甘蔗与蔗茅杂交双亲染色体在F_1及F_2子代中的传递

甘蔗与蔗茅杂交的后代材料抗旱、耐寒,在甘蔗抗逆育种中具有较好的应用前景,为将其有效应用于甘蔗新品种的选育及品种改良,特对甘蔗与蔗茅杂交各世代的染色体传递方式进行研究。采用去壁低渗法对F1、F2杂种及其亲本材料的根尖体细胞染色体进行研究。结果表明:各后代材料的体细胞染色体数目均不恒定,F1材料的染色体变幅为10~11条,F2材料的变幅为6~14条;双亲染色体在F1代材料中的传递方式为"2n+n",而在F2中既以"n+n"又以"2n+n"的方式进行传递。本研究结果可为诸类材料在甘蔗育种中的进一步利用提供细胞学依据。     

Hydrosedimentology of nested subtropical watersheds with native and eucalyptus forests

Purpose

Information on the effects of eucalyptus forests on hydrosedimentological processes is scarce, particularly at the catchment scale. Monitoring and mathematical modeling are efficient scientific tools used to address the lack of information for natural resource management and the representation and prediction of those processes. This study evaluates the effects of eucalyptus cultivation on hydrosedimentological processes in watersheds and to use the Limburg soil erosion model (LISEM) to represent and predict hydrological processes.

Material and methods

The study was conducted in two forested watersheds: the main watershed (94.46 ha) and a nested sub-watershed (38.86 ha), both cultivated with eucalyptus and residual riparian native forest, located in southern Brazil. Hydrosedimentalogical monitoring was conducted from 16th February 2011 to 31st December 2012, and LISEM model calibrations were performed on the bases of six storms events.

Results and discussion

The sediment yield for 2011 was 41.6 Mg km^?2 and 38.5 Mg km^?2 for the watershed and sub-watershed, respectively. An extreme event in 2012 provided greater sediment yield for the sub-watershed (99.8 Mg km^?2) than that for the watershed (51.7 Mg km^?2). Rainfall events with a greater maximum intensity generated rapid discharge and suspended sediment concentration responses in the sub-watershed due to the smaller drainage area and steeper landscape. In the main watershed, the accumulation of flood waves occurred for most events, with less steep hydrographs, and a later occurrence of the discharge peak after that of the sub-watershed. The LISEM adequately reproduced the peak discharge and runoff for the calibrated events; however, the peak time and the shape of the hydrograph were not adequately represented.

Conclusions

The hydrosedimentological patterns of the watershed and sub-watershed, both cultivated with eucalyptus, was characterized by sedimentographs preceding hydrographs during rainfall–runoff events where scale effects occur, with maximum discharge and specific sediment yield greater in the watershed than that in the sub-watershed. Empirical models based on hydrologic variables may be used for estimating the suspended sediment concentration and sediment yield. Therefore, LISEM may be used for the prediction of hydrological variables in these forested watersheds.     

Screening Mangrove Endophytic Fungi for Antimalarial Natural Products

We conducted a screening campaign to investigate fungi as a source for new antimalarial compounds. A subset of our fungal collection comprising Chinese mangrove endophytes provided over 5000 lipophilic extracts. We developed an accelerated discovery program based on small-scale cultivation for crude extract screening and a high-throughput malaria assay. Criteria for hits were developed and high priority hits were subjected to scale-up cultivation. Extracts from large scale cultivation were fractionated and these fractions subjected to both in vitro malaria and cytotoxicity screening. Criteria for advancing fractions to purification were developed, including the introduction of a selectivity index and by dereplication of known metabolites. From the Chinese mangrove endophytes, four new compounds (14–16, 18) were isolated including a new dimeric tetrahydroxanthone, dicerandrol D (14), which was found to display the most favorable bioactivity profile.     

Histopathology of postbloom fruit drop caused by Colletotrichum acutatum in citrus flowers

Postbloom fruit drop (PFD) is caused by both Colletotrichum acutatum and C. gloeosporioides and is a potentially serious disease in citrus that occurs when flowering coincides with rainfall. The fungus incites necrotic lesions in petals and stigmas leading to premature fruit drop and reduced yield. The mechanisms of infection and survival of the causal agents remain to be fully elucidated. In the present study, we investigated the histopathology of PFD caused by C. acutatum in the petals and stigmas of sweet oranges using electron and light microscopy. In the petals, pathogen penetration occurred intra and intercellularly and also through the stomata, with intercellular penetration occurring most frequently. The distinct tissues of the petals were colonised, including the vascular system, particularly the xylem. Acervuli were observed on both sides of the petals. Although the fungus did not penetrate through the epidermal cells of the stigma, C. acutatum caused necrosis and an increase of phenolics in this tissue. A protective layer rich in lipophilic and phenolic compounds was formed under the necrotic area and crystals of oxalate were associated with the sites where the pathogen was present.     

Infection of citrus pollen grains by Colletotrichum acutatum

Postbloom fruit drop (PFD), an important disease caused by Colletotrichum spp., affects citrus yields in Brazil. PFD is characterised by the presence of necrotic lesions on the petals and stigmas of citrus flowers and by the subsequent abscission of young fruit. PFD epidemics have high disease progress rates, which is unusual for a pathogen that produces acervuli and is dispersed by rain. It is possible that other dispersal agents, such as insects and pollen, are involved in the spread of this disease. The objective of this work was to test whether citrus pollen grains can be colonised by Colletotrichum acutatum. Studies using light and electron microscopy showed that the pollen of Citrus sinensis can be infected by C. acutatum. This pathogen can penetrate and colonise citrus pollen grains 24 h after inoculation with the pathogen. The germ tube of conidia either penetrates the pollen sporodermis directly or passes through pollen germ pores. A single hypha can colonise more than one pollen grain. On the surface of the stigma, conidium formation can be observed. This study shows that Citrus sinensis pollen may, in fact, play a role in the spread of C. acutatum in citrus orchards.     

Development and characterization of a monoclonal antibody against porcine CD205

The aim of this work was to develop mAbs against porcine CD205 and to conduct a comparative analysis of the CD205 protein expression on lymphoid tissues, monocyte-derived dendritic cells (DCs) and DCs isolated from the porcine skin. To conduct this study, we generated a monoclonal antibody, designated 1.F6F6, against the C-type lectin-like domain-5 of the porcine CD205 and showed that it recognizes a protein band of ～200 kDa by Western Blot analysis in mesenteric lymph nodes cells. Flow cytometric analysis showed that the mAb 1.F6F6 recognized 28.5%, 28.1% and 34.1% of cells from tonsil, inguinal and mesenteric lymph nodes, respectively, and 6% of cells from thymus. Analysis of monocyte-derived DCs showed that approximately 20% were positive and activation of the cells with LPS increased the positive population to 36%. Analysis of DCs isolated from the porcine skin showed that approximately 70% of the cell population expressed the CD205 receptor. The development of a monoclonal antibody capable of recognizing the CD205 receptor in swine opens up possibilities of applying new strategies for enhancing vaccine efficacy by using the anti-CD205 antibody for DC antigen-targeting to enhance priming of immune responses.     

New Insights on the Terpenome of the Red Seaweed Laurencia dendroidea (Florideophyceae,Rhodophyta)

The red seaweeds belonging to the genus Laurencia are well known as halogenated secondary metabolites producers, mainly terpenoids and acetogennins. Several of these chemicals exhibit important ecological roles and biotechnological applications. However, knowledge regarding the genes involved in the biosynthesis of these compounds is still very limited. We detected 20 different genes involved in the biosynthesis of terpenoid precursors, and 21 different genes coding for terpene synthases that are responsible for the chemical modifications of the terpenoid precursors, resulting in a high diversity of carbon chemical skeletons. In addition, we demonstrate through molecular and cytochemical approaches the occurrence of the mevalonate pathway involved in the biosynthesis of terpenes in L. dendroidea. This is the first report on terpene synthase genes in seaweeds, enabling further studies on possible heterologous biosynthesis of terpenes from L. dendroidea exhibiting ecological or biotechnological interest.     

Relative importance of inoculum sources of Guignardia citricarpa on the citrus black spot epidemic in Brazil

Guignardia citricarpa, the causal agent of citrus black spot (CBS), forms ascospores and conidia in citrus leaf litter and only conidia on fruit and twigs. The objective of this work was to determine the relative importance of inoculum sources of ascospores and conidia in the progress of CBS under natural conditions in Brazil. A first experiment was conducted in an orchard subdivided into two areas. In one area, fallen leaves were removed and in the other area fallen leaves were maintained. In each area, two treatments were established: 1) CBS symptomatic mature fruit remained on the trees after the new fruit set, and 2) CBS symptomatic mature fruit were harvested before the new fruit set. A second experiment was carried out in a CBS-free experimental orchard where detached symptomatic fruit and leaf litter on the orchard floor and detached symptomatic fruit and dead twigs on the tree canopy were distributed to investigate the spread of disease. In the first experiment disease incidence was similar for all treatments in all years. However, in 2003, in the area without leaf litter (absence of the ascospores source), disease intensity and the rate of progress of disease incidence were higher when there was overlap of mature and young fruit. In the second experiment, only detached symptomatic fruit and dead twigs on the tree canopy were able to spread CBS in two years of the experiment. The distance of disease spread was less than 80 cm from these inoculum sources. The removal of fallen leaves was not sufficient to completely suppress the disease because of the presence of conidia in fruit and dead twigs. Therefore the reduction of conidia sources should be considered in CBS management in Brazil.