Reginaldo G. Mafia

Rhizobacterial promotion of eucalypt rooting and growth

A total of 107 rhizobacterial isolates, obtained from the rhizosphere of eucalypt clones were tested as rooting inducers of cuttings and mini-cuttings planted in substrate composed of carbonized rice husk and vermiculite (1:1). Cuttings and mini-cuttings were planted in conical plastic tubes containing treated and untreated (control) substrate and kept under intermittent mist irrigation at 26-28oC. After 35 days, rooting percentage and dry root matter of cuttings were evaluated. Ten isolates capable of providing gains of up to 110% in root formation and up to 250% in root biomass over non-inoculated control cuttings were selected. Gains in rooting varied according to clone and isolate tested. The greatest gains were obtained for the mini-cuttings exhibiting the lowest rooting efficiency. Among the ten isolates tested, only 3918 (code R98) and MF4 (code R87), produced 3-indole-acetic acid in vitro, at concentrations of 0.7 and 0.67 µg ml-1, respectively. Significant increases in rooting and root dry matter of cuttings grown on rhizobacteria-inoculated substrate were found when compared to untreated or indole-butyric acid (IBA) treated mini-cuttings.

Critério técnico para determinação da idade ótima de mudas de eucalipto para plantio

Presently, mass vegetative propagation of Eucalyptus is carried out by mini-cuttings, under controlled conditions. Despite the advances of this technique, there is no criterion to determine the optimum age of the cuttings for planting, which can reflect negatively on the quality, mainly on the root system, and consequently losses may occur in the field. Hence, in the present work was established a technical criteria based on the growth speed curves and intercrossing of daily current increasing curves and daily average increasing for the variables height, root, stem and shoot biomass. Due to the restriction of exploitable volume by the root system, significant reductions in the growth speed of cuttings were found, and they must be planted preferentially from 80 (clone A) to 100 (Clone B) days of age, once older cuttings undergo a reduction in the growth speed and tend to develop root malformation problems. The implications of the low quality of the root system are the mortality of plants in the field, mainly in less favorable periods, and the consequent influence on the replanting operation, as well as on the clonal tests and a greater susceptibility of plants to environment stresses.

DETERMINAÇÃO DO TEMPO ÓTIMO DO ENRAIZAMENTO DE MINIESTACAS DE CLONES DE Eucalyptus spp.

A temporal analysis of the rooting curve of two hybrid clones of eucalypt (C1 - E. grandis x E. urophylla; C2 - E. grandis x E. saligna) was carried out to determine the optimum time for permanence of the vegetative propagules in the rooting house, considered under the technical viewpoint and risk of disease incidence. It was found out that the optimum time needed to induce rhyzogenesis depended on the Eucalyptus clone and that a knowledge of temporal model may provide a basis for the management of forest nurseries. Besides, two useful criteria were established to determine the optimum time to induce rooting, i.e., the intercept of the daily current increase curve (DCI) and daily average increase (DAI) and the time during which the maximum rooting velocity value occurs. For clones 1 and 2, respectively, 20 and 30 days were defined as optimum times, based on the criterium of the intercept of the DCI and DAI curves, while15 and 22 days were defined as optimum times, based on the maximum rooting velocity criterium, with the latter criterium being the most indicated, taking into account installation cost and risk of incidence of diseases in eucalyptus clonal propagation.

Ralstonia solanacearum em viveiros clonais de eucalipto no Brasil

The occurrence of bacterial wilt caused by Ralstonia solanacearum in eucalyptus clonal hedges in the Brazilian states of Bahia, Espirito Santo, Maranhao, Minas Gerais and Para, from April to September, 2005 resulted in loss of 553,991 rooted cuttings, 6,837,691 cuttings at rooting stage and 11,266,819 cuttings, with a total loss estimated to be at least six million reais (US

Eficiência de fungicidas sistêmicos para o controle de Cylindrocladium candelabrum em eucalipto

2.7 M). In clonal minihedges, the disease is characterized by foliar necrosis, annular or complete wood darkening, wilt and death of rooted-cuttings. Leaf symptoms are similar to those observed during the gradual death of rooted-cuttings subjected to drastic pruning or with malformed root systems. In the rooting phase, infected minicuttings can present redning of leaf blade veins and cutting rot. In the field, the disease is characterized by leaf browning and necrosis, basal leaf loss, internal wood darkening and plant death, with onset generally occurring four months after transplant. Disease severity is generally higher in trees with entangled roots and overplanting. The causal agent of the disease was confirmed through exudate tests, scanning electron microscopy, bacterial isolation, PCR/RFLP analyses, hypersensitive reactions (HR) in tobacco seedlings, pathogenicity tests in eucalyptus and tomato plantlets and reisolation of the bacteria. The production of cuttings offers a highly favorable environment for bacterial multiplication. This, combined with the lack of knowledge on genetic resistance and other disease control strategies, makes it essential to avoid introduction of this bacterium in clonal nurseries.

Crescimento de mudas e produtividade de minijardins clonais de eucalipto tratados com rizobactérias selecionadas

Several Cylindrocladium species may cause diseases in eucalyptus mini-cuttings. Although the use of fungicides is sometimes indicated, there are few studies evaluating fungicides in eucalyptus nurseries. Therefore, systemic fungicides were used against C. candelabrum to evaluate their protective, curative, and antisporulating effects, as well as their translocation and persistence in eucalyptus plants. Under in vitro conditions, azoxystrobin (AZO), triadimenol (TRI), boscalid (BOS), pyraclostrobin (PYR), carbendazim (CAR), tetraconazol (TET), tebuconazol (TEB), epoxiconazol +pyraclostrobin (EPO-PYR) and epoxiconazol (EPO), were used in the following concentrations: 0,1, 1, 5, 10, 50, 100 and 1000 µg a.i/mL. For the in vivo experiment, a clone (Eucalyptus grandis x E. urophylla) susceptible to C. candelabrum was used. The fungicides were sprayed on both leaf sides (except for the translaminar activity evaluation), the plants were allowed to dry out for 24 h, and inoculated with a 105 conidia/mL suspension. Protective effect of AZO (0.2; 0.25; 0.4; 0.65 and 0.8 g/L), EPO (0.75; 1.125; 1.5; 1.875 and 2.25 mL/L), EPO-PYR (1.25; 1.875; 2.5; 3.125 and 3.75 mL/L), PYR (0.75; 1.125; 1.5; 1.875 and 2.25 mL/L) and TEB (0.75; 1.125; 1.5; 1.875 and 2.25 mL/L), was evaluated at different concentrations. In subsequent experiments, the following fungicides (concentrations) were used: AZO (0.4 g/L), EPO (1.5 mL/L), EPO-PYR (2.5 mL/L) and TEB (1.5 mL/L). The fungicides EPO, EPO-PYR and TEB promoted protective, curative, and antisporuling effects, as well as translaminar translocation and persistence in the leaves.

Escala Diagramática para Avaliação da Severidade da Mancha Foliar do Eucalipto Causada por Quambalaria eucalypti

The effect of plant growth promoting rhizobacteria was evaluated for root biomass of cuttings, number of mini-cuttings per mini-stump and productivity of mini-clonal hedges (number of mini-cuttings x rooting percent) of eucalyptus in the nursery. Except for clone 57, all other showed increase in root biomass, with an average of 53, 52 and 69% for clones 129, 1274, and 7074 respectively. In general, significant differences were found for mini-cutting production, but not for the productivity index (number of mini-cuttings x rooting percent). Isolate S1 had a substantial effect on the production of mini-cuttings, with increases varying from 11 to 23% for clones 129 and 1274 respectively. For clone 7074, the average increase was 15%. The results clearly indicated that rhizobacteria could be employed to maximize the vegetative propagation of eucalyptus by cutting.

EFEITO DE RIZOBACTÉRIAS SOBRE O ENRAIZAMENTO E CRESCIMENTO DE CLONES DE EUCALIPTO EM DIFERENTES CONDIÇÕES DE PROPAGAÇÃO CLONAL 1

Diagrammatic scale for assessment of eucalyptus leaf spot severity caused by Quambalaria eucalypti The leaf spot, caused by Quambalaria eucalypti, is presently one of the most serious diseases in eucalyptus (Eucalyptus spp.) nurseries in Brazil. Since the disease was only reported recently in Brazil, little is known about its epidemiology and control. As standardized and precise methods are needed for the disease severity evaluations, a diagrammatic scale containing eight levels (0,4; 1; 2; 4; 8; 16; 32 and 49%) of severity was developed in this study for the disease quantification. For the scale validation four inexperienced and four expert appraisers scored leaves with different levels of severity, initially without the use of the scale and later on with its use. The estimates were compared for accuracy and precision. Using of the scale the appraisers were able to get better levels of precision and accuracy. After training, the levels of precision and accuracy were also increased, mainly for the inexperienced appraisers. The greatest errors in the disease evaluations were observed between levels 15 and 30% of severity. Additional keywords: patometry, diagrammatic scale, severity, eucalypt, Quambalaria eucalypti.

Reuse of untreated irrigation water as a vehicle of inoculum of pathogens in eucalyptus clonal nursery

The objective of this study was to evaluate the efficiency of rhizobacteria isolates in increasing rooting and growth of eucalyptus clones under different conditions of clonal propagation. Increments of both rooting and root biomass varied according to the combination rhizobacterium isolate - eucalyptus clone, and no harmful effect was observed in any of the tested combinations. Average increase in rooting was 20.4% and in root biomass was 73.0%. Isolate S2 was the most effective in increasing rooting, whereas isolates S1 and S2 most effectively increased root biomass.

Variáveis climáticas associadas à incidência de mofo-cinzento em eucalipto

Avaliou-se o risco do reaproveitamento de agua nao tratada, originaria do efluente do minijardim clonal, da casa de vegetacao, da casa de sombra, das areas de crescimento e rustificacao a ceu aberto de um viveiro clonal de eucalipto, quanto ao potencial de disseminacao de inoculo de Botrytis cinerea e Cylindrocladium candelabrum. Avaliou-se tambem a presenca de inoculo desses fungos em brita usada como cobertura do piso das areas do viveiro. Para a deteccao dos patogenos, empregaram-se discos de folhas de mamoneira (Ricinus communis) como isca. Analises periodicas evidenciaram que ambos os patogenos sao constantemente veiculados na agua nao tratada, proveniente das diferentes fases da propagacao clonal e sobre a brita, sendo C. candelabrum mais frequentemente constatado. A composicao e a concentracao de sais de tres solucoes nutritivas, expressa em valores de condutividade eletrica (0, 0,5, 1,0, 1,5, 2,0, 2,5 e 3,0 mS.cm-1), nao afetaram significativamente a germinacao de conidios.