Maria Luiza Ribeiro Bastos da Silva

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.

Eficiência simbiótica de estirpes Hup+, Hup hr e Hup- de Bradyrhizobium japonicum e Bradyrhizobium elkanii em cultivares de caupi

The effectiveness of Bradyrhizobium strains with characteristics Hup+ (SR and USDA-110), Hup- (29W) and Huphr (SEMIA-587), was evaluated in cowpea (Vigna unguiculata L.), cultivars IPA-202, BR-3 and VITA-4. Results showed that nodulation in VITA-4 was superior, with a positive interaction when inoculated with strains SEMIA-587 and USDA-110. However, when comparing nodule efficiency, the combination IPA-202 x SEMIA-587 presented the highest nitrogenase activity, with a relative efficiency around 1.0. Nitrogenase activities were similar in plants inoculated with the strains SR and SEMIA-587, and higher, with strains USDA-110 and 29W. These results indicate that strains with Hup+ and Huphr were able to achieve higher enzymatic activities. Leghemoglobin (Lb) content detected in strains SR and USDA-110 was positively correlated to nitrogenase activity. However, correlations between Lb and nitrogenase activity were highly variable in nodules containing strain 29W-Hup-, indicating that imbalances in the nitrogenase system in the absence of hydrogenase may affect the flow of Lb to the bacteroids. Significant differences on the plant N content were found among the strains studied, but not among cultivars. Plant inoculated with Hup+ strains were more efficient to accumulate N, indicating that N-fixing systems retaining H2 may accumulate additional N in the host.

Caracterização morfológica e molecular de fungos micorrízicos arbusculares isolados de áreas de mineração de gesso, Araripina, PE, Brasil

Morphological and molecular characterization of arbuscular mycorrhizal fungi isolated from gypsum mining areas, Araripina, Pernambuco State, Brazil). The occurrence of arbuscular mycorrhizal fungi (AMF) in native (AN) and gypsum mining impacted (AI) areas in Araripina, Pernambuco State, Brazil, was determined using as trap cultures sorghum and peanut. The spores were morphologically characterized for identification at species level. DNA was extracted from spores and sequences of the ITS region used for molecular characterization. The molecular study confirmed the identification of three genera and four species (Funneliformis mosseae, Glomus sp., Glomus hoi, Claroideoglomus claroideum) that show ability to support stress conditions. Field work should be carried out to better understand the dynamics and functionality of these AMF species which could be selected for management programs in similar degraded areas.

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.