ReDivia - Repositorio Digital de l'Instit Valencià d'Investigacions Agràries
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Identification and Characterization of a Variant of Citrus viroid V (CVd-V) in Seminole Tangelo
Get PDFPrevious studies on Atalantia citroides, a citrus relative that appeared to be immune to viroid infection, revealed the existence of a new viroid, which was designated tentatively as Citrus viroid-V (CVd-V) and has been proposed as a new member of the genus Apscaviroid within the family Pospiviroidae. Biological indexing of a Seminole tangelo tree on the Etrog citron indicator followed by sPAGE analysis revealed the presence of a viroid that has been characterized as a new variant of CVd-V. The variant has 97.6% sequence identity with the reference sequence of CVd-V and shows three characteristics: (I) two compensatory changes that modify an A-U base pair between the upper and lower “strands” into a G-C base pair, (II) a U→A change located in a loop that does not seem to disturb the viroid secondary structure, and (III) two sets of changes located in the upper and lower strands that result in a rearrangement of the base pairing between the upper and lower strands. Infectivity studies performed with an artificial mutant revealed the existence of structural constraints in the region in which major differences between CVd-V and the Seminole tangelo variant were identified
Analysis of PHOTOPERIOD SENSITIVITY5 Sheds Light on the Role of Phytochromes in Photoperiodic Flowering in Rice
No full textA great number of plants synchronize flowering with day length. In rice (Oryza sativa), photoperiod is the primary environmental cue that triggers flowering. Here, we show that the s73 mutant, identified in a g-irradiated Bahia collection, displays early flowering and photoperiodic insensitivity due to a null mutation in the PHOTOPERIOD SENSITIVITY5 (SE5) gene, which encodes an enzyme implicated in phytochrome chromophore biosynthesis. s73 mutant plants show a number of alterations in the characteristic diurnal expression patterns of master genes involved in photoperiodic control of flowering, resulting in up-regulation of the floral integrator Heading date3a (Hd3a). Early heading date1 (Ehd1), an additional rice floral activator, was also highly expressed in the s73 mutant, suggesting that SE5 represses Ehd1 in wild-type plants. Silencing of Ehd1 in both Bahia and s73 backgrounds indicated that SE5 regulates Ehd1 expression. The data also indicate that SE5 confers photoperiodic sensitivity through regulation of Hd1. These results provide direct evidence that phytochromes inhibit flowering by affecting both Hd1 and Ehd1 flowering pathways
Detection and quantitation of Citrus leaf blotch virus by TaqMan real-time RT-PCR
No full textA real-time RT-PCR assay based on the TaqMan chemistry was developed for reliable detection and quantitation of Citrus leaf blotch virus (CLBV) in citrus plants. Detection by this method was highly specific and about one thousand times more sensitive than detection by conventional RT-PCR. An external standard curve using in vitro synthesized RNA transcripts of the selected target allowed a reproducible quantitative assay, with a wide dynamic range (seven logarithmic units of concentration) and very low variation coefficient values. This protocol enabled detection of as little as 100 copies of CLBV RNA in various tissues and citrus varieties infected with CLBV sources from different geographical origins. The new assay greatly improves current detection methods for CLBV and it has been most helpful for the Spanish citrus sanitation, quarantine and certification programs, and fitness evaluation of infectious cDNA clones of CLBV, useful potentially as viral vectors for citrus. (C) 2009 Elsevier B.V. All rights reserved
Diversity of Bacillus thuringiensis Strains Isolated from Citrus Orchards in Spain and Evaluation of Their Insecticidal Activity Against Ceratitis capitata
No full textA survey of Bacillus thuringiensis (Berliner) strains isolated from Spanish citrus orchards has been performed, and the strains were tested for insecticidal activity against the Mediterranean fruit fly Ceratitis capitata (Wiedemann), a key citrus pest in Spain. From a total of 150 environmental samples, 376 isolates were selected, recording a total B. thuringiensis index of 0.52. The collection was characterized by means of phase-contrast microscopy, SDS-PAGE, and PCR analysis with primer pairs detecting toxin genes cry1, cry2, cry3, cry4, cry5, cry7, cty8, cry9, cry10, cry11, cry12, cry14, cry17, cry19, cry21, cry27, cry39, cry44, cyt1, and cyt2. Diverse crystal inclusion morphologies were identified: bipyramidal (45%), round (40%), adhered to the spore (7%), small (5%), and irregular (3%). SDS-PAGE of spore-crystal preparations revealed 39 different electrophoresis patterns. All primer pairs used in PCR tests gave positive amplifications in strains of our collection, except for primers for detection of cry3, cry19, cry39, or cry44 genes. Strains containing cry1, cry2, cry4, and cry27 genes were the most abundant (48.7%, 46%, 11.2%, and 8.20% of the strains, respectively). Ten different genetic profiles were found, although a total of 109 strains did not amplify with the set of primers used. Screening for toxicity against C. capitata adults was performed using both spore-crystal and soluble fractions. Mortality levels were less than 30%. We have developed a large and diverse B. thuringiensis strain collection with huge potential to control several agricultural pests; however, further research is needed to find out Bt strains active against C. capitata
Predation by Nesidiocoris tenuis on Bemisia tabaci and injury to tomato
No full textTomato is the most important vegetable crop in Spain. The mirid bug Nesidiocoris tenuis (Reuter) commonly appears in large numbers in protected and open-air tomato crops where little or no broad-spectrum insecticides are used. Nesidiocoris tenuis is known to be a predator of whiteflies, thrips and several other pest species. However, it is also considered a pest because it can feed on tomato plants, causing necrotic rings on stems and flowers and punctures in fruits. Our objectives were to evaluate predation by N. tenuis on sweetpotato whitefly Bemisia tabaci Gennadius under greenhouse conditions and establish its relationship to N. tenuis feeding on tomato. Two different release rates of N. tenuis were compared with an untreated control (0, 1 and 4 N. tenuis plant -1) in cages of 8 m2. Significant reductions of greater than 90% of the whitefly population and correspondingly high numbers of N. tenuis were observed with both release rates. Regression analysis showed that necrotic rings on foliage caused by N. tenuis were best explained by the ratio of B. tabaci nymphs:N. tenuis as predicted by the equation y = 15.086x - 0.6359
Acta Horticulturae
No full textHigh elevation nurseries, are still considered critical use in Spain, where disinfestation before plantation is done with soil temperatures about 10 degrees C during application. Main problems are soil fungi and the presence of weeds in springtime and summer with the mother plants still developing. This research intends to study three new formulations of 1,3-dichloropropene 55.2% + chloropicrin 30.3% at 50 g/m(2) furnished by Agroquimicos de Levante SA. with the addition or not of a herbicide (trifluranyl 48% pv) at 1% and these are compared with a formula of 1,3-dichloropropene 55.4% + chloropicrin 32.7 % at 50 g/m(2), nowadays registered in Spain (ANE); methyl bromide 50%.+ chloropicrin 50% at 40 g/m(2) and a non-disinfested check. Application has been done by shank injection, as usually done, in mid-March. Crop started beginning of May. All fumigants controlled weeds except in the check treatment where weeds seized the whole plot and finally plants together with weeds were eliminated. Runners harvest results show a minor yield in treatments with herbicide as compared with those without herbicide. The nowadays registered mixture remains in an intermediate position with significant differences with methyl bromide but those without herbicide do not show statistical differences with methyl bromide. We can conclude that some adjuvants may render the mixture of 1,3-dichloropropene + chloropicrin as winter alternative to methyl bromide
Influence of Spray Equipment and Water Volume on Coverage of Citrus and Control of Citricola Scale, Coccus pseudomagnoliarum (Hemiptera: Coccidae) With Mineral Oil
No full textA trial was conducted in a commercial Citrus sinensis L. variety 'Washington' navel orange orchard to compare the coverage and efficacy against citricola scale Coccus pseudomagnoliarum (Kuwana) (Hemiptera: Coccidae) of 45.5 liters/ha of an nC24 agricultural mineral oil treatment applied by two different methods: a conventional air blast sprayer and a rotary atomizer. Three water volumes (2,340, 4,680, and 7,020 liters/ha) were applied with the air blast sprayer to determine the optimal spray volume for that equipment. A single volume (2,340 liters/ha) was applied with the rotary atomizer to compare its effectiveness with that of the air blast sprayer at this same volume. Results demonstrated that all treatments reduced citricola scale densities. Moreover, all treatments conducted with the air blast sprayer provided significantly greater coverage and significantly reduced citricola scale densities compared with the treatment made with the rotary atomizer. Larger water volume applications with the air blast sprayer did not significantly reduce citricola scale densities, although significantly better coverage was attained in the interior of the tree when spraying with 4,680 and 7,020 liters/ha. As a consequence, this study demonstrated that the increased coverage obtained by applying higher water volume with the air blast sprayer was not required for an optimal treatment in August, when the citricola scale population consisted of nymphs inhabiting the outside leaves of the tree
Genetic diversity evaluation of a loquat (Eriobotrya japonica (Thunb) Lindl) germplasm collection by SSRs and S-allele fragments
No full textLoquat (Eriobotrya japonica (Thunb.) Lindl.) is a minor Rosaceae fruit of growing interest as an alternative to the main fruit crops. In this context, the selection of new cultivars to satisfy the market demand will request the suitable characterization of the available germplasm. In this work, genetic relationships among 83 loquat accessions from different countries belonging to the European loquat germplasm collection, held at the Instituto Valenciano de Investigaciones Agrarias (IVIA) in Moncada (Spain) were evaluated using microsatellites and S-allele fragments. A total of nine single sequence repeats (SSRs) from Malus and Eriobotrya genera revealed 53 informative alleles and the S-RNases consensus primers detected 11 self-incompatibility putative alleles. The combined data allow to distinguish unambiguously 80 out of the 83 accessions studied. Unweighted pair-group method (UPGMA) cluster and principal coordinates analysis (PCoA), based on Dice’s genetic distance, generally grouped genotypes according to their geographic origins and pedigrees. Discrepancies and similarities of the results obtained with other variability analysis, based on pomological traits or molecular markers, on the same loquat collection are discussed
Delineation of Pseudomonas savastanoi pv. savastanoi strains isolated in Tunisia by random-amplified polymorphic DNA analysis
No full textTo investigate the genetic diversity of Pseudomonas savastanoi pv. savastanoi strains and to look whether these strains were distributed to geographical location. Random amplification of polymorphic DNA (RAPD) was used to discriminate between 58 Tunisian strains and 21 strains from various other countries of P. savastanoi pv. savastanoi, the causal agent of olive knot disease. Isolates were separated into three groups by cluster analysis and principal coordinate analysis of RAPD fingerprint data obtained with three primers (OPR-12, OPX-7 and OPX-14). Group 1 contained isolates from the southeast of Tunisia and European strains. Group 2 comprised strains isolated from the north of Tunisia exclusively while group 3 encompassed the majority of isolates obtained from five orchards located in the centre of Tunisia. The results indicated that isolates of P. savastanoi pv. savastanoi were genetically distinct according to geographic regions. RAPD grouped isolates derived from the same orchard as identical. This is the first application of RAPD in the delineation of P. savastanoi pv. savastanoi strains
Acta Horticulturae
No full textSpain is the first European Union producer and exporter of pomegranates (Punica granatum L.). More than 90% of Spanish commercial plantings are located in the Southeast area of the country (Alicante and Murcia provinces). The importance of the crop is rising due to worldwide increasing consumer demand for high nutritional and therapeutic quality foods. Currently, there is a clear interest in prolonging the fruit storage period to reach off-season markets. Chilling injury, weight loss and decay are the most important problems limiting storability of pomegranate. Work is in progress in our laboratory to determine the incidence and etiology of postharvest diseases in our local environmental conditions. Commercially-grown pomegranates cv. 'Mollar de Elche' from two different orchards were used in a first-season study to assess both wound pathogens (postharvest infections) and latent pathogens (field infections). We plan to continue the study during the next season. Healthy pomegranates were either artificially wounded in the rind or surface disinfected with 0.5% sodium hypochlorite and placed in humid chambers at 20 degrees C for up to 2 months. Additionally, decay was periodically assessed on intact pomegranates stored at 5 degrees C for up to 7 months. Isolates of pathogens causing fruit decay were plated in potato dextrose agar (PDA) petri dishes and incubated at 25 degrees C for further macroscopic and/or microscopic identification. Although identification of few pathogens causing minor decay is pending, preliminary results indicated that the main causal agents of wound and latent infections were Penicillium spp. and Botrytis cinerea Pers.: Fr., respectively. The same pathogens were also the most frequently isolated from cold-stored fruit. Another relatively frequent pathogen on fruit incubated at 20 degrees C was Aspergillus niger van Tiegh