Variability of the coat protein gene of Grapevine leafroll-associated virus 3 in Brazil

Leafroll is an economically important disease affecting grapevines (Vitis spp.). Nine serologically distinct viruses, Grapevine leafroll-associated virus-1 through 9, are associated with this disease. The present study describes the coat protein gene sequence of four GLRaV-3 isolates occurring in the São Francisco River basin, Northeastern Brazil. The viral RNA was extracted from GLRaV-3 ELISA-positive plants and the complete coat protein gene was amplified by RT-PCR. Sequences were generated automatically and compared to the complete coat protein sequence from North American (NY1) and Chinese (Dawanhong Nº2 and SL10) GLRaV-3 isolates. The four studied isolates, named Pet-1 through 4, showed deduced amino acid identities of 98-100% (Pet-1 through 3) and 95% (Pet-4) with North American and Chinese isolates. A total of seventeen amino acid substitutions was detected among the four characterized isolates in comparison to the NY1, Dawanhong No.2 and SL10 sequences. The results indicated the existence of natural variation among GLRaV-3 isolates from grapevines, also demonstrating a lack of correlation between sequence data and geographic origin. This variability should be considered when selecting regions of the viral genome targeted for reliable and consistent virus molecular detection.

Cotton resistance to ramulose and variability of Colletotrichum gossypii f. sp. cephalosporioides

Four cultivars and 21 lines of cotton were evaluated for resistance to ramulose (Colletotrichum gossypii f. sp. cephalosporioides) in a field where the disease is endemic. The seeds of each genotype were planted in 5 x 5 m plots with three replications. The lines CNPA 94-101 and 'CNPA Precoce 2'were used as standard susceptible and resistant references, respectively. The disease incidence (DI) was calculated from the proportion of diseased plants in the plot. The disease index (DIn) was calculated from the disease severity using a 1 to 9 scale, and was evaluated at weekly intervals starting 107 days after emergence. The data collected was used to calculate the area under disease progress curve (AUDPC). In general, the DIn increased linearly with time and varied from 20.0 to 57.1 and AUDPC from 567 to 1627 among the genotypes which could be clustered in to two distinct groups. The susceptible group contained two cultivars and nine lines and the resistant group contained one cultivar and 12 lines. The relationship between disease index and evaluation times was linear for the 25 genotypes tested. The line CNPA 94-101, used as susceptible standard, was the most susceptible with an average DI = 83.4, DIn = 57.1 and AUDPC = 1627.7. The line CNPA 96-08 with DI = 37.8, DIn = 20.0 and AUDPC = 567.7 was the most resistant one. Among the commercial cultivars 'IAC 22' was the most susceptible and 'CNPA Precoce 2', used as resistant standard was the most resistant. The variability in virulence of the pathogen was studied by spray inoculating nine genotypes with conidial suspensions (10(5)/mL) of either of the 10 isolates. The disease severity was evaluated 30 days later using a scale of 1 to 5. The virulence of the isolate was expressed by DIn. All the isolates were highly virulent but their virulence avaried for several genotypes and could be clustered in two distinct groups of less and more virulent isolates. The isolate MTRM 14 from Mato Grosso was the least virulent while Minas Gerais was the most virulent, with DIn of 6.36 and 46.47, respectively. In this experiment the line HR 102 and the cultivar 'Antares' were the most resistant ones with DIns of 18.32 and 19.14, respectively.

Physiological cost of induced resistance in cotton plants at different nitrogen levels

Resistance induction through the use of chemical inducers often results in physiological costs to the plant. In this study, induced resistance in cotton plants was evaluated with regard to physiological costs in a cultivar susceptible to Colletotrichum gossypii var. cephalosporioides (CNPA GO 2002 - 7997). Plants were cultivated in substrates with two levels of nitrogen and received two applications of acibenzolar-S-methyl (ASM), jasmonic acid (JA) and Agro-Mos® (AM) disease resistance inducers. Plant height (H), internodal length (IL), shoot fresh weight (SFW), root fresh weight (RFW), shoot dry weight (SDW) and root dry weight (RDW) were evaluated. The activity of the phenylalanine ammonia lyase (PAL) and peroxidase (POX) was also determined. The plants treated with ASM presented high physiological costs with an accentuated reduction in H, SFW and SDW, whereas those treated with JA exhibited a significant increase in SDW, and did not significantly differ from H and IL. In the potting mix supplemented with nitrogen, all inducers differed from the control treatment regarding to internodal length, whereas only ASM and AM presented a significant difference between one another in the potting mix without the addition of nitrogen. Significant correlations (P=0.05) were found for most of the variables analyzed, with greater correlations observed between SFW and SDW (0.94); IL and H (0.74); SFW and H (0.70); and SDW and H (0.70). ASM induced the least amount of PAL activity, significantly differing from the remaining treatments. Greater POX activity was observed in ASM, which significantly differed from the control. AM and JA, however, presented lower activity than the control with regard to these enzymes, and it was not possible to confirm induction resistance in these two treatments.

Genetic variability of Puccinia triticina Eriks. in Brazil

Studies on the genetic variability of Puccinia triticina in inoculum collected in Brazil started in 1941 with Vallega (20). The pioneering work in Brazil dates from 1949 (16) at "Instituto Agronômico do Sul", Ministry of Agriculture (MA), in Pelotas, Rio Grande do Sul State (RS), and continued after 1975 at Embrapa Wheat in Passo Fundo, RS. In 2002, analyses for the identification of P. triticina races continued at OR Seed breeding, simultaneously to Embrapa's program, both in Passo Fundo. The investigators involved in the identification of races in Brazil were Ady Raul da Silva in Pelotas (MA), Eliza Coelho in Pelotas (MA) and in Passo Fundo (Embrapa), Amarilis Labes Barcellos in Pelotas (MA) and in Passo Fundo (Embrapa and OR), Camila Turra in Passo Fundo (OR) and Marcia Chaves in Passo Fundo (Embrapa). From 1979 to 2010 growing season, 59 races were determined, according to the differentiation based on the expression of each Lr resistance gene. On average, one to three new races are detected per year. Research has focused on the use of vertical resistance; however, lately some institutes have searched more durable resistance, of the adult-plant type (horizontal, less race-specific). The uninterrupted monitoring of the wheat rust pathogenic population in Brazil during so many decades allowed the understanding of the evolution and virulence of races. The use of international nomenclature adopted by some programs has allowed the comparison of the fungus variability in Brazil with that in other countries, especially where frontiers are not barriers for spore transportation, confirmed by the occurrence of the same races all over one region.

RAPD analysis of genetic variability in a multiprovenance base population of Eucalyptus grandis hill ex maiden

This study aimed to evaluate the genetic variability among individuals of a base population of Eucalyptus grandis and to build a molecular marker database for the analyzed populations. The Eucalyptus grandis base population comprised 327 individuals from Coff's Harbour, Atherton and Rio Claro. A few plants came from other sites (Belthorpe MT. Pandanus, Kenilworth, Yabbra, etc.). Since this base population had a heterogeneous composition, the groups were divided according to geographic localization (latitude and longitude), and genetic breeding level. Thus, the influence of those two factors (geographic localization and genetic breeding level) on the genetic variability detected was discussed. The RAPD technique allowed the evaluation of 70 loci. The binary matrix was used to estimate the genetic similarity among individuals using Jaccard's Coefficient. Parametric statistical tests were used to compare within-group similarity of the means. The obtained results showed that the base population had wide genetic variability and a mean genetic similarity of 0.328. Sub-group 3 (wild materials from the Atherton region) showed mean genetic similarity of 0.318. S.P.A. (from Coff's Harbour region) had a mean genetic similarity of 0.322 and was found to be very important for maintenance of variation in the base population. This can be explained since the individuals from those groups accounted for most of the base population (48.3% for it). The base population plants with genetic similarity higher than 0.60 should be phenotypically analyzed again in order to clarify the tendency of genetic variability during breeding programs.

Evaluation of the physiological quality of anadenenthera peregrina (L.) Speg. seeds during storage

The aim of this experiment was to evaluate the effect of storage temperature on the viability and vigour of A. peregrina seeds. Seeds of A. peregrina harvested in Viçosa-MG, in September 2005 were used. The seeds were stored in the Laboratory of Forest Seeds Analysis (LASF) of the Universidade Federal de Viçosa (UFV), in a cold chamber, under approximately 5ºC over150 days. The seeds were stored under 20ºC for 150 days more. Seed moisture was determined after oven-drying at 105 ± 3ºC for 24 hours. The seeds were analyzed monthly using germination, tetrazolium and electrical conductivity tests and Osmopriming during 300 days, with four repetitions of 25 seeds. A. peregrina seeds kept a constant percentage of germination and viable seeds under the tetrazolium test for five months of storage, under either 5ºC and 20ºC. The electrical conductivity test showed significant differences in relation to the storage period, proving to be more sensitive than the standard germination test. Seed priming in PEG -0,4 MPa solution was not efficient in recovering the viability and vigor of the stored seeds at 5ºC and 20ºC.

Physiological and biochemical characterization of the assai palm (Euterpe oleracea Mart.) during seed germination and seedling growth under aerobic and anaerobic conditions

Physiological and biochemical aspects of assai palm during seed germination and early seedling growth were investigated. Seeds collected from plants growing in flooded and upland forests were used to determine the influence of normoxic (aerobic) and anoxic (anaerobic) conditions in germination and the initial and average time of development in the roots and shoots. After 75 days, seedlings germinated under normoxia were transferred to trays and submitted to flooding. Seed reserves (lipids, proteins, soluble sugars and starch) were monitored for quiescent and germinated seeds maintained under normoxic and anoxic conditions, as well as after 5, 10 and 20 days of seedling growth. Alcohol dehydrogenase (ADH) activity was quantified in roots and leaves of seedlings without or with flooding (partial and total). Seeds were not able to germinate under anoxia. Different strategies of storage mobilization of lipids, proteins, soluble sugars and starch were observed in seeds of each environment. ADH activity was induced by anoxia, with the highest level observed in the leaves. This study showed that, under normoxic conditions, the best developmental performance of assai palm seeds, from flooded or upland forest areas, during germination was associated with primary metabolites mobilization and seedling flooding tolerance with increased ADH activity. We conclude that the assai palm is well adapted to the anoxic conditions provoked by flooding.

Physiological quality of Gliricidia sepium (Jacq.) Steud. (Leguminosae - Papilionoideae) seeds subjected to different storage conditions

Studies of seed physiological processes represent the starting point for the sustainable utilization of native or cultivated plant species from the caatinga biome for which germination studies are still scarce. In order to determine adequate methods for the conservation of Gliricidia sepium seeds, the physiological quality of propagules exposed to different conditions and times of storage were examined. Recently collected seeds of G. sepium were analyzed immediately, while the other sample was stored for three, six, nine, or twelve months in plastic or paper bags under refrigeration or at room temperature for further analysis. The germination rates of seeds from each storage regime were determined and these rates compared to their water content. It was observed that germination capacity was directly related to changes in seed humidity. Storing seeds in plastic bags yielded the best conservation, mainly when they were stored at low temperatures. However, even at temperatures near 25°C it was possible to prolong seed viability when their water content was controlled through the use of impermeable packing.

Spatial variability of leaf wetness duration in a 'Niagara Rosada' vineyard

Despite considerable efforts to develop accurate electronic sensors to measure leaf wetness duration (LWD), little attention has been given to studies about how is LWD variability in different positions of the crop canopy. In order to evaluate the influence of 'Niagara Rosada' (Vitis labrusca) grapevine structure on the spatial variability of LWD, the objective of this study was to determine the canopy position of the ‘Niagara Rosada’ table grape with longer LWD and its correlation with measured standard LWD over turfgrass. LWD was measured in four different canopy positions of the vineyard (sensors deployed at 45º with the horizontal): at the top of the plants, with sensors facing southwest and northeast (Top-SW and Top-NE), and at the grape bunches height, with sensors facing southwest and northeast (Bottom-SW and Bottom-NE). No significant difference was observed between the top (1.6 m) and the bottom (1.0 m) of the canopy and also between the southwest and northeast face of the plants. The relationship between standard LWD over turfgrass and crop LWD in different positions of the grape canopy showed a define correlation, with R² ranging from 0.86 to 0.89 for all period, from 0.72 to 0.77 for days without rain, and from 0.89 to 0.91 for days with rain.

Effects of thermal environment and supplementation levels on the physiological parameters of moxotó goats in confined and semi-confined rising systems

The objective of this work was to determine the effect of environmental variables and supplementation levels on physiological parameters of Moxotó goats in confined and semi-confined rising systems, in the Brazilian semi-arid region. The semi-confined individuals were kept on a grass based diet during the day and arrested in the end of the afternoon. The confined animals were kept in a management center, receiving two diets composed by forage cactus and maniçoba hay into two different levels (0.5 and 1.5% of the body weight). Inside the management center and in the external environment the environmental comfort parameters were set high during the afternoon period characterizing a situation of thermal discomfort for the animals. During the morning the semi-confined animals presented an average respiratory frequency (69.5 mov min-1) and rectal temperature (39.5 ºC) higher than the confined ones (62.6 mov min-1 and 39.0 ºC, respectively). The confined and semi-confined animals were able to maintain their rectal temperature within normal limits, with increase in the cardiac beatings rate and respiratory frequency. The greater percentage of the used supplementations (1.5%) seemed to increase rectal temperature in the two studied rising systems.

Temporal variability of soil CO2 emission after conventional and reduced tillage described by an exponential decay in time model

To study Assessing the impact of tillage practices on soil carbon losses dependents it is necessary to describe the temporal variability of soil CO2 emission after tillage. It has been argued that large amounts of CO2 emitted after tillage may serve as an indicator for longer-term changes in soil carbon stocks. Here we present a two-step function model based on soil temperature and soil moisture including an exponential decay in time component that is efficient in fitting intermediate-term emission after disk plow followed by a leveling harrow (conventional), and chisel plow coupled with a roller for clod breaking (reduced) tillage. Emission after reduced tillage was described using a non-linear estimator with determination coefficient (R²) as high as 0.98. Results indicate that when emission after tillage is addressed it is important to consider an exponential decay in time in order to predict the impact of tillage in short-term emissions.