On-farm assessment of eucalypt yield gaps — a case study for the producing areas of the state of Minas Gerais,Brazil

International Journal of Biometeorology - The concept of yield gaps provides a basis for identifying the main sources of production losses, caused by water or management deficiencies, which may...     

Tiny treefrogs in the Pleistocene: Phylogeography of Dendropsophus oliveirai in the Atlantic Forest and associated enclaves in northeastern Brazil

Wet and dry cyclical periods through the Pleistocene have been suggested as drivers of isolation and, consequently, divergence and expansions of populations associated with forest environments in the Neotropics. In northeastern Brazil, forests patches restricted to high altitudes led to the formation of regionally distinct ecosystems, known as “Atlantic Forest enclaves” or “brejos de altitude.” Herein, we investigated the population history of the treefrog Dendropsophus oliveirai, a species associated with the Atlantic Forest and areas of enclaves in the Northeast region of the Brazil. We obtained sequences for one mitochondrial and two nuclear loci of 50 samples from 16 localities to investigate the population structure and demographic history across northeastern Atlantic Forest enclaves. Our data revealed that D. oliveirai exhibits three mtDNA haplogroups: low and highlands above the São Francisco River; low and highlands between Chapada Diamantina enclaves and northern populations of coastal Bahia and Sergipe States; lowlands below the Contas River. Divergence times estimates revealed that population splits occurred during the Pleistocene. Our data recovered low genetic differentiation between enclaves and lowland populations north and south of the São Francisco River, which supports a scenario of recent contact and repeated recolonization of enclaves by lowland populations during the humid Pleistocene phases. Species tree, and temporal and spatial population structures may indicate that D. oliveirai is actually a species complex.     

Epilithic biofilms provide large amounts of nitrogen to tropical mountain landscapes

We show that epilithic biofilms are a relevant nitrogen (N) source in a rocky mountain range in Brazil. During different seasons, we quantified nitrate, ammonium, dissolved organic N (DON) and total dissolved N (TDN) leached by a simulated short rain event. We quantified the epilithic autotrophic biomass by taxonomic groups and its correlation with leached N. We hypothesized that leached N would be correlated to heterocystous cyanobacteria biomass since they are more efficient N₂ fixers. We estimated a landscape N supply of 8.5 kg.ha⁻¹.year⁻¹ considering the mean precipitation in the region. TDN in leachate was mainly composed of DON (83.8% ± 22%), followed by nitrate (12.1% ± 3%) and ammonium (5% ± 5%). The autotrophic epilithic community was mainly composed of non-heterocystous (Gloeocapsopsis) and heterocystous cyanobacteria (Scytonema and Stigonema), except for a site more commonly affected by fire events that showed a dominance of Chlorophyta. Biogeochemical upscaling was facilitated by the fact that N leaching was not different among sites or related to autotrophic epilithic biomass or assemblage composition. In conclusion, the capacity of epilithic biofilms to provide N to surrounding systems is an ecosystem service that underscores the necessity to conserve them and their habitats.     

Species poor but distinct: bird assemblages in white sand vegetation in Jaú National Park, Brazilian Amazon

There have been few studies of the fauna of the distinctive vegetation that grows on sandy soil in Amazonia. Leached and nutrient-poor sandy soil is associated with a vegetation type that varies in structure from open fields (campinas) to low canopy forests (campinaranas). During a bird inventory in sandy soil vegetation at Jaú National Park (JNP), I recorded 128 bird species, with 55 in campina and 94 in campinarana. Estimates suggested only 150 bird species should be expected to occur in these habitats, a reduced species diversity compared with other vegetation types in the Amazon region. This low species diversity is probably linked to the low productivity of this habitat and its relatively simple vegetation structure. Despite the relatively low diversity, at least 14 bird species (3% of the entire avifauna) appear to be restricted to white sand vegetation in JNP. In Amazonia as a whole, some 37 bird species are associated with vegetation in sandy soils. Biological inventories of other taxa are needed to understand the contribution of white sandy vegetation to the faunal distribution in Amazonia.     

Genetic Relationships among Tall Coconut Palm (Cocos nucifera L.) Accessions of the International Coconut Genebank for Latin America and the Caribbean (ICG-LAC), Evaluated Using Microsatellite Markers (SSRs)

The diversity and genetic relationships among two accessions of tall coconut palms collected in Brazil and seven accessions introduced from different geographic regions of the world were analyzed using 25 microsatellite primers, 19 of which were polymorphic and detected between 4 and 10 alleles per locus, with an average of 6.57. The observed and expected heterozygosity ranged from 0.25 and 0.40 in the Rennell Islands Tall (RIT) accession to 0.54 and 0.62 in the Polynesian Tall (PYT) accession. The analysis of genetic structure resulted in the formation of five distinct groups. The first group was formed by the accessions Brazilian Tall—Praia do Forte (BRTPF), Brazilian Tall—Merepe (BRTMe) and West African Tall (WAT); the second group consisted of Malaysian Tall (MLT); the third group of RIT; the fourth group of Vanuatu Tall (VTT); and the fifth group of Rotuman Tall (RTMT), Tonga Tall (TONT) and PYT. The dendrogram based on the nearest-neighbor method detected the formation of two main groups and five subgroups, indicating that the genetic relationships of the accessions are based on their geographic regions of origin. The analyses revealed genetic relationships between the accessions collected in Brazil and the accession from Africa, and among palms from South East Asia and the South Pacific, confirming the common origin of these accessions. The information obtained in this study can guide decisions on germplasm conservation activities and the efficient selection of genetically divergent parents for use in coconut breeding programs in Brazil, which are attempting to select for disease resistance, mainly to lethal yellowing, among other characteristics.     

Shoot δ15N and δ13C values of non-host Brassica rapa change when exposed to ±Glomus etunicatum inoculum and three levels of phosphorus and nitrogen

Glasshouse experiments were conducted to study the response of non-host Brassica rapa and host Sorghum bicolor to inoculation with the arbuscular mycorrhizal fungus (AMF) Glomus etunicatum when given different levels of N (0.9 mmol kg^-1 sand, 2.7 mmol kg^-1 sand, 8.1 mmol kg^-1 sand) and P (3.6 µmol kg^-1 sand, 10.7 µmol kg^-1 sand, 32.0 µmol kg^-1 sand) fertiliser. On both plant species, the presence of G. etunicatum inoculum (+AMF) was associated with significant changes of shoot '¹⁵N values, with +AMF plants having larger average '¹⁵N values than uninoculated plants (-AMF). These values are the largest average differences in shoot '¹⁵N yet recorded for AMF and nutrient effects. B. rapa shoot '¹⁵N average differences ranged from 1.67‰ to 2.70‰, while for S. bicolor they range between 2.07‰ and 4.40‰. For shoot '¹³C only the non-host B. rapa responded to -AMF and added N. Although the harvested dry weight biomass (-35.2% B. rapa; +39.8% S. bicolor) of both plant species responded to AMF inoculation, no direct relationship was observed between isotopic discrimination and growth inhibition for the non-host B. rapa. In this paper we discuss some implications regarding AMF inocula on the basis of our findings and current literature.     

A new approach to an unbiased estimate of the hepatic stellate cell index in the rat liver: an example in healthy conditions.

Evaluation of activation and proliferation of hepatic stellate cells (HSCs) must be grounded on solid quantitative data under normal conditions. The HSC index (HSCI), number of HSCs per 1000 hepatocytes (HEP), is often used in hepatology but has been never determined using stereology. Systematically sampled sections were immunostained against glial fibrillary acidic protein and carcinoembryonic antigen, allowing unequivocal distinction of HSC and mononuclear/binuclear HEP. With the optical disector the HSCI was estimated as 109 (coefficient of error = 0.04). This work provides a sound technical basis for experiments in which the estimation of HSCI and/or simultaneous quantification of HSC and HEP are relevant.     

SlBBX28 positively regulates plant growth and flower number in an auxin-mediated manner in tomato

Plant Molecular Biology - SlBBX28 is a positive regulator of auxin metabolism and signaling, affecting plant growth and flower number in tomato B-box domain-containing proteins (BBXs) comprise a...