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Assessment of a Remote Sensing Energy Balance Methodology (SEBAL) Using Different Interpolation Methods to Determine Evapotranspiration in a Citrus Orchard
Get PDFA surface energy balance algorithm for land (SEBAL) for estimating evapotranspiration (ET) has been parameterized and tested in a 400-ha drip irrigated citrus orchard. Simultaneously, during three growing seasons, energy fluxes were measured using Eddy Covariance. Instantaneous fluxes obtained with SEBAL using 10 images from Landsat-5 were compared with the measured fluxes. The Perrier function was the best method for properly estimating the roughness momentum length for discontinuous canopies, as in citrus orchards. Crop height was estimated using LIDAR data. In general, SEBAL performed well for net radiation estimation but failed in soil heat flux estimation. Latent heat estimations from the SEBAL model had a relative root mean square error (rRMSE) of 0.06 when compared with measurements obtained by Eddy Covariance. Three procedures were tested for up-scaling the instantaneous ET estimates from SEBAL to daily ET values: 1) assuming the fraction between the actual ET and the reference ET is constant throughout the day; 2) using actual local crop coefficient curves; and 3) using an up-scaling factor where the fraction of hourly ET to daily ET equals the ratio of hourly to daily global solar radiation. This last method gave acceptable results for daily ET estimations (rRMSE = 0.09) and for 15day ET (rRMSE = 0.19), and its main advantage is that no local data are required. It is concluded that the SEBAL methodology can be successfully applied for determining actual ET, even in discontinuous citrus canopies. However, additional parameterizations of momentum roughness length were needed in order to obtain reliable ET determinations
Acta Horticulturae
No full textThree paraben sodium salts (p-hydroxy-benzoate) were evaluated as postharvest treatments to control citrus green (GM) and blue (BM) mold, caused by Penicillium digitatum and Penicillium italicum, respectively. The curative activity of sodium methyl (SMP; at 0.1, 1, 10, 40, 70, 100, 150, 200 and 250 mM), ethyl (SEP; at 0.1, 1, 10, 20, 30, 40, 70, and 100 mM) and propyl (SPP; at 0.1, 1, 4, 7, 10, and 100 mM) paraben were evaluated on ‘Valencia’ oranges by inoculating the pathogens in rind wounds and, about 24 h later, placing a drop of the solutions in the same rind wound. Disease development was assessed on fruit incubated at 20°C for 6 days. All three paraben salts reduced mold development. Concentrations of 150, 200 and 250 mM of SMP were the most effective and completely controlled both diseases. Concentrations of 20, 30, 40, 70 and 100 mM of SEP reduced the incidence of GM and BM by 100, 94, 100, 100 and 73% and 87, 62, 93, 100 and 80%, respectively. Concentrations of 7, 10 and 100 mM of SPP reduced the incidence of GM and BM by 94, 89 and 94% and 70, 88 and 100%, respectively. Most of these concentrations of SMP, SEP and SPP also significantly reduced the severity of GM and BM. SMP at 200 mM, SEP at 70 mM and SPP at 100 mM were, among the range of concentrations tested, selected as the best to be used in further research
Harvest and postharvest quality of persimmon fruit: physicochemical and nutritional aspects
Get PDFIn recent years, persimmon crop has become very relevant in Mediterranean Spain, where the production of this fruit centres on only one variety, persimmon cv. Rojo Brillante, majorly located in the Valencian Community. The main postharvest disorders manifested by ‘Rojo Brillante’ persimmons are flesh browning, which is associated with mechanical damage and chilling injury displayed after low-temperature storage. Previous research has determined the postharvest conditions that lead fruit to develop such alterations. However, the biochemical process behind flesh browning and chilling injury disorders is still unknown. Currently, there is special interest in introducing cultivars from other countries to broaden the varietal range. Besides, prolonging the fruit storage period to supply the markets according to the demand is one of the main challenges. In this context, the present Thesis approached three main objectives: 1) Studying the biochemical process implied in the main physiological postharvest disorders manifested in persimmon fruits by focusing on changes in the fruit redox state; 2) Evaluating postharvest treatments to preserve fruit quality during cold storage; 3) Assessing the physico-chemical and nutritional quality of persimmon cultivars introduced from other countries to increase the varietal range
Acta Horticulturae
No full textCitrus tristeza virus (CTV), the causal agent of the most devastating viral disease of citrus, has evolved three silencing suppressor proteins acting at intra-(p23 and p20) and inter-cellular level (p20 and p25) to overcome host antiviral defense. RNA interference (RNAi), an approach based on using dsRNA to trigger RNA silencing, has been widely used for generating transgenic plants resistant against viruses. Considering the important role of p23, p20 and p25 in CTV pathogenesis, we obtained transgenic Mexican lime plants with an intron-hairpin vector carrying full untranslatable versions of genes p25, p20, p23 and the 3'-UTR from the CTV strain T36, to attempt silencing their expression in CTV-infected cells. Complete resistance to viral infection was observed in three transgenic lines, with all their propagations remaining symptomless and virus-free after graft-inoculation with CTV-T36, either in the non-transgenic rootstock or directly in the transgenic scion. Accumulation of transgene-derived siRNAs was necessary but not sufficient for CTV resistance. When immune transformants were challenged with a dissimilar CTV strain the resistance was partially broken, stressing the importance of sequence identity in the underlying RNAi mechanism. This is the first evidence that it is possible to achieve full resistance to CTV in a highly sensitive citrus host by targeting simultaneously its three viral silencing suppressors through RNAi
Effects of a commercial calcium protein hydrolysate on the salt tolerance of Diospyros kaki L. cv. "Rojo Brillante" grafted on Diospyros lotus L.
No full textDiospyros lotus L. is advantageously used as rootstock for Diospyros kaki L. cv. “Rojo Brillante” in most plantations of Eastern Spain. However, one of the few drawbacks of D. lotus L. as rootstock, is the high sensitivity to soil salinity, and specifically chloride, it imparts to the scion, which is visually detected as an extensive late season leaf necrosis. Several complex mixtures of organic polymers such as calcium protein hydrolysates (CPH) have been recommended to counteract salt stress on plants. Nevertheless, the effects of these commercial complex products on tree crops, are not usually rigorously studied, nor satisfactorily explained. The effects on soil and plant of the addition of a commercial CPH in the irrigation water of a D. kaki L. cv. “Rojo Brillante” plantation grafted on D. lotus L. were studied during two successive seasons. Soil salinity and chloride contents, significantly, but slightly, increased in CPH treated subplots, while at the same time leaf chloride contents decreased. These effects suggest a lower chloride plant uptake in CPH treated subplots. The lower chloride uptake in CPH treated trees was accompanied by less leaf necrosis, and also lower leaf water potential. However, the yields of CPH treated and non-treated trees were statistically non-different. The build-up of compatible solutes, mainly proline and glycine betaine, in addition to the biosynthesis of salt-stress-response proteins, which would have been stimulated by the CPH, could explain the observed effects. However, the likely biosynthesis of all these substances may have drawn plant resources from fruit development, thus explaining why yields were the same in treated and non-treated subplots despite the trees in treated subplots showed better adaptation to soil salinity
Acta Horticulturae
No full textAlternaria brown spot (ABS) of mandarins, caused by a pathotype of the fungus Alternaria alternata, is a serious disease both in humid and semi-arid citrus-growing regions of the world. The pathogen affects leaves and fruit of susceptible mandarin cultivars such as 'Fortune', 'Nova', 'Minneola', and 'Murcott'. The epidemiology of ABS was studied mainly in humid areas in Florida but, due to climatic differences, this information cannot be extrapolated to semi-arid regions like Spain. Field studies were conducted in 2011 in the experimental orchards at IVIA, Valencia. Dynamics of the airborne Alternaria conidia were monitored weekly by a spore trap, and the percentage of pathogenic isolates was determined periodically using the selective medium, ARSA, and pathogenicity tests. The presence of inoculum on affected leaves, shoots, leaf litter, and weeds was also determined. Infection periods were monitored weekly by exposing trap or indicator plants of 'Fortune' and 'Nova' mandarins. Environmental variables were recorded by an automated meteorological station. Although Alternaria conidia were detected through the experimental period, only 5% of all the isolates were pathogenic. As affected leaves and shoots were determined to be the main source of inoculum, the survival of the fungus in the leaf litter was higher than previously reported in Florida. Pathogenic isolates were detected also in weeds, but only at very low levels. Infections in trap plants occurred mainly in May-June and September-October. A significant positive correlation was detected between disease incidence and rainfall
Effects of nutrition on digestion efficiency and gaseous emissions from slurry in growing-finishing pigs. I. Influence of the inclusion of two levels of orange pulp and carob meal in isofibrous diets
No full textAn experiment was conducted to investigate the effects of increasing the level of two sources of fibrous by-products, orange pulp (OP) and carob meal (CM), in iso-NDF growing-finishing pig diets on nutrient balance, slurry composition and potential ammonia (NH3) and methane (CH4) emissions. Thirty pigs (85.4 +/- 12.3 kg) were fed five iso-nutritive diets: a commercial control wheat/barley (C) and four experimental diets including two sources of fibrous by-products (OP and CM) and two dietary levels (75 and 150 g/kg) in a 2 x 2 factorial arrangement. After a 14-day adaptation period, faeces and urine were collected separately for 7 days to measure nutrient digestibility and the excretory patterns of N from pigs (6 replicates per diet) housed individually in metabolic pens. For each animal, the derived NH3 and CH4 emissions were measured in samples of slurry over an 11- and 100-day storage periods, respectively. Source and level of the fibrous by-products affected digestion efficiency in a different way as the coefficients of total tract apparent digestibility (CTTAD) for dry matter (DM), organic matter (OM), fibre fractions and gross energy increased with OP but decreased with CM (P<0.05). Crude protein CTTAD decreased with the inclusion of both sources of fibre, being lower at the highest dietary level. Faecal concentration of fibre fractions increased (P<0.05) with the level of inclusion of CM but decreased with that of OP (P<0.01). High dietary level for both sources of fibre increased (P<0.02) CP faecal content but urine N content decreased (from 205 to 168 g/kg DM, P<0.05) in all the fibre-supplemented compared to C diet. Additionally, the proportions of undigested dietary, water soluble, and bacterial and endogenous debris of faecal N excretion were not affected by treatments. The initial slurry characteristics did not differ among different fibre sources and dietary levels, except pH, which decreased at the highest by-product inclusion levels. Ammonia emission per kg of slurry was lower in all the fibre-supplemented diets than in C diet (from 2.44 to 1.81 g, P< 0.05). Additionally, slurries from the highest dietary level of by-products tended (P< 0.06) to emit less NH3 per kg of initial total Kjeldahl N and showed a lower Bo, independently of the fibre source. Thus, the fibre sources and their dietary levels affected pig nutrient digestion and composition of urine and faeces, showing potential to decrease NH3 and CH4 emissions at high levels of inclusion, independently of type of fibre. C) 2015 Elsevier B.V. All rights reserved
Salt tolerance traits revealed in mandarins (Citrus reticulata Blanco) are mainly related to root-to-shoot Cl- translocation limitation and leaf detoxification processes
No full textMandarin is an important genetic group in citrus largely used for variety breeding programs and also to generate new rootstocks better adapted to abiotic stress. In this study, 14 mandarin accessions representative of the diversity in this group were analyzed for their salt stress tolerance properties. Physiological parameters such as gas exchange, osmotic pressure, as well as leaf and root chloride contents were measured. Samples were harvested to characterize the presence of hydrogen peroxide and to monitor the activity of enzymes involved in reactive oxygen species synthesis and detoxification processes. Very different physiological behaviors were noted among accessions. Most cultivars that are used as rootstocks such as Citrus reshni Hort. ex Tan. (‘Cleopatra’) or Citrus depressa Hayata (‘Shekwasha’), were found to be tolerant, with limited root-to-shoot chloride translocation. Also, some accessions used as varieties showed similar tolerance traits. Interestingly some accessions that presented high leaf chloride contents were not always associated with sensitivity traits. Also accessions such as ‘Willowleaf’ showed quite high leaf chloride contents that were correlated with better detoxification processes. Tolerance traits that we identified are discussed in relation to the known genetic structure in mandarins. Finally, some of the salt stress tolerant accessions that we identified could potentially be used as parents in rootstock breeding programs and others in scion variety breeding programs
Short-term high CO2 treatment alleviates chilling injury of persimmon cv. Fuyu by preserving the parenchyma structure
No full textPersimmon cv. Fuyu is chilling-sensitive and manifests chilling injury symptoms, flesh gelling and fruit darkening, during cold storage and subsequent shelf life. The objective of this study was to evaluate the effect of short-term high CO2 treatments on chilling injury manifestation of 'Fuyu'. Short-term high CO2 treatments consisted in maintaining fruit in a 95% CO2 atmosphere for 0, 12, 24 or 36 h before storage at 1 degrees C. After 35 d and 50 d of low-temperature storage and after subsequent shelf-life periods of 5 d at 20 degrees C, fruit quality and microstructural changes of flesh were evaluated. Our results showed that short-term high CO2 treatments alleviate the main chilling injury symptoms, flesh gelling and fruit darkening. The longer the treatment, the greater chilling injury alleviation becomes. The microstructural study revealed that flesh gelling is associated with a complete disruption of cell walls and membranes, which led to the total loss of the initial parenchyma structure. Short-term high CO2 treatment alleviated flesh gelling by preserving the integrity of cells walls and plasmalemma. (C) 2014 Elsevier Ltd. All rights reserved
Embryogenic response from anther culture of cultivars of loquat (Eriobotrya japonica (Thunb.) Lindl.) from different origins
No full textHomozygous lines are very interesting for genetic studies and in plant breeding. These can be produced in a single step via haploidy. Production of haploids in loquat (Eriobotrya japonica (Thunb.) Lindl.) would be of considerable value. In this study, androgenesis by anther culture was used to regenerate loquat plants. Different variables related to the induction of embryogenesis were tested, including the temperature pretreatment of flower buds, various levels of growth regulators in the culture medium, and genotypic effects. Eight cultivars of loquat from different geographic origins were used. The first step, the association between floral bud size and the corresponding microspore/pollen developmental stages was established for the different cultivars. Bud sizes of 6.5–7.0 mm, corresponded to the uninucleate microspore stage and provided the highest callogenesis levels. Pre-treatment of flower buds at 4 °C for had a negative effect on anther response and only the 4-day pre-treatment resulted in callus formation at all. The highest percentage of morphogenetic calli was obtained on medium supplemented with 4.56 μM zeatin (Z) and 5.36 μM 1_naphthalene acetic acid (NAA) in cvs. ‘Changhong-3’ (27 %), ‘Jiefanghong’ (30 %) and ‘Moggi Wase’ (36 %). Following a transfer of morphogenetic calli to the embryo induction medium, six embryos were obtained from cv. ‘Jiefanghong’; and one of them developed into a plantlet. Flow cytometry and chromosome counts revealed that the plantlet was triploid. The single triploid plant obtained was unexpected and its origin is obscure. One possible explanation is that it arose from fusion of sperm nucleus and two vegetative nuclei