Foliar Area Research Articles

First Report of Powdery Mildew Caused by Golovinomyces sp. on Plantago australis in Brazil.

The plantain Plantago australis Lam. (Plantaginaceae) is a herbaceous species native to southern Brazil that is known for the analgesic, antibiotic, and anti-inflammatory properties of its leaf extracts (2). Powdery mildew was observed on wild P. australis plants in the cities of Tapejara, Jari, and Santa Maria (State of Rio Grande do Sul, Brazil) during the summer of 2011. Affected plants were more often observed in shaded areas. Signs included sparse to abundant white powdery masses of conidia and mycelium on pseudo-petioles and leaves, mostly on the adaxial surface. Severely affected plants (≥80% of foliar area affected) had small chlorotic leaves and reduced size compared to healthy ones. Mycelia were superficial and presented nipple-shaped appressoria. Conidiophores were often curved at the base, unbranched, cylindrical, 81 to 125 μm long (average 97.3 ± 14.9 μm) and composed of a cylindrical foot cell 52 to 73 μm long (average 65.4 ± 7.5 μm) and 9 to 14 μm wide (average 11.6 ± 1.5 μm) followed by one to two shorter cells 17 to 29 μm long (average 23.4 ± 3.6 μm). Conidia were produced in chains of up to eight cells, did not contain fibrosin bodies, ranged from ellipsoid-ovoid to subcylindrical, and measured 24 to 35 μm long (average 30.5 ± 3.7 μm) and 12 to 19 μm wide (average 15.8 ± 1.7 μm). Germ tubes were produced apically (reticuloidium type). Chasmothecia were not observed on sampled leaves. Genomic DNA was extracted from conidia, conidiophores, and mycelium and used to amplify the internal transcribed spacer (ITS) (ITS1-5.8s-ITS2) region using the ITS1 and ITS4 primers. The resulting sequence (558 bp) was deposited under accession number JX312220 in GenBank. Searches with the BLASTn algorithm revealed similarity of 100% with Golovinomyces orontii (Castagne) V.P. Heluta 1988 from Veronica arvensis L. (AB077652.1) (3), 99% with G. orontii from Galium spurium L. and Galium aparine L. (AB430818.1 and AB430813.1) (2) and 99% with G. sordidus (L. Junell) V.P. Heluta 1988 from P. lanceolata L. (AB077665.1) (3). Based on morphological characteristics and sequence analysis of the ITS region, the fungus was identified as belonging to Golovinomyces sp. To fulfill Koch's postulates, five cultivated plants of P. australis with four to five expanded leaves were inoculated by dusting conidia (10 to 15 conidia cm-2) on their leaves. Inoculated and non-inoculated control plants were kept in a greenhouse at 27 ± 5°C and relative humidity of 80 ± 15%. Powdery mildew symptoms identical to those of wild plants were observed 8 to 10 days after in inoculated plants. Although G. sordidus was previously reported on P. australis subsp. hirtella in Argentina and on several species of Plantago in others world regions (1), to our knowledge, Golovinomyces sp. has not been previously reported as a pathogen of P. australis in Brazil. Although the economic impact of the disease is limited, the reduction in plant size and leaves affects biomass production used in the extraction of pharmaceutical compounds.

Response of Eucalyptus (Eucalyptus urograndis) Plants at Different Doses of Glyphosate

The aim of this study was to evaluate the response of eucalyptus plants submitted to the application of glyphosate increasing rates. The doses 0.0, 3.6, 7.2, 18, 36, 72 and 180 g ha-1 of acid equivalent (ae) of glyphosate were applied on plants. At 7, 15, 22, 29, 36 and 42 days after application (DAA) was determined leaves relative chlorophyll content and quantum efficiency of photosystem II. At 22 and 42 DAA plant height and stem diameter were measured. At 42 DAA were determined the leaves dry mass, stem dry mass and foliar area. The height, diameter, leaves and stem dry masses and foliar area were converted to percentages, whereas the controls as 100%. These variables were fitted to the model described by Gauss equation. The data chlorophyll content and quantum efficiency of photosystem II were submitted to mean comparison, and when they differed, we performed the Tukey test at 5% probability. All the features presented here showed some hormetic effect promoted by reduced rates of glyphosate and the increments observed in these characteristics (when compared to control) ranged between 5.92 and 33.18% at 42 DAA. From average curve with height, diameter, leaves dry mass, stem dry mass and foliar area can be concluded that the increase averaged 12% on application of 16 g a.e. of glyphosate ha-1. For leaves chlorophyll content significant differences were observed only at 29 DAA, while for quantum efficiency of photosystem II significant differences were found only at 7 DAA.

Modelos para estimativa da área foliar da mangueira utilizando medidas lineares

Objetivou-se determinar os modelos que melhor descrevem a relação entre as dimensões lineares e a área foliar da mangueira, cultivar Tommy Atkins, além de estabelecer o fator de correção. A pesquisa foi conduzida na Fazenda Experimental da Universidade Federal Rural da Amazônia, na vila de Cuiarana, município de Salinópolis. Foram analisadas de 90 a 150 folhas, em 11 árvores de um campo experimental, determinando-se o comprimento e a largura máxima das folhas. A área foliar real foi determinada usando o integrador de área foliar "Area Meter" (AM 300). O fator de correção foi obtido pela divisão da área foliar real pela área foliar calculada. A área foliar foi também estimada por meio de modelos linear e não linear. Os modelos gerados apresentaram ótimo desempenho, com valores de R² entre 90 e 97%. O fator de correção de 0,71 pode ser utilizado para estimar a área foliar real da mangueira, multiplicado pelas medidas lineares. Os modelos que utilizaram o produto das dimensões como variável independente apresentaram valores de R² superiores aos que utilizaram apenas uma das dimensões, sendo o tipo cúbico o mais preciso.

Efecto del ácido salicílico y la nutrición mineral sobre la calidad de plántulas de chile habanero.

The objective of this study was to evaluate the effect of salicylic acid and N P K fertilization on the growth and mineral status of habanero pepper seedlings (Capsicum chinense Jacq.). The study was developed in Yucatan, Mexico in November 2008 and December 2009. Seedlings were exposed to four treatments: T1) without salicylic acid and fertilization; T2) application of 10-8 M salicylic acid; T3) application of 190 mg/l de NPK and T4) application of 10-8 M of salicylic acid + 190 mg/l of NPK. The quality of seedlings was evaluated by measuring growth characteristic of shoot and root. The content of N, P, K, Ca, Mg, Cu, Fe, Zn and Mn was analyzed in whole seedlings. The slenderness and the index of quality of Dickson were also considered. The results showed significant differences (P≤0.05) on shoot growth. Applications of fertilizer caused increase on shoot dry weight. Plant height, number of leaves, stem diameter, and foliar area were not significantly different between T3 and T4. Significant differences were observed on root dry weight, specific root length, root weight density and root length density. All variables except specific root length were significantly higher with the fertilizer treatment. The latest had the highest value in the treatment T4. Significant differences (P≤0.05) were observed in tissue mineral content. Seedlings treated with T3 showed the highest content of N, P, Ca, Mg and Mn. The content of K, Zn and Fe was not significantly different between T3 and T4. In conclusion, the application of salicylic acid favored seedling growth but it did not improve significantly the quality of habanero pepper seedlings.

Oviposition preference and larval development of the invasive moth Cydalima perspectalis on five European box‐tree varieties

AbstractThe box‐tree pyralid Cydalima perspectalis (Walker 1859) (Lepidoptera: Pyralidae), native to Eastern Asia, is a newly introduced species causing severe damage to box‐trees (Buxus sp.) in private and public gardens as well as in semi‐natural box‐tree forests in Central Europe. It is so far not known whether different box‐tree subspecies (or varieties) are similarly affected by this invasive moth. In a choice experiment offering branches of five different box‐tree varieties as oviposition sites, we found a preference of female moths for laying their egg clusters on the variety ‘Rotundifolia’, while other varieties were less frequently considered. The preference for ‘Rotundifolia’, the variety with the largest leaves in the tests, remained when intervariety differences in foliar area (mean leaf size × number of leaves) were taken into account. Feeding larvae on leaves of either of the five box‐tree varieties revealed a significant effect of the seasonal generation of C. perspectalis on the growth rate of individuals but no influence of the box‐tree variety. Larvae from the spring generation show the highest growth rate, those from the summer generation a moderate and those from the autumn generation the lowest growth rate. The moths used in the experiments may belong to the 10th to 12th generation present in Europe. The time elapsed since their introduction may be too short for an optimal adaptation to the partly novel diet encountered by the invasive moth.

INFLUENCE OF HYDRIC BALANCE ON ENVIRONMENTAL PHYTOINDICATION OF RUDERAL FRAGMENTS

The aim of this present work is to verify the action of the hydric balance on phyto-sociological and physic-ecological factors in plant from ruderal fragment. It was determined the leaf number (NF), dry weight of leaves (PSF), foliar area (AF) and the weight of the total dry substance (PMSt). With the values of AF and PMST, the growth analysis parameters had been calculated. These phyto-ecological factors are: index of foliar area (IAF), reason of the foliar area (RAF), absolute growth rate (TCA), production of dry substance rate (TPMS), relative growth rate (TCR), assimilating net rate (TAL). Also the phyto-sociological factors had been calculated: relative density (DR), absolute frequency (FA), relative frequency (FR), relative domain (DoR), importance value index (IVI) and relative importance (IR).In accordance with the hydric balance analysis in the region (Vassouras, Rio de Janeiro, 43° 07'' N/22° 08' S), it was observed that the analyzed locality has a period of drought that corresponds from May to September, when the temperature raises. The period of hydric excess is observed from October to January and in April, and in December, the summer time. The total annual average of the precipitation and the average temperature for the locality are, respectively, 1264,7 mm and 25,6° C. It has a hydric annual deficit of 30 mm and an excess of 372 mm.A cause that modifies the use of the LBC (folíolo-pecíolo angle class) in natural conditions is the environmental factors, as temperature, hydric deficit and nutritional state of the plant. Low wf had modified some morphologic parameters in ruderal plants, including the size and the total number of leaves in blossom. The reference value (r) was determined as 30 mm, based on comments on the leaves tissue formation and on growth curves. It is verified that the duration of plastocrono (p/r) was 0,61 per day and the rate of the leaves appearance in the launching is (r/p) 0,83 per day, for hydric excess in the plants under 0,12 deficit met p/r = 0,89 per day and r/p = day. Keywords: Hydric, Environmental Phytoindication, Ruderal

Eficiência de conversão da radiação fotossinteticamente ativa interceptada em fitomassa de mudas de eucalipto

A produção de fitomassa é uma função da eficiência de conversão da radiação solar fotossinteticamente ativa interceptada em fotoassimilados, variando conforme as condições em que as plantas são cultivadas. Assim, este trabalho teve como objetivo quantificar a eficiência de conversão da radiação solar fotossinteticamente ativa interceptada em fitomassa - εb - de mudas de Eucalyptus grandis W. Hill ex Maiden (eucalipto) quando submetidas a diferentes tamanhos de tubetes e densidades de plantas. Para tanto, foi conduzido um experimento, em delineamento de blocos ao acaso, para estudar a produção de mudas em dois tamanhos de tubetes (pequeno e médio) e duas densidades de plantas na bandeja (alta com 100% de ocupação da bandeja e média com 50%), em que foram determinados a radiação fotossinteticamente ativa interceptada (RFAi), o índice de área foliar e a fitomassa seca total das mudas. O volume do tubete não interferiu nos valores de eficiência, mas, sim, a densidade de plantas, pois o índice de área foliar é quem determina tal valor. A εb foi de 7,33 g.MJ-1 em tubete médio e pequeno em densidade alta e de 3,26 g.MJ-1 em tubete médio e pequeno em densidade média.

Produtividade e desenvolvimento de cultivares de repolho em função de doses de boro

A cultura do repolho é cultivada em áreas pequenas e necessita de muita mão de obra, sendo na maior parte conduzida pela agricultura familiar. Avaliou-se o efeito de doses de boro em diferentes cultivares de repolho na região oeste de Mato Grosso do Sul. O experimento foi conduzido na Universidade Estadual de Mato Grosso do Sul, Unidade Universitária de Aquidauana. O delineamento experimental utilizado foi de blocos casualizados no esquema fatorial 2 x 5, sendo duas cultivares e cinco doses de boro, com quatro repetições. Foram avaliadas as características: teores de boro foliar, área da planta, altura de planta, número de folhas externas, massa fresca de folhas externas, massa seca de folhas externas, altura da cabeça, diâmetro da cabeça, número de folhas internas, massa fresca de folhas internas, massa seca de folhas externas, classificação do peso da cabeça, compacidade e produção por hectare. A cultivar 60 Dias apresentou maiores valores nos componentes de produção e conseqüentemente maior produtividade. A aplicação de boro influencia linearmente nos teor de boro foliar, diâmetro de cabeça e número de folha interna. As doses de boro interferem na produtividade de repolho, sendo que na cultivar 60 Dias a dose máxima é de 7,2 kg ha-1 e para cultivar Chato de Quintal a dose mínima deve ser de 1,06 kg ha-1.

Influence of repeated canopy scorching on soil CO2 efflux

Forest ecosystems experience various disturbances that can affect belowground carbon cycling to different degrees. Here, we investigate if successive annual foliar scorching events will result in a large and rapid decline in soil CO2 efflux, similar to that observed in girdling studies. Using the fire-adapted longleaf pine (Pinus palustris Mill.) tree species, we experimentally manipulated foliar leaf area and thus, canopy photosynthesis, via foliar scorching over two consecutive growing seasons. We monitored the effect of scorching on soil CO2 efflux and fine root production, mortality, standing crop, and nitrogen (N) and non-structural carbohydrate (i.e. sugar and starch) concentrations. Despite an immediate 80% reduction in foliar leaf area and sap flow rates from the scorch treatment, there was no effect on soil CO2 efflux in either year. Likewise, the cumulative soil CO2 flux after two scorch treatments remained comparable to that of the control treatment, even after assuming a 100% decline in the autotrophic component for the month following the two scorching events. Fine root standing crop was not diminished by scorching because both fine root production and mortality increased commensurately in the scorch treatment. Fine root N and sugar concentrations were not diminished by scorching, but starch concentrations of 5th order roots decreased after the second scorching treatment, presumably because starch was mobilized from larger roots to maintain more metabolically active 1st order roots. The lack of response observed in soil CO2 efflux following successive canopy scorches differs from the response often observed after girdling and suggests that the carbohydrate reserves of longleaf pine trees are sufficient to maintain root metabolism for extended periods even after an extreme canopy perturbation. We propose that tree species in ecosystems that experience frequent disturbance may allocate more carbon to storage than those in less disturbed ecosystems, and as a result are more resilient to disturbances that affect photosynthate supply. Such species should be capable of maintaining belowground autotrophic respiration during periods of minimal or nonexistent carbon assimilation.

Mapping and candidate gene identification of loci determining tolerance to greenbug (Schizaphis graminum, Rondani) in barley

Greenbug is one of the most aggressive pests of barley and wheat. In Argentina, yield losses of wheat, barley, oat and sorghum crops caused by greenbug are chronic and at times severe. Since Marker Assisted selection for greenbug resistance genes in barley is very limited, the purpose of the current study was to map greenbug resistance genes in doubled haploid (DH) lines and to identify candidate genes. A set of DH lines of the Oregon-Wolfe Barley (OWB) mapping population derived from the cross between OWBDOM and OWBREC and both parental lines were screened for tolerance to greenbug. There was significant variation among the DH lines in foliar area (FA), dry weight (DW) and chlorophyll contents (Ch) between infested and control DH lines. Three main QTLs were identified. These QTLs explained 82 % of the FA, 80 % of DW and 58 % of Ch variability of infested plants. The initial and final FA and DW of controls and final DW of infested plants were associated with the same molecular markers on chromosome 2H (Vrs1, BmAc0144f, GBR259, GBS705). The final FA of infested plants was significantly linked to molecular markers on chromosome 5H (GBRO986, GBR518, GBM1483, GBR1082). The positive alleles were provided by OWBDOM. The content of chlorophyll of infested plants was associated with the marker loci Ris44, GBR1608, GBR1637N and GBS0785 on chromosome 7H, with the positive alleles provided by OWBREC. Both parents contributed to different tolerance traits. The QTLs found in this population are new greenbug resistance loci. A sequence homology search was performed to derive the putative function of the genes linked to the QTLs.

Ação protetora, residual, curativa e anti-esporulante de fungicidas no controle da requeima e da pinta preta da batata em condições controladas

A ação de fungicidas em diferentes fases do processo infeccioso da requeima (Phytophthora infestans) e da pinta preta (Alternaria solani) da batata foi estudada em condições de casa-de-vegetação e laboratório. A ação protetora e residual foi avaliada através de inoculações realizadas com os respectivos patógenos a 1, 3, 6, 9, 12 e 15 dias após a pulverização (DAP). Para avaliar a ação curativa, os fungicidas foram aplicados 1, 12, 24 e 48 horas após a inoculação (HAI) para requeima e 1, 24, 48 e 72 HAI para a pinta preta. As ações preventiva, residual e curativa foram avaliadas com base na porcentagem de área foliar afetada e a ação anti-esporulante através da contagem de esporângios e conídios. Todos os fungicidas promoveram elevada proteção contra a requeima e a pinta preta. Os fungicidas sistêmicos apresentaram redução de controle a partir dos 12 DAP, enquanto que os fungicidas translaminares e mesostêmicos a partir dos 9 DAP. Quanto à ação curativa e anti esporulante, destacaram-se principalmente os fungicidas sistêmicos aplicados até as 24 horas após a inoculação (HAI). Fungicidas translaminares e mesostêmicos foram capazes de inibir a requeima quando aplicados até 12 HAI. Os fungicidas de contato destacaram-se apenas para ação protetora.

Initial Growth of Peanut Cultivars at Presence of Different Sugarcane Straw Quantities

This work was carried out to evaluate the effect of sugarcane straw on plants emergence and some characteristics of initial growth of peanut plants in boxes with soil as substrate. The treatments constituted by straw quantities of: 0, 4, 8, 12, 16 and 20 t ha-1 and the five cultivars tested were IAC 213, IAC 503, IAC 505, IAC 886 and IAC Tatu ST. The experiment was arranged in a completely randomized design, in a factorial arrangement of 6 x 5 with four replications. At 30 days after sowing were evaluated chlorophyll content, height, emergence of plants, number of leaves, total foliar area, foliar area per plant, leaf, stem, aerial part total and per plant dry mass. Data obtained were submitted to F in variance analysis test and means were compared with Tukey at p>0.05. The same data were padronized and analyzed by hierarchical cluster analysis utilizing as the similarity coefficient the simple Euclidian distance and as linkage method the Ward Method. The straw did not affect the cultivars growth studied and the straight cultivar IAC Tatu ST had the major initial growth if compared to the other.

Mapping resistance genes conferring tolerance to RWA (Diuraphis noxia) in barley (Hordeum vulgare)

The Russian wheat aphid (RWA) is one of the most aggressive pests of barley and wheat. The outbreak of RWA occurred in Argentina in 2008 caused serious damage to barley cultivars. The most effective and sustainable method of RWA control is to identify new resistance genes. The purpose of the current research was to map RWA resistance genes in a set of double haploid (DH) lines of the Oregon-Wolfe Barley (OWB) mapping population derived from the cross between OWBDOM and OWBREC. The DH and both parental lines were screened for antixenosis, tolerance and antibiosis to RWA. There was significant variation among the DH lines in most of the traits studied. However, only tolerance resulted in significant quantitative trait loci (QTLs) associated with the molecular markers. Two main QTLs were identified. These explained 90 and 79 % of the variability of foliar area and chlorophyll content, respectively, of infested and control plants. The initial and final foliar area and the variation in foliar area were associated with the same molecular markers on chromosome 2H (BmAc0125, Vrs1, BmAc0144f and BmAg0113e). The positive alleles were provided by OWBDOM. The content of chlorophyll was associated with the marker loci WMC1E8, MWG912, ABC261, MWG2028 and Blp on chromosome 1H, with the positive alleles provided by OWBREC. Both parents contributed to different tolerance traits, with foliar area and chlorophyll content remaining as the plant traits most affected by aphid feeding. The QTLs found in this population are new RWA resistance loci. A sequence homology search was performed to derive the putative function of the genes linked to the QTLs.

Parameters Symptomatic for Boron Toxicity in Leaves of Tomato Plants

The incidence of boron (B) toxicity has risen in areas of intensive agriculture close to the Mediterranean sea. The objective of this research was to study the how B toxicity (0.5 and 2 mM B) affects the time course of different indicators of abiotic stress in leaves of two tomato genotypes having different sensitivity to B toxicity (cv. Kosaco and cv. Josefina). Under the treatments of 0.5 and 2 mM B, the tomato plants showed a loss of biomass and foliar area. At the same time, in the leaves of both cultivars, the B concentration increased rapidly from the first day of the experiment. These results were more pronounced in the cv. Josefina, indicating greater sensitivity than in cv. Kosaco with respect to excessive B in the environment. The levels of O2 •− and anthocyanins presented a higher correlation coefficient (r>0.9) than did the levels of B in the leaf, followed by other indicators of stress, such as GPX, chlorophyll b and proline (r>0.8). Our results indicate that these parameters could be used to evaluate the stress level as well as to develop models that could help prevent the damage inflicted by B toxicity in tomato plants.

QUANTIFYING YIELD LOSS OF AUBERGINE (SOLANUM MELONGENA L.) INDUCED BY LEAF AREA REDUCTION

The foliar area loss is a typical damage in crops caused by fungus, insects or hailstorm. A lot of studies have been carried out to describe the effect of defoliation in the main herbaceous and woody crops. The results of two trials carried out in Navarra (Spain) in 2007 to determine the effects of different levels of defoliation in several phenological stages in aubergine plants are described in this work. In a randomly split-plot design with four replications, four levels of defoliation were applied: control, slight, moderate and heavy, at six phenological stages of aubergine plants var Nilo (Rijk Zwaan). Defoliation was made by means of a jet of water under pressure in one trial and, by means of scissors in the other one. Fruits were harvested on three occasions and classified as marketable and unmarketable yield and were weighed. The BBCH stages 71 (the first fruit reaches the typical size) and 86 (60% of fruits reach the typical size, shape and colour) were the most sensitive stages for water defoliation and scissor defoliation respectively. These experimental results were used to obtain regression equations in which the percentage of yield reduction is calculated in relation with the stage and the percentage of defoliation. These equations were plotted and maximum loss of 77% in defoliation by scissor and 64% in defoliation by water were observed for 100% of defoliation. These equations can be used to improve simulation patterns of the aubergine growth in case of foliar damages caused by fungus, insect attacks or hailstorm.

Inferring changes in foliar mass and area from foliage cover: A mechanistic model

AbstractMeasuring foliar area or mass directly is destructive, and precludes long‐term, repeated observations of individual trees as they suffer or recover from foliar damage. Instead, foliage cover indices are often used as a proxy for foliar mass. Patterns of fluctuations in foliage cover indices can be used to infer qualitative changes in canopy health. However, foliage cover is not necessarily linearly related to foliar area or mass, and this may confound the detection of significant foliar damage, and comparisons of herbivore browse impacts between individual trees, tree species or sites. I derived a mechanistic model to quantify the relationship between foliar area or mass and foliage cover measured as the proportion of sky occluded by leaves. This one parameter model is close to linear for single‐tiered trees, but increasingly non‐linear for multi‐tiered trees. I compared the non‐linear model to a linear model using foliage cover data from an artificial defoliation experiment on two single‐tiered, sub‐canopy species and from simulated photographic images of single‐ and multi‐tiered canopies. The non‐linear model had lower errors than the linear model, and errors did not increase with foliage density (leaf area per unit area), variation (of leaf sizes within and between canopies) or leaf geometry. The non‐linear model can be easily parameterized from relatively low‐cost observations of foliage cover, independently of empirical measurements of foliar area or mass, and is applicable to a wide range of tree species. It should therefore help managers quantify how changes in foliage cover due to natural fluctuations or foliar damage affect foliar area and mass, and can be used to quantify parameters for models of browse impacts in mixed forest.

Sensibilidade de cultivares de mandioca ao herbicida mesotrione

Unsuitable weed management is one of the main factors responsible for low mean yield of cassava (Manihot esculenta Crantz) in Brazil. In this crop, mechanical weed control is the most commonly used, due to the lack of registered herbicides for cassava crop. In the search for alternatives to this problem, this work aimed to evaluate the tolerance level of cassavas cultivars to mesotrione herbicide applied in post emergence. A experiment was conducted, in green house conditions, in randomized blocks with four replications. A factorial scheme 5x5 was adopted, consisting of the combination of five dosages of mesotrione herbicides and five cassava cultivars. Intoxication of cassava plants, height, stem diameter and number of leaves of plants were evaluated weekly and 35 days after application (DAA) plants were harvested for determining dry matter and leaf area.n. The highest values for visual intoxication were observed at 14 and 28 days after the herbicide application (DAA) and caused by the highest doses of mesotrione herbicide. These symptoms consisted of whiteness in new leaves. At 35 days, plants showed signals of recovery, mainly due the sprout of new leaves. The herbicide did not affected the height, stem diameter, number of leaves, foliar area and dry matter accumulation of leaves, stems, roots and in total characteristics, in any of the evaluated doses. This is an evidence of cassava cultivars tolerance to mesotrione herbicide.

Consórcio de manjericão (Ocimum basilicum L.) e alface sob dois arranjos de plantas

Ocimum basilicum L. (Lamiaceae) é comercialmente utilizada como aromatizante ou condimento preparado com suas folhas verdes e aromáticas, que podem ser usadas frescas ou secas. O objetivo deste trabalho foi avaliar a produção de biomassa de manjericão sob duas ou três fileiras no canteiro, consorciado ou não com alface. O manjericão e a alface foram alocados no campo em experimento conjunto, sendo constituídos cinco tratamentos da seguinte forma: duas fileiras solteiras de manjericão (M2) espaçadas de 0,50 m; três fileiras solteiras de manjericão espaçadas de 0,33 m (M3); quatro fileiras solteiras de alface espaçadas de 0,25 m (A4); duas fileiras solteiras de manjericão consorciadas com quatro fileiras de alface (M2A4) e três fileiras de manjericão consorciada com quatro fileiras de alface (M3A4). O delineamento utilizado foi em blocos casualizados, com oito repetições. As plantas de alface foram colhidas aos 48 dias após o transplantio e as de manjericão, em duas épocas, aos 96 e 113 dias após o transplantio (DAT). O consórcio não influenciou as áreas foliares nem as produções de folhas ou inflorescências do manjericão nem de cabeças comerciais ou não-comerciais da alface. No entanto, quanto ao arranjo de plantas, na segunda época de colheita, as plantas de manjericão cultivadas sob duas fileiras tiveram maior área foliar (2.076,99 cm² planta-1) e maior massa fresca de folhas (5.012,53 kg ha-1). Considerando-se que os valores da Razão de Área Equivalente - RAE na primeira e segunda colheita do manjericão foram maiores que 1,0, conclui-se que o consórcio manjericão com alface é viável. Recomenda-se o arranjo de três fileiras de manjericão alternadas com quatro fileiras de alface, e colheita aos 96 DAT, por ter tido RAE de 2,01.

Relative Disease Susceptibility of Cultivated Varieties of Potato to Different Isolates of Phytophthora Infestans

ABSTRACT Late blight, caused by the Oomycete pathogen Phytophthora infestans, continues to be the most devastating and economically important disease affecting potato crops worldwide. Recent geographical migrations of the pathogen have displaced the ‘old’ US-1 clonal lineage with ‘new’, genotypically distinct, lineages. These new genotypes have shown increased pathogenic fitness and diverse environmental requirements. Interactions between two different isolates of the US-8 race and three potato (Solanum tuberosum) cultivars were analyzed through in planta infection, under controlled laboratory conditions. Disease development over time was rated for each experimental unit by determining incubation period, foliar lesion area and relative number of leaves displaying necrosis. Difference in incubation period between isolates was nearly significant in Russet Burbank, with disease symptoms presenting much later for replicates infected with PSUPotb. No significant difference was seen in incubation period between isolates in cv. Kennebec or cv. Red Norland, with the shortest incubation period occurring for isolate NC092ba in Kennebec. Incubation period did not differ for isolate NC092ba across cultivars. Isolate PSUPotb had a longer incubation period in Russet Burbank than in the other two cultivars. Data suggest, therefore, that differential pathogenicity between the US-8 isolates exists in at least one cultivar. Cultivar susceptibility was also variable. As suggested in previous studies, it was found that cv. Kennebec was least susceptible to either isolate. Confirmation of pathogen presence in infected leaf tissue was successfully obtained using previously developed P. infestans specific primers in a standard Polymerase Chain Reaction (PCR) assay.

Forest microhabitats differentially influence seedling phenology of two co‐existing Mediterranean oak species

AbstractQuestionHow do forest microhabitats impact seasonal microclimate conditions and phenological seedling strategies in two co‐occurring Mediterranean Quercus species with different leaf habits?LocationPinus halepensis woodlands, Provence, SE France.MethodsNinety sets of three acorns of Quercus ilex (evergreen) or Quercus pubescens (winter‐deciduous) were sown under various P. halepensis canopy cover conditions. Canopy cover and litter depth were measured at each sowing point, and soil moisture and temperature were measured twice monthly. Seedling phenology and aerial development were monitored during the second growing season under different microhabitats.ResultsDuring rainy periods, soil moisture was higher under open canopy and thinner litter layers, whereas during summer drought soil moisture was higher under dense canopy and thicker litter layers. Quercus pubescens seedlings had higher growth activity than Q. ilex before summer drought, whereas the pattern reversed during autumnal growth. Dense canopy cover strongly delayed budburst and decreased foliar development in Q. pubescens, which was more affected than Q. ilex. Depending on species phenology, litter thickness can influence height growth of flushes during early summer.ConclusionsQuercus pubescens has a phenological strategy to allow development of maximal foliar area before summer drought, a typical growth strategy of Mediterranean winter‐deciduous species. In contrast, later phenological activity of evergreen Q. ilex enables it to cope with the dry period and capitalize on autumnal precipitation events. Dense cover acts as shelter in the dry season but can reduce soil moisture during wetter seasons. In contrast to Q. ilex, Q. pubescens appeared strongly dependent on canopy cover, suggesting that Q. ilex has a larger regeneration niche in Aleppo pine woodlands. In the context of global change, this ‘microhabitat effect’ on species‐specific phenological strategy underlines the need to consider effects of local environmental conditions on regenerating species.