Fine structure of phloematic trypanosomatid–coconut tree interaction

Phytomonas wilt or Hartrot is a fatal disease of palm (Arecaceae) species including Cocos nucifera (coconut) and is caused by a phloematic trypanosomatid, a promastigote parasite that inhabits phloem sieve elements of disease palms. In the present work, we described the morphology of the interaction between a phloematic trypanosomatid (Phytomonas staheli) and C. nucifera. Two varieties and one ecotype of the adult coconut palm from northeast and southeast Brazil were analyzed, totaling 34,000 plants. Coconut palm losses due to Hartrot varied according to the variety or ecotype and geographic area. Occurrence of Hartrot was insignificant in Rio de Janeiro state (southeast), but in Bahia state (northeast) losses were substantial when appropriate cultural practices were not applied. Symptomatic and healthy palm tissues were analyzed by light and electron microscopy. Laboratory diagnoses revealed the twisted promastigote form of phloematic trypanosomatids in the extracts of shoot apex, leaves, stems and inflorescence in diseased plants, but not in the healthy ones. No parasites were found in the roots. Although the general anatomy of healthy and diseased palms was similar, callose deposition in the sieve plates was revealed by histochemistry and immunocytochemistry in the diseased tissue. Plugging by the P-protein and plastid alterations was also observed. Our observations strongly suggest that parasite traffic between sieve elements took place, although their cell bodies were larger than the sieve pores. Phloematic trypanosomatid proliferation in the sieve tube elements might interrupt the transport of phloem or/and consume plant nutrients. In addition, an association between the percentage of sieve elements colonized by pathogen in palm tissues and disease severity was established.     

Identification and partial characterization of a <Emphasis Type="Italic">Carica papaya</Emphasis>-infecting isolate of <Emphasis Type="Italic">Alfalfa mosaic virus</Emphasis> in Brazil

A Carica papaya plant with severe yellow leaf mosaic, leaf distortion, and systemic necrosis was found in the municipality of Piracicaba, state of São Paulo, Brazil. Transmission electron microscopy (TEM) analysis revealed the presence of potyvirus-like particles and bacilliform particles similar to those of the Alfamovirus genus. The potyvirus was identified as Papaya ringspot virus-type P (PRSV-P). Biological, serological, and molecular studies confirmed the bacilliform virus as an isolate of Alfalfa mosaic virus (AMV). Partial nucleotide and amino acid sequences of the coat protein gene of this AMV isolate shared 97–98% identity with the AMV isolates in the GenBank database. This report is the first of the natural infection of papaya plants by AMV.     

Characterization of Open-Pollinated Maize Varieties from Rio Grande do Sul State

Journal of Crop Science and Biotechnology - The morphological characterization allows one to estimate and evaluate the genetic distance among different varieties, identifying heterotrophic groups...     

Patterns of oocyte development in natural habitat and captive <Emphasis Type="Italic">Salminus hilarii</Emphasis> Valenciennes, 1850 (Teleostei: Characidae)

Fecundity and oocyte development in Salminus hilarii female brood stock were analyzed with the aim of investigating the impact of migration impediment on oogenesis. Histological analyses of the ovaries were performed in adult females caught in two different environments—the Tietê River (natural) and captivity—and the gonadossomatic index, oocyte diameter and fecundity determined. Five germ cell development stages (oogonium, perinucleolar, cortical alveoli, vitellogenic, ripe) and two other structures (postovulatory follicles and atretic oocytes) were observed in females caught in the river. Captive animals lacked the ripe oocytes and postovulatory follicles and had a relatively higher number of atretic oocytes. Females in captivity are known to produce larger oocytes, and they release fewer eggs in each spawn (absolute fecundity) when compared with animals that are able to migrate. Our results suggest that the Tietê River is undergoing alterations which are being reflected in the reproductive performance of S. hilarii, mainly due to the presence of atretic oocytes in females caught in the river. The lack of postovulatory follicles and ripe oocytes in captive animals reveals that migratory impediment negatively impacts final oocyte maturation. However, the stage of maturation reached is adequate for ovulation induction with hormone manipulation.     

Search for molecular markers linked to Liriomyza trifolii resistance in tomato

Resistance to many arthropods, including Liriomyza species, is known to be present in accessions of Lycopersicon hirsutum (f. typicum or f. glabratum). From the cross L. esculentum cv. Moneymaker and L. hirsutum f. glabratum G1561 100 F₂ plants were screened in a no-choice test for resistance to Liriomyza trifolii. The Bulked Segregant Analysis approach was used to find Random Amplified Polymorphic DNA markers linked to resistance. Two markers were located on chromosome 2. Restriction Fragment Length Polymorphisms constructed a more detailed genetic linkage map for part of chromosome 2. Kruskal-Wallis analysis showed that this chromosome harbored a Quantitative Trait Locus (QTL) for number of pupae, number of mines and damage. At least one major QTL is essential for resistance and this QTL is located on chromosome 2 nearby the location of the tomato probe TG451. This revised version was published online in July 2006 with corrections to the Cover Date.     

Nutrients Accumulation,Biometric, Chlorophyll and Potassium Indexes and Production in Minituber Potato as Function of Potassium Doses in Organic and Hydroponic Conditions

ABSTRACT

Potato is one of the most economically important crops in Brazil. In this crop, potassium (K) is the most accumulated nutrient and has significant and positive effect on potato plant growth and tuber yield. Thus, the aim of this work was to determine the effects of K doses on nutrients accumulation, biometric, chlorophyll, and K indexes in potato plants grown. Two experiments were installed simultaneously in an unheated greenhouse with Agata cultivar. The experiment 1 was carried out in pot with commercial organic substrate with five K doses (0, 0.66, 1.32, 1.98, and 2.64 g dm^3?1). The experiment 2, nominated hydroponic system, with washed sand above a layer of expanded clay pebbles where the plants received daily nutrient solution application. The treatments were five K doses (0.0, 2.5, 5.0, 7.5 e 10.0 mmol L^?1). The biometrics data were collected 21 days after emergence and at harvest. Both experiments were set at a randomized block design with four replications. In both experiments, no visual symptoms of deficiency or excess were observed but only in plants at 0 mmol L^?1 of K. In both experiments, K doses interacted with some biometric and chlorophyll indexes measured in the fourth completely expanded leaf with portable SPAD and Dualex devices, commonly used as a guide to in-season fertilizer N management, leading to recommend their use only in plants properly nourished in K. K critical concentration in the fourth fully expanded leaf was 61.7 g kg^?1.     

Invasive tilapia juveniles are associated with degraded river habitats

• 1. Invasions are a main concern for conservationists. Identification of causes that raise or promote an invader's success is one of the first steps for preventing and/or fighting against invasions.
• 2. In the Brazilian River Paraiba do Sul, juveniles of invasive tilapia Oreochromis niloticus were detected associated with degraded habitats (mainly pollution from various sources). The relative abundance of juveniles of the competitor native species pearl cichlid Geophagus brasiliensis, morphologically and ecologically very similar, was negatively associated with habitat degradation.
• 3. A species‐specific molecular marker was employed to permit unambiguous identification of these small juveniles (2–3 cm long), which represent the most vulnerable life stage of both species.
• 4. It is suggested that adaptation to degraded habitats is one of the characteristics of invasive species, and consequently habitat conservation and restoration may help to prevent fish invasions.

Copyright © 2008 John Wiley & Sons, Ltd.     

Decomposition rates of forest residues and soil fertility after clear‐cutting of Eucalyptus grandis stands in response to site management and fertilizer application

Forest residues (i.e. harvest residues and litter) are important nutrient sources for trees because soils of poor fertility are used for eucalypt plantations in Brazil. Understanding the dynamics of decomposition for these residues and their effects on soil fertility are relevant for the management of forest plantations. The objectives with this study were to assess the effects of forest residue management and fertilizer, both applied in the establishment of a Eucalyptus grandis Hill ex Maiden stand, on the decomposition rate (k), nutrient release and soil fertility after harvest of this stand. The treatments were applied to a plantation (R1). After 8 yr, R1 was clear‐cut and all of the treatments were reapplied to a new planting (R2). At the end of R1 (age of 8 yr), there was a reduction of 10% in the wood volume in the treatment with the forest residues removed and 36% reduction with no fertilizer application. At the end of 1 yr for plantation R2, these reductions were 30 and 57%, respectively. Residue decomposition under R2 was assessed by a new approach that involved collecting samples directly on the site without using litter bags. The k of forest residues was 3.6 for leaves, 1.2 for bark and 0.8 for branches. The application of small rates of N and P fertilizer did not influence the k of forest residues. In the first 300 days after clear‐cutting, approximately 50% of N, P, Ca, Mg and S and 80% of K in the forest residues were released. Even so, this did not result in significant changes in soil fertility levels. Only small reductions in soil N and P contents over time and changes in topsoil pH resulted from forest residue removal.     

Estructura del estroma conjuntivo del epidídimo del bovino cebú (Bos indicus)

Six adult Zébu cattle were used for a study of the histologic structure of the epididymus. Tissues were fixed in neutral formalin or in Bouin's solution. Tissues were prepared with parafin sectioning and stained with hematoxylin and eosin, Masson and Mallory's trichrome stain and with aldehyde fuchsin and Gomori's argentamine stains. The structure of the connective tissue stroma is described and compared with that of other mammals. The presence of smooth muscle within the stroma and within the tunica albuginea is described for the Zébu.