MCP) treatment is commonly applied to guarantee postharvest fruit quality. However, the pre-harvest 1-MCP application has been shown to be a novel effective treatment for other fruit types, but with very little information for persimmon. In Chapter III, the effect of this treatment was evaluated in different scenarios combined with ethephon or GA3. The results showed that preharvest 1-MCP extended the harvest window and prolonged the commercialization period when applied to the ethephon-treated fruit. In the GA3-treated fruit, which are to be cold-stored, the preharvest 1-MCP treatment can replace the 1-MCP postharvest application, which could be a useful tool for optimizing handling operations in packinghouses.
For ‘Rojo Brillante’, an effect of harvest moment on fruit behavior during cold storage has been commercially documented. To explain these differences, in Chapter IV an in-depth physico-chemical and microstructural characterization of fruit (pretreated with GA3) during five commercial harvests (from November to December) is carried out. Moreover, the firmness changes during cold storage at 0 °C up to 90 days are evaluated. During the studied harvest period, fruit presented high firmness values, which are useful for fruit to be cold stored. Nevertheless, the minor differences revealed in persimmon firmness at harvest strongly influenced fruit behavior during cold storage. Accordingly, the fruit harvested in mid-November had the highest storage potential by maintaining firmness high for up to 90 days, which did not happen in the fruit from subsequent harvests. These differences in postharvest behavior were associated with structural parenchyma integrity at harvest.
On the other hand, it is noteworthy that deastringency treatment is one of the main steps of postharvest handling associated with postharvest losses because it directly influences final fruit quality. Although high CO2 concentrations are the most commercially applied deastringency treatment, ethanol is also employed in some countries like Brazil. With ‘Giombo’ persimmon, one of the main cultivars in this country, complete astringency loss proves difficult. In this Thesis (Chapter V), the ‘Giombo’ persimmon treated with ethanol or CO2 to remove astringency is evaluated to know the physico-chemical and microstructural changes that occur during cold storage. The results suggested that, although ethanol is the usual deastringency treatment for ‘Giombo’, high CO2 concentrations are recommended to achieve the fastest tannins insolubilization and to maintain greater flesh firmness during cold storage.
In order to valorize discarded persimmon fruit and surplus production, in this Thesis, whole fruit drying is proposed as a new strategy for ‘Rojo Brillante’. A first study (Chapter VI) approaches the physico-chemical and microstructural changes that occur during the natural-air drying of persimmon. The obtained results revealed that this variety is suitable for being subjected to the natural drying process by taking into account that the maturity stage influences final product characteristics.
To improve the drying process, convective hot-air drying is also evaluated (Chapter VII). After evaluating drying at three temperatures (35 ᵒC, 40 ᵒC and 45 ᵒC), the results showed that the higher the drying temperature, the faster the drying process was, and the final product characteristics depended on the drying temperature, especially in texture terms. Drying at 35 ᵒC resulted in a product with similar physico-chemical attributes to those achieved by the natural drying method, but in a much shorter time, which improves the commercial viability of this treatment
Non-Destructive Appraisal of Macro- and Micronutrients in Persimmon Leaves Using Vis/NIR Hyperspectral Imaging
Get PDFVisible and near-infrared (Vis/NIR) hyperspectral imaging (HSI) was used for rapid and non-destructive determination of macro- and micronutrient contents in persimmon leaves. Hyperspectral images of 687 leaves were acquired in the 500–980 nm range over 6 months, covering a complete vegetative cycle. The average reflectance spectrum of each leaf was extracted, and foliar ionomic analysis was used as a reference method to determine the actual concentration of the nutrients in the leaves. Analyses were performed via emission spectrometry (ICP-OES) for macro- and micronutrients after microwave digestion and using the Kjeldahl method to quantify nitrogen. Partial least square regression (PLS-R) was used to predict the nutrient concentration based on spectral data from the leaf using actual values of each element as predictor variables. Several methods were used to pre-process the spectra, including Savitzky–Golay (SG) smoothing, standard normal variate (SNV) and first (1D) and second derivatives (2D). Seventy-five percent of the samples were used to calibrate and validate the model by cross-validation, whereas the remaining twenty-five % were used as an independent test set. The best performance of the models for the test set achieved an R2 = 0.80 for nitrogen. Results were also satisfactory for phosphorous, calcium, magnesium and boron, with determination coefficient R2 values of 0.63, 0.66, 0.58 and 0.69, respectively. For the other nutrients, lower prediction rates were attained (R2 = 0.48 for potassium, R2 = 0.38 for iron, R2 = 0.24 for copper, R2 = 0.23 for zinc and R2 = 0.22 for manganese). The variable importance in projection (VIP) was used to extract the most influential bands for the best-predicted nutrients, which were N, K and B
Complete Genome Characterization of Penicillimonavirus gammaplasmoparae, a Bipartite Member of the Family Mymonaviridae
Get PDFIn this study, we identified Plasmopara-viticola-lesion-associated mononegaambi virus 3 (recently classified as Penicillimonavirus gammaplasmoparae), a fungi-associated mymonavirus, in grapevine plants showing an unusual upward curling symptomatology on the leaves and premature decline. Mymonaviridae is a family comprising nine genera of negative-sense single-stranded RNA viruses infecting filamentous fungi, although few of them have been associated with oomycetes, plants, and insects. Although the first mymonavirus genome description was reported a decade ago, the genome organization of several genera in the family, including the genus Penicillimonavirus, has remained unclear to date. We have determined the complete genome of P. gammaplasmoparae, which represents the first complete genomic sequence for this genus. Moreover, we provide strong evidence that P. gammaplasmoparae genome is bipartite and comprises two RNA molecules of around 6150 and 4560 nt. Our results indicate that the grapevine powdery mildew pathogen, Erysiphe necator, was also present in the analyzed plants and suggest P. gammaplasmoparae could be infecting this fungus. However, whether the fungus and/or the mycovirus are associated with the symptomatology that initially prompted these efforts remains to be determined