Glyphosate reduces urediniospore development and Puccinia psidii disease severity on Eucalyptus grandis

BACKGROUND: Recent studies have shown the effects of glyphosate drift on decreasing rust intensity on Eucalyptus grandis plants. However, the effects of the herbicide on Puccinia psidii initial development are unknown. In this study the systemic action of glyphosate on rust severity was evaluated on Eucalyptus plants maintained under greenhouse conditions. Urediniospore germination and apressorium formation on detached leaves and on water agar medium, previously treated with glyphosate, were also evaluated. RESULTS: Rust severity and the number of urediniospores per leaf area were significantly reduced with increasing glyphosate doses, even on branches not directly treated with the herbicide, indicating a systemic effect of glyphosate on pathogen development. Similarly, higher glyphosate doses also reduced germination and apressorium formation on detached Eucalyptus leaves, regardless of the direct application of the product on the leaf limb or on the petiole base. Puccinia psidii urediniospore germination in water agar medium also decreased with increasing herbicide doses. CONCLUSIONS: Reductions in germination and apressorium formation of P. psidii urediniospores with increasing glyphosate dose indicate that a lower severity and intensity of the disease may perhaps be due to blockage of the shikimic acid pathway in the fungal metabolic system. Copyright © 2011 Society of Chemical Industry     

Fertilization of Pinus taeda L. on an acidic oxisol in southern Brazil: growth,litter accumulation,and root exploration

European Journal of Forest Research - Brazil has extensive areas planted with Pinus taeda L. primarily in southern areas with poor soil fertility and nutritional management. Identifying optimal...     

Potato minituber production from nodal cuttings compared to wholein vitro plantlets using low volume media in a greenhouse

Summary A greenhouse minituber production system involving low inputs of in vitro potato plantlets and propagation media is described, in vitro plantlets of six potato cultivars were sectioned into nodal cuttings and separately planted into moist peat based growing medium in shallow plastic trays. Cultivar differences were evident with respect to node viability, shoot regrowth and minituber yields. Nodal viability for shoot regrowth varied between 80–100%. Maximum shoot heights were recorded with whole in vitro plantlets (WIP) and the terminal Node-5 cluster. All cuttings produced minitubers. The terminal Node-5 cutting and WIP produced significantly larger minitubers >3.0 g as compared to single node cuttings. Greater numbers of minitubers were produced by the cvs Norchip, Red Pontiac and Conestoga as compared to cvs Eramosa. G8610-4PY and Shepody. Total numbers of minitubers were 3 to 5 times higher from each in vitro plantlet that was sectioned into nodal cuttings as compared with intact WIP: the yield ratios depended on cultivar.     

Genetic parameters for type classification of Nelore cattle on central performance tests at pasture in Brazil

The objective of this study was to characterize Nelore cattle on central performance tests in pasture, ranked by the visual classification method EPMURAS (structure, precocity, muscle, navel, breed, posture, and sexual characteristics), and to estimate genetic and phenotypic correlations between these parameters, including visual as well as production traits (initial and final weight on test, weight gain, and weight corrected for 550 days). The information used in the study was obtained on 21,032 Nelore bulls which were participants in the central performance test at pasture of the Brazilian Association for Zebu Breeders (ABCZ). Heritabilities obtained were from 0.19 to 0.50. Phenotypic correlations were positive from 0.70 to 0.97 between the weight traits, from 0.65 to 0.74 between visual characteristics, and from 0.29 to 0.47 between visual characteristics and weight traits. The genetic correlations were positive ranging from 0.80 to 0.98 between the characteristics of structure, precocity and musculature, from 0.13 to 0.64 between the growth characteristics, and from 0.41 to 0.97 between visual scores and weight gains. Heritability and genetic correlations indicate that the use of visual scores, along with the selection for growth characteristics, can bring positive results in selection of beef cattle for rearing on pasture.     

Mycorrhizal synthesis between Pisolithus arhizus and adult clones of Arbutus unedo in vitro and in nursery

Arbutoid mycorrhizae were synthesized between adult se-lected clones of Arbutus unedo L. and Pisolithus arhizus. Two micro-propagated clones were tested:AL1, in vitro and C1 (acclimatized plants) in nu...     

<Emphasis Type="Italic">In planta</Emphasis> multiplication and graft transmission of ‘<Emphasis Type="Italic">Candidatus</Emphasis> Liberibacter asiaticus’ revealed by Real-Time PCR

The bacterium Candidatus Liberibacter asiaticus (CLas) is associated with huanglongbing (HLB) in citrus in many countries. Despite the fact that many characteristics of the disease are known, the rate of multiplication of the bacterium within an infected tree is still poorly understood. To study this feature, we used the quantitative Real-Time polymerase chain reaction (Q-PCR) assay to follow and to quantify the multiplication of CLas in grafted infected young sweet orange plants. The rate of infection by grafting reached 100% at 120 days post-inoculation (dpi) showing that grafting could easily transmit CLas. A well-adjusted linear regression equation describing the bacterial growth in planta was obtained independently with measurements taken using repeated sampling in the same plant or different plants through the analysed period. The bacterial population, measured as copy number (CN) of the 16S rDNA target gene g⁻¹ of tissue, increased 10,000 times from 10³ at 30 dpi to approximately 10⁸ CN at 240 dpi indicating that CLas multiplication was fastest in young citrus plants. We observed a direct relationship between the concentration of pathogen and the expression of symptoms. Yellowed leaves or shoots, are commonly the first observed symptom of HLB, and were present in trees with a low amount of bacteria (10⁵ CN g⁻¹). Blotchy mottle symptoms were observed in trees with 10⁷ CN g⁻¹ of bacteria after 180 dpi. Buds taken from infected, but non-symptomatic branches were grafted on Rangpur lime and resulted in transmission rates ranging from 10 to 60%.