Maria do Carmo Catanho Pereira de Lyra

Efetividade da inoculação com rizóbio e fungos micorrízicos arbusculares em mudas de sabiá submetidas a diferentes níveis de fósforo

In order to optimize Mimosa caesalpiniifolia Benth seedlings production, an experiment was carried out to evaluate the inoculation with both arbuscular mycorrhizal fungi (AMF) and Rhizobium. Treatments, arranged in a factorial scheme, consisted of presence or absence of Rhizobium, and of AMF (a mixture of Glomus etunicatum, Acaulospora morrowae and A. longula), with three P levels (equivalent to 0, 20 and 40 kg/ha of P2O5), applied as triple superphosphate. The P application, in the absence or in the presence of AMF inoculation, did not enhance plant development, while the seedlings which received the double inoculation presented significant values on growth, height, leaf area, nitrogenase activity and others analyzed parameters, regardless of the P level. Mimosa caesalpiniifolia nodulation was enhanced by the inoculation with AMF, since plants which received Rhizobium alone showed significantly lower nodulation values than the ones which received both inoculations. There was an increase of the mycorrhizal and a decrease of the esporulation in the presence of Rhizobium.

Distinct bacterial communities across a gradient of vegetation from a preserved Brazilian Cerrado

The Cerrado biome in the Sete Cidades National Park, an Ecological Reserve in Northeastern Brazil, has conserved its native biodiversity and presents a variety of plants found in other savannas in Brazil. Despite this finding the soil microbial diversity and community structure are poorly understood. Therefore, we described soil bacterial diversity and distribution along a savanna vegetation gradient taking into account the prevailing environmental factors. The bacterial composition was retrieved by sequencing a fragment of the 16S ribosomal RNA gene. The bacterial operational taxonomic units (OTUs) were assigned to 37 different phyla, 96 classes, and 83 genera. At the phylum level, a core comprised by Proteobacteria, Acidobacteria, Actinobacteria, Firmicutes, Verrucomicrobia and Planctomycetes, was detected in all areas of Cerrado. ‘Cerrado stricto sensu’ and ‘Cerradao’ share more similarities between edaphic properties and vegetation and also present more similar bacterial communities, while ‘Floresta decidual’ and ‘Campo graminoide’ show the largest environmental differences and also more distinct bacterial communities. Proteobacteria (26%), Acidobacteria (21%) and Actinobacteria (21%) were the most abundant phyla within the four areas. All the samples present similar bacteria richness (alpha diversity) and the observed differences among them (beta diversity) were more related to the abundance of specific taxon OTUs compared to their presence or absence. Total organic C, N and P are the main abiotic factors structuring the bacterial communities. In summary, our findings show the bacterial community structure was clearly different across the Cerrado gradient, but that these environments share a bacterial phylum-core comprising Proteobacteria, Acidobacteria, Actinobacteria, Verrucomicrobia and Planctomycetes with other Brazilian savannas.

Fungal diversity in soils across a gradient of preserved Brazilian Cerrado

The preserved Cerrado from Northeastern Brazil presents different physicochemical properties and plant diversity, which can influence the fungal communities. Therefore, we evaluated the fungal diversity in preserved sites, at Sete Cidades National Park, across a gradient of vegetation that included Campo graminoide, Cerrado stricto sensu, Cerradao, and Floresta decidual. Of all of the operational taxonomic units (OTUs) obtained, the Floresta decidual presented the highest richness. Ascomycota were the most abundant phylum (45%), followed by Basidiomycota (32%). Basal fungi and other phyla accounted for 23% of the total dataset. Agaricomycetes, Eurotiomycetes, Lecanoromycetes, Basidiobolus, Dothideomycetes, and Taphrinomycetes were the most abundant classes of fungi found across the gradient of Cerrado vegetation. In conclusion, our study suggests that the Brazilian Cerrado from Sete Cidades National Park presents a high fungal diversity and includes sources of new fungal species for biotechnological purposes.

Nitrate levels and stages of growth in hypernodulating mutants of Lupinus albus. I. N2 fixation potential

This work aimed to evaluate physiological parameters, nodulation response and N2 fixation rate in mutants of Lupinus albus in comparison with the standard Multolupa cultivar. Two nitrate levels (0 and 5mM) and two evaluation periods (7 and 10 weeks) were used. Significant differences were observed among genotypes, in relation to fresh nodule weight, nitrate levels and growth stages. The overall average for nitrate level differed between them where 5mM severely inhibited the number of nodules, reaching a 49.5% reduction in relation to treatment without nitrate. There were no behaviour differences among genotypes, nor among evaluation periods. Although the level of nitrate did not influence the production of shoot dry matter in relation to the average among levels applied, the L-135 genotype, being an inefficient mutant, reached very low values. There were no significant differences in electron allocation coefficient (EAC) among nitrate levels, nor among genotypes studied. However, the evaluation periods revealed differences, where the EAC for the seventh week had a higher value than that for the tenth week, when a 5mM aplication was evaluated. The N2 fixation rate (N2 FIX) showed the existence of the nitrate interference in fixation, given that the application of 5mM severely reduced. However, there were no differences among the genotypes and it was noted that the fixation rate was much higher in those that received nitrate. The L-88 and L-62 genotypes were the ones that have shown best adaptability in this experiment, thus being able to be recommended for new studies with higher nitrate levels and different evaluation periods. The nitrate (5mM) interferes in the nitrogen fixation rate, given that all the genotypes were affected by the level applied.

Archaea diversity in vegetation gradients from the Brazilian Cerrado

We used 16S rRNA sequencing to assess the archaeal communities across a gradient of Cerrado. The archaeal communities differed across the gradient. Crenarcheota was the most abundant phyla, with Nitrosphaerales and NRPJ as the predominant classes. Euryachaeota was also found across the Cerrado gradient, including the classes Metanocellales and Methanomassiliicoccaceae.

Characterization of Metarhizium anisopliae using amplifed ribossomal DNA restriction analysis (ARDRA) and internal transcribed spacer (ITS) sequence analysis

Molecular methods have revolutionized systematic entomology in the genus Metarhizium . In Brazil, the importance of these entomopathogenic fungi in agriculture is critical to the control of the sugar cane spittlebug ( Mahanarva posticata ) ( Homoptera: Cercopidae ). Other important factors for the selection of isolates of Metarhizium anisopliae for use in the biological control of particular pests are virulence, reproductive characteristics and the media of artificial cultures. In addition, the genetic variability of these entomopathogenic fungi indicates a great potential for pest control and a lack of a link between isolates from specific host sites and fungal virulence. We studied five Metarhizium hosts including the sugar cane spittlebug (IPA213, IPA215, IPA219 and IPA216) and the grasshopper (IPA217). It is noteworthy that these five isolates are used as biological control for growing sugar cane on an industrial scale for the Brazilian Northeast. Hence, the importance to genetically characterize these isolates of Metarhizium cannot be over emphasized. Amplifed ribossomal DNA restriction analysis (ARDRA) did not differentiate any of the isolates that were studied following digestion with three endonuclease namely; HindIII, HinfI and HpaI . The data that were generated using ITS1 and ITS4 markers revealed that although these isolates infect the same host, they are genetically distinct perhaps due to the unknown origin of the hosts. However, the isolate IPA217, which was isolated from the grasshopper, did not behave differently from the others. These results show that the M. anisopliae complex is monophyletic and it was concluded that the use of markers and morphological studies yielded results that may corroborate the idea that investigation of the phenotypic and molecular characteristics of this genus may indentify a new species of Metarhizium . Key words : Cordyceps brittebankisoides, genetic identity, ITS1, ITS4, phylogeny, sugar cane spittlebug.

Nitrate levels and stages of growth in hypernodulating mutants of Lupinus albus. II. Enzymatic activity and transport of N in the xylem sap

O estudo enzimatico e o transporte de N na seiva do xilema foi realizado visando observar a influencia de diferentes niveis de nitrato e estagios de crescimento da planta em mutantes tratadas quimicamente. Varios estresses induzem a reducao no crescimento da planta da qual resulta na acumulacao de aminoacidos livres, amidas ou ureidos, tanto na parte aerea como nas raizes e nodulos. A atividade de enzimas e decisiva em evitar produtos inibidores da nitrogenase pelo amonio, porem poucas sao as informacoes deste mecanismo com o qual o xilema carrega estes produtos, em compensacao, este processo, pode ser a chave da funcao em evitar acumulacao de aminoacidos nas celulas dos nodulos infectados. O comportamento das enzimas nitrato redutase (NR), fosfoenolpiruvato carboxilase (PEPC), glutamina sintetase (GS) e dos compostos nitrogenados derivados da fixacao como: N-a-amino, N-ureidos e N-amida em genotipos mutados foi observado. A atividade da enzima nitrato redutase foi altamente inflenciada pela aplicacao de nitrato apresentando valores bastante superiores em relacao a nao aplicacao do nitrato, independentemente dos genotipos, sendo que o melhor periodo de avaliacao foi na decima semana. O genotipo L-62, com caracteriticas de resistencia ao nitrato, mostrou de forma bem evidenciada que a enzima PEPC e inibida pela presenca de nitrato. O genotipo L-135 (nod- fix-) apresentou atividade da GS extremamente baixo, mostrando desta forma que a GS e uma enzima altamente correlacionada com a fixacao. Em relacao ao melhor estagio de crescimento para a GS, o Lupinus albus, deve ser avaliado na setima semana.