No abstract

Grasses such as sugarcane (Saccharum spp.), maize (Zea mays L.) and sorghum (Sorghum bicolor L. Moench) with C4 photosynthetic system are important crops that can host endophytic bacteria capable for biological nitrogen fixation (BNF). However, fixation measurements have yielded conflicting results. We determined BNF of five sugarcane and two sorghum varieties, maize and Guinea (Panicum maximum Jacq), elephant (Pennisetum purpureum Schum) and buffel (Cenchrus ciliaris L.) grasses in a pot experiment, using the 15 N natural abundance technique, with a soil naturally rich in 15 N (δ 15 N > 16 ‰) and two reference species (castor bean, Ricinus communis L., and cotton, Gossypium hirsutum L.) that absorb only N from the soil (average δ 15 N = 9.2 ‰). The initial results showed that no fixation occurred in elephant and buffel grasses. Sorghum, maize, Guinea grass and four sugarcane varieties had δ 15 N signals significantly lower than both reference species, indicating that they absorbed N from the atmosphere (δ 15 N = 0 ‰). The differences in signals from the reference species translates into proportions of plant N content originating from BNF varied from 12.8 to 19.4 % for sugarcane, 22.4% for maize, 20.9% for Guinea grass, and 24.7 to 31.2 % for sorghum. Nitrogen fixation by these species represents a potential of great fertilizer economy and high yields in low input agriculture.

O objetivo do trabalho foi avaliar a variabilidade de cultivares de coqueiro anão para caracteres morfológicos nos tabuleiros costeiros do Norte de Sergipe. O delineamento experimental utilizado foi em blocos casualizados, com seis cultivares de coqueiro anão, quatro blocos, sendo 16 plantas úteis/parcela. O experimento foi desenvolvido desde 1997, na Fazenda Agreste em Neópolis (SE). As cultivares Anão vermelho do Brasil de Gramame (AVBrG), da Malásia (AVM) e de Camarões (AVC), Anão amarelo do Brasil de Gramame (AABrG) e da Malásia (AAM) e o Anão Verde do Brasil de Jiqui (AVeBrJ). Para cada característica avaliada trimestralmente de 2001 a 2004, foi realizada análise de variância e estimados os componentes de variação fenotípica, genética e ambiental. Existe variabilidade entre os anões para as características: número de folhas vivas (NFV) e emitidas (NFE), circunferência do estipe (CircE), comprimento do estipe (CE), número de inflorescências emitidas (NIE) e número de flores femininas por inflorescência (NFFI). O AVC e o AVeBrJ apresentaram menores CE que os demais, característica importante por redução do porte do coqueiro. O anão amarelo da malásia (AAM) foi superior aos AVeBrJ, AVM e AVC quanto ao NFE. O AVM foi superior aos AAM, AABrG, AVeBrJ e AVC quanto à CircE. O AVC apresentou comportamento inferior aos demais para NFV, NFE, CircE e NIE, sendo semelhante a eles para NFFI. O AVeBrJ foi superior ao AAM, AVBrG e AVM quanto à NFFI.

No abstract

Some forage species, such as pangolão grass (Digitaria eriantha Steud. cv. Survenola), are resilient in tropical semiarid regions. A possible reason for this is the presence of endophytic and rhizospheric microorganisms. Thus, this study evaluated the diversity of associative bacteria in pangolão grass. Bacteria associated with the roots, culm, leaves, and rhizospheric soil were isolated and characterized in three municipalities of Pernambuco, Brazil. An initial phenotypic characterization was followed by a genotypic assessment by based repetitive extragenic palindromic-polymerase chain reaction (BOX-PCR) and partial sequencing of the 16S rRNA gene. We obtained 325 phenotypically-characterized isolates grouped into 243 strains with 100% similarity by BOX-PCR. The most diverse sampling environment was Araripina, and all factors affected bacterial diversity. There were 135 groups with 90% similarity, that were represented by a single strain each for sequencing. Among the sequenced strains, 118 showed 96.84-99.9% similarity with previously described strains, whereas 17 could not be identified. The following 18 genera were identified from three phyla, five classes, seven orders, and 13 families: Achromobacter,