Roberto Antonio Rodella's research while affiliated with São Paulo State University and other places

The fungus Austropuccinia psidii infects young tissues of Eucalyptus plants until they are two years old in the nursery and field, causing Myrtaceae rust. The characteristics making older eucalypt leaves resistant to A. psidii and the reason for the low levels of this pathogen in older plants need evaluations. The aim of this study was to evaluate the morphological differences between Eucalyptus grandis leaves of different growth stages and two plant ages to propose a visual phenological scale to classify E. grandis leaves according to their maturation stages and to evaluate the time of leaf maturation for young and adult plants. A scale, based on a morphological differentiation for E. grandis leaves, was made. The color, shape and size distinguished the leaves of the first five leaf pairs. Anatomical analysis showed a higher percentage of reinforced tissue, such as sclerenchyma-like tissue and collenchyma, greater leaf blade thickness, absence of lower palisade parenchyma in the mature leaves and a higher number of cavities with essential oils than in younger ones. Changes in anatomical characteristics that could reduce the susceptibility of older E. grandis leaves to A. psidii coincide with the time of developing leaf resistance. Reduced infection of this pathogen in older plants appears to be associated with a more rapid maturation of their leaf tissues.

The total area of forest crops in Brazil is 9.55 million hectares, of which 7.5 million hectares are Eucalyptus. These crops are the most productive in the world, but may suffer losses due to exotic pests, including Glycaspis brimblecombei Moore (Hemiptera: Aphalaridae) found in Brazil since 2003. Interactions between Eucalyptus plants and insect pests may led to the selection of resistant genotypes. Eucalyptus species are either susceptible or resistant to this pest group, but the damage they suffer needs to be evaluated. The objective was to determine possible leaf anatomy indicators of different Eucalyptus species associated with G. brimblecombei infestations, focusing on plant resistance to this pest. The study was carried out with Eucalyptus camaldulensis, Eucalyptus grandis, Eucalyptus saligna and Eucalyptus urophylla saplings infested or not by G. brimblecombei eggs and nymphs. Eighteen anatomical characteristics of the leaves of these plants were analyzed. The number of stomata on the adaxial and abaxial sides and the glandular area in the central leaf vein are associated with greater or lesser infestation by G. brimblecombei in the Eucalyptus genotypes.

The fungus Austropuccinia psidii is a major pathogen of Eucalyptus spp. that damages mainly early-stage leaves. Resistant clones are the most widely used control measure for the rust disease caused by A. psidii. Essential oils produced in the plant-host cells are associated with resistance. However, the chemical characteristics of Eucalyptus leaves at different stages of maturity, associated with resistance or susceptibility to A. psidii, needs to be determined. The aim of this study was to characterize the chemical composition of essential oils in Eucalyptus leaves at three developmental stages of clones of three Eucalyptus urophylla × Eucalyptus grandis hybrids that exhibit different resistance levels to rust, and to identify probable resistance-related compounds from them. The severity of the rust following inoculation and the quantity and quality of the essential oil extracted by hydrodistillation were determined at the first, third and fifth leaf stages of the three clones. Identification of the compounds present in the essential oil was determined by gas chromatography coupled with mass spectrometry. No rust was observed on the three leaf stages of the resistant clone or on the fifth leaf stage of the susceptible clones. Limonene was found at high percentages in essential oils from the three leaf stages of the resistant clone and at low percentages in the susceptible clones. In vitro and in vivo tests indicated that low limonene percentages stimulated A. psidii urediniospore germination and were not fungitoxic, whereas high percentages caused complete inhibition of germination and degenerative changes in fungal reproductive structures. The limonene present in Eucalyptus leaves can be considered a chemical compound related to the rust resistance of Eucalyptus spp.

Abstract: Rust is a major Eucalyptus spp. disease; which is especially damaging for early-stage plants. The aim of this study was to verify the pre-infection process of Austropuccinia psidii in the leaves of three phenological stages of Eucalyptus clones with different resistance levels. Plants from the hybrids of Eucalyptus urophylla × E. grandis with variable levels of resistance to this disease were used. The pathogen was inoculated in vitro on abaxial leaf discs of first; third and fifth leaf stages and maintained under conditions suitable for disease development. Subsequently; samples from these discs were collected and 120 h after inoculation and processed using scanning electron microscopy analysis. No symptoms were seen in any leaf stage of the resistant clone. Additionally; a low incidence of A. psidii germination (1.3-2%) and appressoria (0-0.5%) in three leaf stages was observed. However; the first leaf stages of the susceptible clone presented germination of large numbers of urediniospores (65%) with appressoria (55%) and degradation of the cuticle and wax. From the third stage; the percentage of germinated urediniospores (<15%) and appressoria (<2%) formation of this clone decreased. Protrusions on the leaf surface; associated with the pathogen; were observed on the first and third leaf stages of the resistant clone and on the fifth stage of the susceptible clone suggesting a possible defensive plant reaction. Keywords: Eucalypt rust; pathogenesis; phenological stage leaves; pre-infection stage; resistance; leaf discs; scanning electron microscopy; Puccinia psidii.

Objetivou-se com esse trabalho avaliar a seletividade de herbicidas aplicados em pós-emergência sobre Paspalum notatum L. (grama Batatais), bem como relacionar a seletividade destes herbicidas com a anatomia foliar desta espécie de grama. Os tratamentos constituíram-se pela aplicação dos herbicidas bentazon (720 g ha-1), nicosulfuron (50 g ha-1), halosulfuron (112,5 g ha-1), oxadiazon (875 g ha-1) e 2,4-D (698 g ha-1), além de um tratamento controle sem aplicação de herbicidas. As avaliações de fitointoxicação foram realizadas a cada 7 dias após a aplicação dos herbicidas (DAA) até o desaparecimento dos sintomas. A análise anatômica foliar desta espécie foi realizada coletando suas folhas ao 35o DAA. Avaliaram-se os caracteres quantitativos da quilha e da asa do limbo foliar de grama Batatais e os resultados foram submetidos à Análise de Agrupamento. Os caracteres morfológicos das gramas (caracteres biométricos), como a altura de planta e massa seca também foram avaliados. Os herbicidas bentazon, nicosulfuron, halosulfuron, oxadiazon e 2,4-D causaram injúrias sobre P. notatum, as quais dissiparam-se até os 35 DAA, exceto os sintomas causados pelo nicosulfuron. Aos 35 DAA o 2,4-D foi o único herbicida que não afetou a altura de plantas. Não foram observadas diferenças entre os tratamentos quanto à massa seca das plantas. A Análise de Agrupamento resultou na formação de dois grupos distintos, sendo que o primeiro grupo formou-se pelo tratamento controle, com os herbicidas bentazon, halosulfuron e 2,4-D; o segundo grupo foi representado pelos herbicidas nicosulfuron e oxadiazon. Os herbicidas que constituíram o segundo grupo foram os menos seletivos à espécie.

The aim of this work was to evaluate the selectivity of herbicides applied in post-emergence on Zoysia japonica Steud (Poaceae) and determine associations with the leaf anatomy of this grass. The experimental design was randomized blocks with four replications. The treatments were the application of the herbicides bentazon (720 g ha-1), nicosulfuron (50 g ha-1), halosulfuron (112.5 g ha-1), oxadiazon (875 g ha-1) and 2.4-D (698 g ha-1), plus a control treatment without herbicide application. Phytotoxicity was assessed every seven days after application (DAA) of the herbicides until the symptoms disappeared. Foliar anatomical analyses of the leaves in the collected grass were conducted until the 35th DAA. The quantitative characters of the keel and wing region of the blade of Z. japonica were assessed, as well as the biometric characters, which were submitted to an analysis of variance F test, and the averages were compared by Tukey's test at a probability of 5%. The values of the anatomical characters of the foliar blade were tested by cluster analysis. The application of herbicides did not negatively influence the height of the plants but did reduce their dry mass. Toxic symptoms disappeared after 21 DAA, with the only symptoms of injury observed in plants treated with the herbicides oxadiazon and nicosulfuron. In addition, the cluster analysis indicated the formation of a unique discriminatory group. Thus, the results show that the herbicides applied to Z. japonica were selective for the species.

The resistance of tomato plants (Solanum Lycopersicum L.) to M. incognita, M. javanica and M. arenaria, provided by the presence of Mi gene, does not include the species M. enterolobii (=M. mayaguensis).The aim of this study was to verify the anatomical changes caused by M. enterolobii in the root system of rootstocks from tomato plants with Mi resistance gene ('Magnet' and 'Helper M') and to compare these changes with those caused by M. javanica .The anatomical observations of roots were done with the aid of a light microscope and the most relevant aspects were photographed. Based on counts and measurements of the size of feeding sites and giant cells, the data Westerich, J.N.; Rodella, R.A.; Rosa, J.M.O.; Wilcken, S.R.S. Anatomical Changes Induced by Meloidogyne enterolobii (=M. mayaguensis) and Meloidogyne javanica in Tomato Plants Resistant to the Root-Knot Nematode. Summa Phytopathologica, v.38, n.3, p.192-197, 2012.

The resistance of tomato plants (Solanum Lycopersicum L.) to M. incognita, M. javanica and M. arenaria, provided by the presence of Mi gene, does not include the species M. enterolobii (=M. mayaguensis). The aim of this study was to verify the anatomical changes caused by M. enterolobii in the root system of rootstocks from tomato plants with Mi resistance gene ('Magnet' and 'Helper M') and to compare these changes with those caused by M. javanica. The anatomical observations of roots were done with the aid of a light microscope and the most relevant aspects were photographed. Based on counts and measurements of the size of feeding sites and giant cells, the data were analyzed by using the statistical method of Cluster Analysis. The emergence of nurse cells stimulated by M. enterolobii was observed for both tomato rootstocks between 10 and 17 days after inoculation (DAI). The number and the area of feeding sites and giant cells were smaller at 17 DAI than at 24 DAI. On the latter occasion (24 DAI), there were feeding sites established by the presence of several multinucleate nurse cells with thick cell walls and dense and granular cytoplasm. Vascular tissues were compressed and disorganized; there was also hypertrophy of cortical parenchyma cells. Roots inoculated with M. javanica did not show anatomical changes.

A velocidade de hidratação de sementes de soja pode ser afetada pela permeabilidade do tegumento devido a variações de espessura e composição. O objetivo no presente trabalho foi avaliar a relação entre a velocidade de hidratação e a espessura e o teor de lignina do tegumento de sementes de soja de diferentes cultivares e locais de produção. Sementes de soja de diferentes cultivares e localidades de produção, caracterizadas inicialmente quanto ao teor de água, massa de cem sementes, dano mecânico, germinação e condutividade elétrica, foram avaliadas quanto à velocidade de hidratação, ao teor de lignina do tegumento e às espessuras da camada paliçádica, hipoderme, parênquima lacunoso e total deste tecido de cobertura. O delineamento experimental foi o inteiramente casualizado e as médias foram comparadas pelo teste Tukey (P<0,05) e pelo teste de correlação linear simples (r). A velocidade de hidratação foi avaliada em esquema fatorial 4 x 8 (cultivar x tempo de hidratação), para cada localidade de produção, ajustando-se curvas de respostas. Concluiu-se que a velocidade de hidratação de sementes de soja é afetada pela cultivar e local de produção e que se relaciona significativamente com a espessura do parênquima lacunoso.