Lucimeris Ruaro

Proposta e validação de escala para a ferrugem alaranjada da cana-de-açúcar

The aim of this work was to elaborate and validate a diagrammatic scale to quantify the severity of orange rust of sugarcane and to compare its efficiency in assessing the disease with the scale of brown rust. For the design of the scale, 120 sugarcane leaves were collected from a susceptible cultivar and the highest and the lowest severity founded were selected as extremes of scale. The intermediate levels were calculated according to the law of Weber-Fechner. The scale was proposed with nine levels of severity: 0,06; 0,14; 0,36; 0,89; 2,17; 5,18; 11,87; 24,92 and 45,00%. The validation was accomplished by eight appraisers who estimated the severity of 120 leaves in three assessments: without scale, with scale of brown rust and with the proposed diagrammatic scale. The scale proposed was more efficient than the scale of brown rust to assess the severity of this disease, providing an average coefficient of determination (R2) of 0,91 and absence of constant and systematic errors. With the scale of brown rust, the average R2 was 0,84 and three appraisers committed constant errors. Moreover, with the scale proposed, approximately 92% of the estimates of the appraisers had been in the range of variation of 5% of the value of real severity, while in the assessments without scale and with scale of brown rust, approximately 78% and 84% of the estimates were in that range, respectively.

Influence of boron, nitrogen sources and soil pH on the control of club root of crucifers caused by Plasmodiophora brassicae

Effects of Boron (B) doses and nitrogen sources (N) at different levels of soil pH on the control of clubrootwas investigated in transplants of chinese cabbage grown in pots containing field soil.. B dissolved in water was applied at 0, 5, 10, 20 and 30 mg.kg-1 of soil of pH 5.5, 6.2 and 7.3 on the day before transplanting. N sources tested (ammonium sulfate, urea and calcium nitrate) were applied to soil of pH 5.5 and 7.3. Seedlings were inoculated with a suspension of resting spores of the pathogen at transplanting and assessed for clubroot severity after 45 days. The disease was severe (70%) when the B dose was less than 10 mg.kg-1 and the pH less than 6.0, but milder (26%) when the B dose was 10 to 30 mg.kg-1 soil at pH values higher than 6.5. Clubroot was least severe when calcium nitrate was used in soil of pH 6.5. Clubroot severity correlated negatively with concentrations of N, Ca, Mg and B in the foliage. We conclude that use of 10 to 30 mg.kg-1 boron and calcium nitrate in soil of pH 6,5 or 7,3 was effective in reducing club root severity.

Métodos de avaliação da ferrugem do álamo e eficiência de fungicidas no seu controle

Poplar rust (Melampsora medusae Thuem.) causes serious damage in the plant nursery and its control is essential to obtain good quality seedlings. This work aimed at: i) testing the efficiency of contact fungicides (mancozebe, cartap and copper oxichloride) and systemic fungicides (triadimenol, tebuconazole and difenoconazole) for poplar rust control; ii) comparing evaluation methods to discriminate the efficiency among the treatments; iii) relating defoliation and disease data and iv) verify the influence of rust control under growth tree parameters. The experiment was conducted in Sao Mateus do Sul, PR and arranged in a completely randomized design with 10 treatments (check, triadimenol, mancozebe, tebuconazole, difenoconazole, cartap, copper oxichloride, triadimenol-mancozebe, tebuconazole-mancozebe and triadimenol applied at double the interval of the previous ones) and 11 repetitions. The experimental plots were 10 m wide with 4 planting rows (space between the lines was 2.5 and between the plants, 0.50 m), totaling 110 plots with the Latorre clone. The following aspects were evaluated during two consecutive cycles: number of pustules per half leaf; visual percentage of the disease; severity per plot; visual percentage of defoliation, diameter at breast height and plant height at the end of the experiment. The systemic products (triadimenol, tebuconazole and difenoconazole) applied alone or interpolated with mancozebe were efficient in controlling the disease, reducing both the number of leaf pustules and defoliation, resulting in a significant gain in the final plant volume. Mancozebe applied alone also reduced epidemics and increased tree volume in 42%. The cupric product made the volume increase in 27%. The evaluation methods used showed differences among the treatments and there was a correlation between the disease and the damage caused to the culture.

Soil pH and inoculum concentration on the control of Plasmodiophora brassicae effect

A hernia das cruciferas causada por Plasmodiophora brassicae e uma das mais importantes doencas no cultivo de especies de Brassicas no Brasil. Nos Municipios da Regiao Metropolitana de Curitiba, PR a maioria dos solos esta contaminada pelo patogeno Plasmodiophora brassicae agente causal da hernia das cruciferas, inviabilizando o cultivo de especies de Brassicas em diversas propriedades. A calagem utilizada para elevar o pH do solo e uma das medidas de controle mais indicadas. Diante disso, o objetivo deste trabalho foi avaliar o efeito do pH do solo em diferentes concentracoes de inoculo, no controle de P. brassicae. Foram utilizados quatro niveis de pH do solo: 4,3; 5,5; 6,2 e 7,3 e tres concentracoes de inoculo:1.2 x 107 ; 2.5 x 107; e 5 x 107 esporos.mL-1 e testemunha nao inoculada. A suspensao de esporos foi obtida a partir de raizes de couve-chinesa com sintomas de hernias e adicionado no colo das plantas, por ocasiao do transplante das mudas de couve-chinesa (Brassica rapa var. pekinensis), para os vasos. Aos 45 dias apos a inoculacao, foram realizadas as avaliacoes. O efeito do pH sobre a severidade da doenca foi mais expressivo em concentracoes medias de inoculo (1.2 x 107 a 2.5 x 107 esporos.mL-1). Em concentracoes elevadas de inoculo, a severidade da doenca foi reduzida em pH do solo de 6.2 e 7.3. O melhor desenvolvimento das plantas, quantificado pelo acumulo de massa seca foliar foi obtido nos tratamentos onde o solo apresentou pH 6,2 e 7,3 e com a menor concentracao de inoculo.

RB966928: Early maturing sugarcane cultivar

RB966928 is an early to medium maturing sugarcane cultivar and in Central-Southern Brazil it is harvested between April and June; it is recommended for planting in environments with medium to high soil fertility. It stands out with a high ratoon yield and with excellent sprouting in both plant cane and ratoon cane. It is tolerant to the major diseases of economic importance of sugarcane.

Inheritance of Resistance to Orange Rust (Puccinia kuehnii) in Sugarcane Families from Crosses Between Parents with Different Orange Rust Reactions

The aim of this study was to analyze the pattern of inheritance of resistance to orange rust (Puccinia kuehnii) in sugarcane families that originated from crosses between parental clones with different rust reactions. Eighty plants of eight families resulting from crosses between two resistant genotypes, four crosses between resistant and susceptible genotypes and two crosses between susceptible genotypes were analyzed. The progenies were assessed as to its severity with a diagrammatic scale and data were submitted to Chi square test to verify the hypothesis of a gene of major effect controlling resistance. Among the eight families, only one showed a pattern consistent with the hypothesis, suggesting that the resistance to rust may be controlled by one major gene and several genes acting quantitatively. The crosses of parental clones slightly susceptible resulted in a predominantly resistant progeny. There was occurrence of transgressive segregation, because even in crosses between two highly susceptible genotypes, resistant individuals to orange rust were obtained. Therefore, susceptible parents to orange rust should not be eliminated from sugarcane breeding programs.

Podridão‑vermelha‑da‑raiz da soja em cultivos com diferentes sistemas de manejo e coberturas do solo

O objetivo deste trabalho foi avaliar o efeito dos sistemas de manejo do solo e de coberturas de inverno sobre o numero de propagulos de Fusarium spp. no solo, a incidencia da podridao‑vermelha‑da‑raiz (PVR) e a produtividade das cultivares de soja CD 206 e FT Fenix. Foram realizados dois experimentos nos anos agricolas de 2006/2007 e 2007/2008. Utilizou-se o delineamento experimental de blocos ao acaso, em parcelas subsubdivididas, com tres repeticoes. Foram avaliados dois sistemas de preparo do solo: plantio direto e revolvimento do solo na profundidade de 25 cm. As coberturas de inverno utilizadas foram: aveia‑preta, com duas densidades de plantio; aveia‑preta + ervilhaca; azevem; e pousio. A incidencia da doenca, na safra de 2006/2007, na cultivar FT Fenix, foi menor que na CD 206. Na safra 2007/2008, nao houve diferenca significativa. Houve incremento na produtividade, de 125 kg ha‑1, com o solo revolvido, em comparacao ao plantio direto. A cobertura com aveia‑preta + ervilhaca apresentou maior numero de propagulos de Fusarium spp. no solo, na safra de 2006/2007. No entanto, no segundo ano, essa diferenca nao foi observada. Os sistemas de preparo do solo e as coberturas de inverno utilizadas nao influenciam a incidencia da PVR em cultivares de soja ou o numero de propagulos de Fusarium spp. no solo. O sistema com solo revolvido proporciona aumento de produtividade da soja, no segundo ano de manejo.