ReDivia - Repositorio Digital de l'Instit Valencià d'Investigacions Agràries
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Population genetics of cucumber mosaic virus infecting medicinal, aromatic and ornamental plants from northern Italy
No full textThe genetic variation and evolution of cucumber mosaic virus (CMV) from aromatic, medicinal and ornamental plants in northern Italy was studied by sequence analysis of the movement protein gene and comparison with equivalent sequences of isolates from other countries. Comparison of nonsynonymous and synonymous substitutions suggested that 30% of amino acid sites were under negative selection and only one was under positive selection. Phylogenetic, nucleotide diversity and genetic differentiation analyses suggested that long-distance migration plays a role in the evolution and determination of the genetic structure and diversity of CMV in northern Italy and other areas
Applications of chlorophyll fluorescence imaging technique in horticultural research: A review
No full textChlorophyll fluorescence is a rapid, non-destructive and inexpensive technique that has been used successfully in the evaluation of plant photosynthetic activity. However, this technique has been based on point measurements, and the habitual heterogeneity of photosynthetic activity over the leaf surface makes this approach highly error prone. The development of chlorophyll fluorescence imaging (CFI) overcomes this problem while including the advantages of non-imaging chlorophyll fluorescence. CFI permits the study of the spatial-temporal heterogeneities in the fluorescence emission pattern within cells, leaves or whole plants. In horticultural research, it has been mainly applied in the diagnosis of biotic or abiotic stresses in both preharvest and postharvest conditions. CFI has a useful potential to detect stresses before visual symptoms appear, which is ideal in screening of genotypes for the early identification of those with high tolerance to biotic and abiotic stress. This review provides an overview of the application of CFI in horticultural research, highlighting how CFI can be used for these purposes and in which subjects it can be applied in the future. (C) 2012 Elsevier B.V. All rights reserved
Influence of Rootstocks on Photosynthesis in Navel Orange Leaves: Effects on Growth, Yield, and Carbohydrate Distribution
No full textThe effects of two rootstocks on tree growth, fruit set and development, yield, CO2 assimilation, C-13-photoassimilates transport, and carbohydrate distribution were investigated. Cleopatra mandarin (CM) (Citrus reshni hort. ex Tanaka) and Forner-Alcaide 13 (FA-13) [Citrus reshni hort. ex Tanaka x Poncirus trifoliata (L.) Rat] rootstocks were used for this study. The first experiment was performed with 2-yr-old plants grown under greenhouse conditions. The results showed that leaves from navel orange [Citrus sinensis (L.) Osbeck] grafted onto FA-13 rootstock (navel onto FA-13) had higher net CO2 assimilation (Aco(2)) rates than those from navel orange grafted onto CM rootstock (navel onto CM). Also, FA-13 rootstock induced an increase in leaf transpiration rate with respect to CM rootstock resulting in similar water use efficiency (WUE) values. The higher of photosynthetic activity in navel onto FA-13 plants resulted in higher photoassimilate transport (C-13-labeled) from leaves to roots compared to navel onto CM plants, causing higher sucrose and starch accumulation in FA-13 roots. The second experiment was performed under field conditions using 7-yr-old trees. Navel orange grafted onto FA-13, which had the highest Aco(2) values, displayed higher photoassimilate transport (13C-labeled) from leaves to developing fruits than those on CM. navel onto FA-13 leaf sucrose content decreased compared to navel onto CM and leaf concentrations of this sugar were inversely correlated with Aco(2) values. On the other hand, sucrose and starch concentrations in root bark appeared to be related with fruit sink strength. In conclusion, FA-13 rootstock enhances photosynthetic rate in navel orange leaves compared to CM and differences in this parameter affected growth and increased yield
Recent Advances and Applications of Hyperspectral Imaging for Fruit and Vegetable Quality Assessment
Get PDFHyperspectral imaging systems are starting to be used as a scientific tool for food quality assessment. A typical hyperspectral image is composed of a set of a relatively wide range of monochromatic images corresponding to continuous wavelengths that normally contain redundant information or may exhibit a high degree of correlation. In addition, computation of the classifiers used to deal with the data obtained from the images can become excessively complex and time-consuming for such high-dimensional datasets, and this makes it difficult to incorporate such systems into an industry that demands standard protocols or high-speed processes. Therefore, recent works have focused on the development of new systems based on this technology that are capable of analysing quality features that cannot be inspected using visible imaging. Many of those studies have also centred on finding new statistical techniques to reduce the hyperspectral images to multispectral ones, which are easier to implement in automatic, non-destructive systems. This article reviews recent works that use hyperspectral imaging for the inspection of fruit and vegetables. It explains the different technologies available to acquire the images and their use for the non-destructive inspection of the internal and external features of these products. Particular attention is paid to the works aimed at reducing the dimensionality of the images, with details of the statistical techniques most commonly used for this task
Impact of fertilizer-water management on nitrogen use efficiency and potential nitrate leaching in citrus trees
No full textIn citrus production, the combination of adequate irrigation and nitrogen (N) management is considered a key factor in improving N uptake efficiency, so as to minimize nitrate (NO3-) leaching below the root zone and maintain optimal crop yield. The response of eight-year-old citrus trees grown in lysimeters to two combinations of fertilizer and water management techniques - split N application in drip irrigation (DI-F) vs. a single broadcast application with flood irrigation (FI-B) - was compared by means of the use of a N-15-labeled fertilizer (ammonium nitrate). Soil sampling 54, 116, 175 and 238 days after the beginning of the experiment and destructive harvest of trees at the end of the growing cycle allowed the determination of the fate of the labeled fertilizer supplied. The N-15 recovered in the different compartments of the plant-soil system and fertilizer nitrogen uptake efficiency (FNUE, N-15 taken up by the plant per N-15 supplied) was also quantified. Irrigation-fertilizer management practices had no effect on either total tree biomass or in fruit yield; however, a significantly greater development of coarse roots in the DI-F treatment was recorded. Fertilizer-N uptake was 25% higher in trees in the DI-F than in the FI-B treatment; fine roots and fruits of DI-F trees accumulated 2.1-and 1.4-fold higher fertilizer-N, respectively, compared to the corresponding organs of FI-B trees. At the end of the experiment, NO3--N-15 concentrations in the 0-20 cm and 60-90 cm layers of DI-F trees were higher than those in FI-B trees, whereas no differences were recorded for NH4+-(15) N concentrations of both treatments. Potential nitrate leaching (PNL) 54 days after the beginning of the experiment represented 8% of fertilizer-N-15 delivered in FI-B, whereas in DI-F it was almost negligible. In DI-F trees, PNL become noticeable on day 175, highlighting the effect of this irrigation method in reducing and slowing down the NO3- movement through the soil profile. At the end of the experiment PNL represented 14% and 5% of fertilizer supplied for FI-B and DI-F, respectively. FNUE was significantly higher (12%) with the DI-F treatment when compared to FI-B treated trees. Comparison of the two water-fertilizer management practices studied in the present work allowed us to conclude that the DI-F treatment increased FNUE while diminishing nitrate leaching, when compared to the FI-B treatment
HKT2;2/1, a K+-permeable transporter identified in a salt-tolerant rice cultivar through surveys of natural genetic polymorphism
No full textWe have investigated OsHKT2;1 natural variation in a collection of 49 cultivars with different levels of salt tolerance and geographical origins. The effect of identified polymorphism on OsHKT2;1 activity was analysed through heterologous expression of variants in Xenopus oocytes. OsHKT2;1 appeared to be a highly conserved protein with only five possible amino acid substitutions that have no substantial effect on functional properties. Our study, however, also identified a new HKT isoform, No-OsHKT2;2/1 in Nona Bokra, a highly salt-tolerant cultivar. No-OsHKT2;2/1 probably originated from a deletion in chromosome 6, producing a chimeric gene. Its 5' region corresponds to that of OsHKT2;2, whose full-length sequence is not present in Nipponbare but has been identified in Pokkali, a salt-tolerant rice cultivar. Its 3' region corresponds to that of OsHKT2;1. No-OsHKT2;2/1 is essentially expressed in roots and displays a significant level of expression at high Na+ concentrations, in contrast to OsHKT2;1. Expressed in Xenopus oocytes or in Saccharomyces cerevisiae, No-OsHKT2;2/1 exhibited a strong permeability to Na+ and K+, even at high external Na+ concentrations, like OsHKT2;2, and in contrast to OsHKT2;1. Our results suggest that No-OsHKT2;2/1 can contribute to Nona Bokra salt tolerance by enabling root K+ uptake under saline conditions
The Citrus leaf blotch virus movement protein acts as silencing suppressor
No full textTo counteract plant antiviral defense based on RNA silencing, many viruses express proteins that inhibit this mechanism at different levels. The genome of Citrus leaf blotch virus (CLBV) encodes a 227-kDa protein involved in replication, a 40-kDa movement protein (MP), and a 41-kDa coat protein (CP). To determine if any of these proteins might have RNA silencing suppressor activities, we have used Agrobacterium-mediated transient assays in the green fluorescent protein (GFP)-expressing Nicotiana benthamiana line 16c. Only CLBV MP was able to suppress intracellular GFP silencing induced by expression of either single- or double-stranded (ds) GFP RNA, but not cell-to-cell or long distance spread of the silencing signal. The MP suppressor activity was weak compared to other characterized viral suppressor proteins. Overall our data indicate that MP acts as a suppressor of local silencing probably by interfering in the silencing pathway downstream of the steps of dsRNA and small RNAs generation
Effect of postharvest degreening followed by a cold-quarantine treatment on vitamin C, phenolic compounds and antioxidant activity of early-season citrus fruit
No full textIn the Mediterranean area, many early-season citrus fruit are regularly submitted to a degreening treatment with ethylene exposure to improve their external color, and afterwards to a cold-quarantine treatment when the fruit is exported to countries free of fruit fly (Ceratitis capitata). Although the effects of the ethylene application on quality attributes as well as bioactive compounds are well documented, there is no information on the effect of the postharvest practices, including the treatment of de-greening followed by the cold-quarantine storage, on the nutritional value of citrus fruit. In this study the changes in bioactive compounds of early-season commercial citrus varieties ('Navelina' oranges and 'Clemenules', 'Clemenpons', 'Oronules', 'Prenules', 'Basol', 'Clemenrubi' and 'Orogros' clementines) submitted to a degreening treatment, without or with ethylene exposure (0 mu L/L or 2000 mu L/L C2H4, 120 h, 21 degrees C, 95% RH) and then cold-stored under quarantine conditions (1 degrees C, 16 d) plus shelf-life (20 degrees C, 7 d, 95% RH), were determined. These postharvest conditions did not induce detrimental changes in DPPH and FRAP antioxidant capacities, ascorbic acid, total ascorbic acid or total phenolic contents. Although some changes were observed in individual flavonoid compounds, these did not contribute to a loss in the total content of flavanones and flavones after ethylene degreening and the subsequent quarantine treatment. (C) 2011 Elsevier B.V. All rights reserved
Transformation of Mexican lime with an intron-hairpin construct expressing untranslatable versions of the genes coding for the three silencing suppressors of Citrus tristeza virus confers complete resistance to the virus
Get PDFCitrus 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/or intercellular level (p20 and p25) to overcome host antiviral defence. Previously, we showed that Mexican lime transformed with an intron-hairpin construct including part of the gene p23 and the adjacent 3' untranslated region displays partial resistance to CTV, with a fraction of the propagations from some transgenic lines remaining uninfected. Here, we transformed Mexican lime with an intron-hairpin vector carrying full-length, untranslatable versions of the genes p25, p20 and p23 from CTV strain T36 to silence the expression of these critical genes in CTV-infected cells. Three transgenic lines presented complete resistance to viral infection, with all their propagations remaining symptomless and virus-free after graft inoculation with CTV-T36, either in the nontransgenic rootstock or in the transgenic scion. Accumulation of transgene-derived siRNAs was necessary but not sufficient for CTV resistance. Inoculation with a divergent CTV strain led to partially breaking the resistance, thus showing the role of sequence identity in the underlying mechanism. Our results are a step forward to developing transgenic resistance to CTV and also show that targeting simultaneously by RNA interference (RNAi) the three viral silencing suppressors appears critical for this purpose, although the involvement of concurrent RNAi mechanisms cannot be excluded