Marcel Bellato Spósito

Resistência a benzimidazóis por Guignardia citricarpa

The objective of this work was to evaluate the resistance of Guignardia citricarpa to pyraclostrobine and carbendazim fungicides, through: growth analysis in culture media amended with the fungicides; leaf decomposition; and production of reproductive structures on leaves naturally infected with these fungi. G.xa0citricarpa was isolated from symptomatic fruits of sweet orange (Citrus sinensis) cultivated in area with intense fungicide application. The sensibility to fungicides of G.xa0citricarpa isolates was evaluated with pyraclostrobine and carbendazim, in the doses 0.5, 1 e 2xa0µgxa0mL-1xa0a.i., to verify the effect of selection pressure caused by continuous use of these compounds. Although, reduction on leaf decomposition and on the number of reproductive structures were observed after application of pyraclostrobine and carbendazim, 7.5% of the isolates, evaluated in culture media, exhibited resistance to carbendazim, suggesting that the use of this agrochemical must be combined to other active principles in a consortium to reduce the chances of resistance occurrence. Noxa0resistance to pyraclostrobine was observed among tested isolates, what indicates that this could be an alternative compound to be used in combination to carbendazim, to minimize the chance of resistance occurrence.

Genetic variability of Brazilian isolates of Alternaria alternata detected by AFLP and RAPD techniques

The Alternaria brown spot (ABS) is a disease caused in tangerine plants and its hybrids by the fungus Alternaria alternata f. sp. citri which has been found in Brazil since 2001. Due to the recent occurrence in Brazilian orchards, the epidemiology and genetic variability of this pathogen is still an issue to be addressed. Here it is presented a survey about the genetic variability of this fungus by the characterization of twenty four pathogenic isolates of A. alternata f. sp. citri from citrus plants and four endophytic isolates from mango (one Alternaria tenuissima and three Alternaria arborescens). The application of two molecular markers Random Amplified Polymorphic DNA (RAPD) and Amplified Fragment Length Polymorphism (AFLP) had revealed the isolates clustering in distinct groups when fingerprintings were analyzed by Principal Components Analysis (PCA). Despite the better assessment of the genetic variability through the AFLP, significant modifications in clusters components were not observed, and only slight shifts in the positioning of isolates LRS 39/3 and 25M were observed in PCA plots. Furthermore, in both analyses, only the isolates from lemon plants revealed to be clustered, differently from the absence of clustering for other hosts or plant tissues. Summarizing, both RAPD and AFLP analyses were both efficient to detect the genetic variability within the population of the pathogenic fungus Alternaria spp., supplying information on the genetic variability of this species as a basis for further studies aiming the disease control.

Structural and biochemical characteristics of citrus flowers associated with defence against a fungal pathogen

The constitutive characters of plants can be structural or biochemical and play an important role in their defense against pathogens. We found that Citrus flower buds smaller than 8 mm long have constitutive structural and biochemical barriers to Colletotrichum spp. infection. In addition, this is the first time that osmophores are reported in Citrus sinensis. Our study shows that natural terpenes of Citrus flowers present a potential use for chemical control of Colletotrichum spp.

PEGAMENTO DE FRUTOS DE LARANJEIRA `PERA' EM DIFERENTES ALTURAS NA COPA RELACIONADO AOS QUADRANTES GEOGRÁFICOS

Percentage of fruit set was studied in four quadrants (Southeast, Northeast, Southwest and Northwest) in three different crown heights (low, medium and high) during five periods of flowering and fruit development. The research was conducted in Piracicaba, SP, Brazil (22o43S; 47o38W; 540m). The experimental design was randomized blocks in an 3x4x5 factorial, with 300 split-split plots. Data collected included number of flowers (first count) and number of fruits (in the other four counts). Southeast medium height presented the highest number of flowers. There was no difference among heights for number of flowers. Fruit set was different among heights. Southwest basal part of the plants showed the highest percentage of fruit set.

Agrobacterium-mediated transformation of Guignardia citricarpa: an efficient tool to gene transfer and random mutagenesis.

Guignardia citricarpa is the causal agent of Citrus Black Spot (CBS), an important disease in Citriculture. Due to the expressive value of this activity worldwide, especially in Brazil, understanding more about the functioning of this fungus is of utmost relevance, making possible the elucidation of its infection mechanisms, and providing tools to control CBS. This work describes for the first time an efficient and successful methodology for genetic transformation of G. citricarpa mycelia, which generated transformants expressing the gene encoding for the gfp (green fluorescent protein)xa0and also their interaction with citrus plant. Mycelia of G. citricarpa were transformed via Agrobacterium tumefaciens, which carried the plasmid pFAT-gfp, contains the genes for hygromycin resistance (hph) as well as gfp. The optimization of the agrotransformation protocol was performed testing different conditions (type of membrane; inductor agent concentration [acetosyringone - AS] and cocultivation time). Results demonstrated that the best condition occurred with the utilization of celluloses ester membrane; 200xa0μM of AS and 96xa0hxa0as cocultivation time. High mitotic stability (82xa0%) was displayed by transformants using Polymerase Chain Reaction (PCR) technique to confirm the hph gene insertion. In addition, the presence of gfp was observed inside mycelia by epifluorescence optical microscopy. This technique easy visualization of the behaviour of the pathogen interacting with the plant for the first time, allowing future studies on the pathogenesis of this fungus. The establishment of a transformation method for G. citricarpa opens a range of possibilities and facilitates the study of insertional mutagenesis and genetic knockouts, in order to identify the most important genes involved in the pathogenesis mechanisms and plant-pathogen interaction.

Production costs and profitability of ‘Niagara rosada’ table grape grown in different regions of São Paulo State

Niagara Rosada is the main cultivar of table grapes produced in São Paulo state. Its production is concentrated mainly in the regions of Campinas, Itapetininga and Jales, where it is grown under different production systems. The aim of this study was to analyze the economic viability of cv. Niagara Rosada at main regions producers of São Paulo State. Therefore, case studies were made with grape growers for each region to assess the production cost and calculate profitability. In the Campinas region, for two cycles per year, the main crop and the second crop were evaluated, and the Total Cost (TC) obtained was US

SUSCETIBILIDADE DE CLONES DE LIMA ÁCIDA ‘TAHITI’ À PODRIDÃO FLORAL DOS CITROS

0.81/ Kg, with US

Efficacy and timing of application of fungicides for control of citrus postbloom fruit drop

0.23/Kg of Total Net Revenue (TNR). Considering only the main crop, the decrease of grape production increased the production cost and reduced profitability, the TC reached was US

Eficiência dos fungicidas Thiabendazole + Imazalil, aplicados previamente ou em mistura à cera, no controle do bolor verde em citros

0.93/Kg and TNR US

Phylogeny, morphology and pathogenicity of Elsinoë ampelina, the causal agent of grapevine anthracnose in Brazil and Australia

0.08/Kg. In the Itapetininga region, for two cycles per year, in main crop the TC was US