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Two phytopathogenic bacteria, MAFF 301380T and MAFF 301381, isolated from rot lesions of lettuce (Lactuca sativa L. var. capitata L.) in Japan, were characterized using a polyphasic approach. The cells were Gram-reaction-negative, aerobic, non-spore-forming, rod-shaped and motile with one to three polar flagella. Analysis of the 16S rRNA gene sequences showed that the strains belong to the genus Pseudomonas and are closely related to Pseudomonas cedrina subsp. cedrina CFML 96-198T (99.72 %), Pseudomonas cedrina subsp. fulgida P515/12T (99.65 %), Pseudomonas gessardii DSM 17152T (99.51 %), Pseudomonas synxantha DSM 18928T (99.44 %), Pseudomonas libanensis CIP 105460T (99.44 %) and Pseudomonas lactis DSM 29167T (99.44 %). The genomic DNA G+C content was 60.4 mol% and the major fatty acids consisted of summed feature 3 (C16 : 1 ω7c/C16 : 1 ω6c), C16 : 0 and summed feature 8 (C18 : 1 ω7c/C18 : 1 ω6c). Phylogenetic analysis using the rpoD gene sequences and phylogenomic analyses based on the whole genome sequences demonstrated that the strains are members of the Pseudomonas fluorescens subgroup but formed a monophyletic and robust clade separated from their closest relatives. The average nucleotide identity and digital DNA-DNA hybridization values between the strains and their closely related species were 88.65 % or less and 36.3 % or less, respectively. The strains could be distinguished from their closest relatives by phenotypic characteristics, pathogenicity towards lettuce and whole-cell MALDI-TOF MS profiles. The evidence presented in this study supports the classification of the strains as representing a novel Pseudomonas species, for which we propose the name Pseudomonas lactucae sp. nov., with the type strain MAFF 301380T (=ICMP 23838T).

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This study aimed to use different nitrogen fertilizer regimes to produce Butterhead lettuce with such large differences in nitrate content that they could be used as treatment and placebo to study the effect of inorganic nitrate on human health. Plants were grown under controlled conditions at 27/23 °C day/night with a relatively low photosynthetically active radiation (PAR) of 150 µmol m-2 s-1 for 14 h day-1 and nitrogen supplies ranging from 26 to 154 ppm of N as ammonium nitrate in the fertigation solution. This resulted in contrasting high (∼1078 mg nitrate 100 g-1 FW) or low (∼6 mg 100 g-1) nitrate contents in the leaves. Contents of carotenoids and chlorophylls in fresh weight did not differ significantly between the highest and the lowest N-supply levels. However, increased nitrogen supply reduced contents of phenolic compounds from 154 to 22 mg 100 g-1 FW, dry matter content from 8.9% to 4.6%, and fresh weight per plant from 108.52 to 47.57 g/plant FW (all P < 0.001). Thus, while fertilizer treatments can provide lettuce with substantially different nitrate contents, maintaining similar pigment contents (color), they also strongly influence the contents of phenolic acids and flavones.

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Na Amazônia a base da exploração comercial de olericolas é o reconhecimento de cultivares e/ou variedades que evidenciem melhor adaptabilidade para as condições edafoclimaticas locais, associados aos níveis de produtividade comercial em função do sistema de cultivo adotado. Neste sentido, o trabalho teve o objetivo de avaliar a variabilidade morfológica, qualidade e a produtividade entre cultivares de alface tipo americana, cultivadas a campo, em canteiros na presença e ausência de mulching orgânico, no período de estação seca da Amazônia central, estabelecendo-se um experimento no município de Presidente Figueiredo ­ AM. O delineamento experimental utilizado foi blocos ao acaso em esquema fatorial constituídos por 2 preparos de canteiro x 19 cultivares de alface americana, com quatro repetições. Os componentes avaliados foram; estabilidade morfológica; sanidade das plantas; matéria fresca comercial, diâmetro da cabeça comercial, altura das plantas, numero de folhas, comprimento do caule e estimativa da produtividade comercial Kg ha-1. O teste F (p<0,05) detectou diferenças significativas entre o fator correspondente as cultivares, e na interação apenas para sanidade, matéria fresca comercial, numero de folhas e comprimento do caule. Com exceção da estabilidade morfológica, no agrupamento das medias pelo teste Scott-Knott 5 % detectou-se diferença significativa para todas as características avaliadas entre as cultivares. As cultivares Gloriosa, Havassu, Ironwood, Kaiser e Winslon estabeleceram-se mais estáveis na formação de cabeças com melhores resultados agronômicos sobre as características avaliadas para as condições fitotécnicas e edafoclimaticas presentes neste ensaio.

In Amazon the exploration base commercial of vegetable crops is recognition of cultivars and / or varieties that show better adaptability to local conditions, associated with the levels of productivity commercial depending on the crop system. In this sense, the work aimed to evaluate the morphological stability, quality and productivity among cultivars crisphead lettuce, cultivated in seedbeds in the presence and absence of organic mulching, during the dry season in central Amazonia, stabilizing an experiment in municipality of Presidente Figueiredo - AM. The experimental design was a randomized block design in a factorial design consisting of 2 preparations of seedbeds x 19 cultivars of lettuce, with four replications. The components evaluated were; morphological variability; sanity of plants; the fresh materia commercial; commercial head diameter; plant height; number of leaves; stem length and estimated marketable yield kg ha-1. The F test (p <0.05) revealed significant differences the factor corresponding between cultivars and the interaction only for sanity, fresh commercial mass, leaves number and stem length. With the exception of morphological variation in the grouping of averages by the Scott-Knott test at 5 % significant difference was detected for all traits among cultivars. The cultivars; Gloriosa, Havassu, Ironwood, Kaiser and Winslon establish more stable to form heads with better results on agronomic characteristics evaluated for soil and parameters climatic in conditions gifts in this essay.

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