苹果锈病的发生及防治

苹果锈病(Gymnosporangium yamadai? Miyabe)又名赤星病、苹桧锈病、水锈病、羊胡子,是一种真菌病害,主要为害苹果、海棠、山定子等,尤其是桧柏种植区附近的苹果树易发生锈病,发病后削弱树势,造成叶片枯黄脱落、果实畸形早落,严重影响树体产量和果实品质。     

梨锈病的症状及综合防治技术

<正>梨锈病又名梨赤星病、羊胡子病,是梨树的主要病害之一,在我国南北果园均有发生。除危害梨树外,还可危害山楂、贴梗海棠和堂梨等。但不危害苹果,病原菌为转主寄生的锈菌,其转主寄主为桧柏、圆柏、龙柏、柱柏、翠柏、球柏、金羽柏、欧洲刺柏、欧洲柏、高塔柏等,其中以桧柏为主要寄主。因此,凡梨园周围种有桧柏或附近的学校,机关、工矿企业等种有桧柏的附近梨园,梨园的锈病发病就会特别严重。     

垂丝海棠锈病的发生与综合防治技术

<正>垂丝海棠为海棠四品之一,是一种重要园林观赏树木和盆景材料。在园林绿化中,常与桧柏、侧柏、龙柏、铺地柏等混植,造成锈病发生逐年加重。据笔者近2年调查,在江苏、上海等地病株率85%以上,病叶率在40%～70%,致使叶片枯黄早落。该病同时还会危害桧柏、侧柏、龙柏、铺地柏等观赏树木,引起针叶及小枝枯死,影响园林景观。     

梨不同品种田间锈病抗性调查

梨不同品种田间锈病抗性调查李树玲，黄礼森（中国农业科学院果树研究所，辽宁兴城１２５１００）梨锈病即赤星病（ＧｙｍｎｏｓｐｏｒａｎｇｉｕｍｈａｒａｅａｎｕｍＳｙｄ．）是梨产区普遍发生的一种病害。随着城乡绿化事业的发展，梨锈病中间寄主桧柏逐年增多，为此病...     

梨锈病在不同品种上的发病情况调查

梨锈病又名赤星病,是梨树上的重要病害之一。近年来,随着城乡绿化的进一步发展,在梨园附近有桧柏、龙柏等转主寄主的地方,该病发生严重。为了明确不同品种间     

重茬土对不同品种海棠生长的影响

以5个不同海棠品种为试材,选取平邑甜茶为砧木,分别对海棠生长量及叶片营养进行测定,研究了重茬土对相同砧木不同海棠品种生长的影响。结果表明:同一块重茬地中,相同砧木不同海棠品种生长量及叶片矿质营养含量存在一定的差异;E5和E24品种生长存在优势,可作为抗重茬品种进一步培养。     

苹果锈病的发生与防治

苹果锈病又叫赤星病,近两年来,苹果锈病在我市西山七县都有不同程度的发生,桧柏栽植越多的乡镇发生面积越大,桧柏周边的果园病情越严重。发生锈病的叶片全部萎蔫变黄变褐,病斑密布,叶片背部长出羊胡子状的锈子器,远看满园果叶像是被火烤水烫一般,幼果     

7个海棠品种对梨火疫病菌的抗病性评价

2022年，以新疆北疆地区种植的7个常见的海棠品种为试材，对离体的叶片、枝条和幼果均采用针刺接种的方法，鉴定其对梨火疫病的抗病性。结果表明：7个海棠品种对梨火疫病抗性不同，离体叶片接种鉴定结果表明王族海棠为高抗品种，贴梗海棠、绚丽海棠、高酸海棠为抗病品种，光辉海棠、黄太平、锦绣海棠为感病品种；离体枝条和幼果接种鉴定结果表明王族海棠为高抗品种，贴梗海棠、绚丽海棠为抗病品种，高酸海棠、锦绣海棠为感病品种，光辉海棠、黄太平为高感品种。综合认为，在北疆地区，王族海棠高抗梨火疫病，贴梗海棠和绚丽海棠抗梨火疫病，均可作为新疆城市街道种植景观海棠备选品种。     

梨、苹果锈病转主寄主的研究

<正> 经在陕西地区研究发现,苹果锈病和梨锈病两种锈菌的转主寄主是不同类型的桧柏:梨锈菌的转主寄主是两型叶桧柏,其树冠较稀疏,分枝角度较大,具针叶和鳞叶,锈菌在其上形成纺锤形瘿瘤,梨锈菌也可寄生于龙柏;苹果锈菌的转主寄主是针叶型桧柏,其树冠较紧凑,分枝角度小,只具针叶,锈菌在其上形成球形或半球形的瘿瘤。另外,     

西府海棠常见病虫害及综合防治

西府海棠属蔷薇科苹果属落叶小乔木,适应性强,抗干旱、耐盐碱,萌芽力强,生长迅速,耐修剪。近年来,在园林绿化中由于经常与桧柏、河南桧等植物混合栽植,病虫害发生越来越严重,我们通过对蓟县公共绿地、园林苗圃进行调查研究,基本掌握了西府海棠常见病虫害的发生规律及防治方法。     

A mathematical comment on the formulae for the aggregation index and the shape index

Ina recent paper [Landscape Ecol. 15: 591–601 (2000)] He et al. describedanaggregation index AI _i to measure pixelaggregation within a single class i. We show that thecommonly used shape index SI _i is related to theproposed aggregation metric as SI _i =(A _i) +AI _i(1 –(A _i)), with(A _i) dependent on class areaA _i only. Moreover, it is shown that thenormalized shape index, SI _i ^*,equals (1 – AI _i). We conclude thatAI _i does not provide any information notprovided by SI _i, orSI _i ^*.This revised version was published online in May 2005 with corrections to the Cover Date.     

Quantifying the nitrogen retention capacity of natural wetlands in the large-scale drainage basin of the Baltic Sea

We estimate the nitrogen retention capacity of natural wetlands in the 1.7 million km² Baltic Sea drainage basin, using a wetland GIS data base. There are approximately 138,000 km² of wetlands (bogs and fens) in the Baltic Sea drainage basin, corresponding to 8% of the area. The input of nitrogen to natural wetlands from atmospheric deposition was estimated to 55,000–161,000 ton y¹. A map of the deposition of both wet and dry nitrogen is presented. The input from the human population was estimated to 255,000 ton y¹ in terms of excretory release in processed sewage water. There may also be leakage from forests and agricultural land into the wetlands. Due to lack of data on hydrology and topography, such potential nitrogen sources are not accounted for here. The capacity of the wetlands to retain the atmospheric deposition of nitrogen was estimated to 34,000–99,000 ton y¹. The potential retention by wetlands was estimated to 57,000–145,000 ton y¹ when the nitrogen input from the human population was added. If drained wetlands were to be restored and their area added to the present wetland area, the nitrogen retention capacity was estimated to increase to 196,000–261,000 ton y¹. Our results indicate that existing natural wetlands in the Baltic Sea drainage basin annually can retain an amount of nitrogen which corresponds to about 5–13% of annual total (natural and anthropogenic) nitrogen emissions entering the Baltic Sea. The ecosystem retention service performed by wetlands accounts for a substantial nitrogen removal, thereby reducing the eutrophication of the Baltic Sea.     

Effects of cerium on the antioxidant defence system in the petals and the contents of pigments in the calyces of Rosa chinensis Jacq. cut flower

To study the role of cerium (Ce) in regulating the vase life of Rosa chinensis Jacq. cut flowers, the effects of cerium nitrate (Ce(NO₃)₃) on the activities of antioxidant enzymes, the contents of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) in the petals, and the contents of chlorophyll a, chlorophyll b and carotenoids in the calyces were investigated. The results showed that Ce(NO₃)₃ evidently enhanced the activities of peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), glutathione S-transferase (GST) and glutathione peroxidase (GPX), and evidently decreased the contents of MDA and H₂O₂ in the petals, compared with the control. Moreover, Ce(NO₃)₃ evidently increased the contents of chlorophyll a, chlorophyll b and carotenoids in the calyces. The results also showed that Ce(NO₃)₃ evidently increased the numbers of open flowers and decreased the numbers of wilted flowers. Our results suggest that Ce(NO₃)₃ extended the vase life of R. chinensis Jacq. cut flower by improving the antioxidant defence system in the petals and the contents of pigments in the calyces.     

Seeing the oakscape beyond the forest: a landscape approach to the oak regeneration in Europe

Context

Intensification and specialisation of agriculture and forest use has led to profound structural and compositional changes in European landscapes. In particular, sharp, narrow edges adjacent to relatively homogenous vegetation types progressively replace transitional habitats, crucial for a plethora of species and ecological processes. Quercus robur and Q. petraea regeneration niches make them best adapted to such transitional habitats. However, contemporary oaks’ importance, including their regeneration, is usually considered within limits of forest habitats.

Objective

Defining habitats, landscape patterns and processes fostering oak regeneration and ‘oakscape’ development.

Methods

We assessed the state-of-the art of the topical literature with respect to various aspects of oak regeneration based on a refined list of 234 titles from the Web of Science database.

Results

The review confirmed that the vast majority of studies focus on forest habitats, disregarding the fact that substantial part of acorns are being carried away and seeded by birds in non-forest habitats.

Conclusions

The common acceptance of the simplistic landscape mosaic model, based on segregated homogenous vegetation categories and clear-cut lines separating patches, impedes proper assessment of landscape changes, referring to ‘untypical’, transitional habitats—the true oaks’ domain. Hence, restoring and sustaining European ‘oakscape’ should result from the overall landscape management, based on a better adapted gradient approach to landscape studies. Applying such an approach, we identified a set of habitats fostering successful oak regeneration and recruitment without direct human support, contributing to the contemporary ‘oakscape’, represented mostly by non-forest, either natural or anthropogenic habitats.

     

Studies on the possible role of micropropagation in the dissemination of the strawberry crown rot pathogen Phytophthora cactorum

Summary

Attempts to develop a method for establishing latent infection by the crown rot pathogen (P. cactorum) in strawberry stolon tips or unrooted plantlets were largely unsuccessful. One month after dipping stolon tips in suspensions of zoospores (from 10 to 10³ ml^?1) 6% had died and 6% had become severely necrotic; only 2% of stolons with no obvious necrosis yielded P. cactorum in isolation on a selective medium. When young, pre-rooted plantlets were sprayed with more concentrated zoospore suspensions (from 10³ to 10⁵ ml^?1) and grown on for only one week, 9% died, 51% became necrotic and 40% remained apparently healthy; 22% of the “healthy” plantlets yielded P. cactorum. The frequency of isolation from different parts of the plantlets indicated that most infections originated in the base of the crown, probably via root initials. When 298 stolon tips and 357 meristems were excised from symptomless plantlets one week after inoculation with a suspension of 10⁴ zoospores per ml, P. cactorum grew conspicuously into the culture medium and killed the plant tissue in 6% of stolon tip cultures and in 0.8% of meristem cultures. Of 380 micropropagation cultures successfully established from explants after inoculation not one yielded the pathogen on destructive sampling although other microorganisms were detected. It is concluded that the crown rot fungus does not become cryptically established in micropropagation cultures of strawberry and that, conversely, the technique of micropropagation is a reliable way of ensuring freedom from this pathogen in plant material.     

Metabolic process of the C-sugars on the translocation pathways of cucumber plants

Studies on the metabolic process of photoassimilates and enhancement of sugar accumulation into fruit are important in fruit crop production. The metabolic process of the ¹⁴C-photoassimilates in cucumber plants was analyzed with respect to the vascular system. At 4 h after the start of ¹⁴CO₂ feeding, the ¹⁴C-photoassimilates synthesized in a selected leaf on the main shoot were translocated to the vascular bundles of the internode just below the ¹⁴CO₂-fed leaf. The radioactivity of ¹⁴C-stachyose was as high as that of ¹⁴C-sucrose in the vascular bundles of petiole and internode just below the ¹⁴CO₂-fed leaf as well as in the midrib, while the radioactivity of ¹⁴C-stachyose was lower than that of ¹⁴C-sucrose in the mesophyll. The ¹⁴C-photoassimilates appeared to have been translocated without any metabolic change in the translocation pathways between the petiole and internode just below the ¹⁴CO₂-fed leaf, because the ratio of ¹⁴C-stachyose radioactivity in the two parts was similar. At 8 h after the start of ¹⁴CO₂ feeding, the ¹⁴C-photoassimilates were translocated to the fruit. In the vascular bundles of the peduncle, the ratios of the radioactivity of ¹⁴C-stachyose and ¹⁴C-raffinose were lower, and the ratio of the radioactivity of ¹⁴C-sucrose was higher, than that at the petiole and internode just below the ¹⁴CO₂-fed leaf at 8 h after the start of ¹⁴CO₂ feeding. Therefore, it seemed that ¹⁴C-stachyose and ¹⁴C-raffinose were hydrolyzed to ¹⁴C-sucrose in the peduncle.     

Phylogeny of the genus Phalaenopsis (Orchidaceae) with emphasis on the subgenus Phalaenopsis based on the sequences of the internal transcribed spacers 1 and 2 of rDNA

Summary

Phylogenies of 17 species of the genus Phalaenopsis and two related species were derived based on sequence analysis of the internal transcribed spacer 1 and 2 (ITS1 + ITS2) of ribosomal DNA. A genetic distance matrix was determined based on sequence length and base composition. Two phylogenetic trees were constructed following Maximum parsimony (MP) and the Neighbor-joining (NJ) methods. Seventeen Phalaenopsis species were shown to be a monophyletic group as supported by molecular data analysis from ITS1 and ITS2 sequences in this study. This result agreed that the genera Doritis and Kingidium could be treated as the genus Phalaenopsis. In addition, members of subgenus Phalaenopsis are not a monophyletic group. Within the subgenus Phalaenopsis, members of section Phalaenopsis are a monophyletic group. Both section Stauroglottis and Deliciosae are not monophyletic groups. Furthermore, members of the section Deliciosae and Esmeralda of subgenus Phalaenopsis are closer to subgenera Parishianae, Proboscidioides and Aphyllae and separated from the other Phalaenopsis species. In conclusion, this study supports the systematics of the genus Phalaenopsis at the generic level but not at the subgeneric level.     

Biophysical influences on the spatial distribution of fire in the desert grassland region of the southwestern USA

Context

Fire is an important driver of ecological processes in semiarid systems and serves a vital role in shrub-grass interactions. In desert grasslands of the southwestern US, the loss of fire has been implicated as a primary cause of shrub encroachment. Where fires can currently be re-introduced given past state changes and recent restoration actions, however, is unknown and controversial.

Objectives

Our objective was to evaluate the interactive effects of climate, urban development, and topo-edaphic properties on fire distribution in the desert grassland region of the southwestern United States.

Methods

We characterized the spatial distribution of fire in the Chihuahuan Desert and Madrean Archipelago ecoregions and investigated the influence of soil properties and ecological site groups compared to other commonly used biophysical variables using multi-model inference.

Results

Soil-landscape properties significantly influenced the spatial distribution of fire ignitions. Fine-textured bottomland ecological site classes experienced more fires than expected in contrast to upland sites with coarse soil textures and high fragment content that experienced fewer fire ignitions than expected. Influences of mean annual precipitation, distance to road/rail, soil available water holding capacity (AWHC) and topographic variables varied between ecoregions and political jurisdictions and by fire season. AWHC explained more variability of fire ignitions in the Madrean Archipelago compared to the Chihuahuan Desert.

Conclusions

Understanding the spatiotemporal distribution of recent fires in desert grasslands is needed to manage fire and predict responses to climate change. The use of landscape units such as ecological sites presents an opportunity to improve predictions at management scales.

     

High-contrast three-dimensional imaging of the Arabidopsis leaf enables the analysis of cell dimensions in the epidermis and mesophyll

Background  

Despite the wide spread application of confocal and multiphoton laser scanning microscopy in plant biology, leaf phenotype assessment still relies on two-dimensional imaging with a limited appreciation of the cells' structural context and an inherent inaccuracy of cell measurements. Here, a successful procedure for the three-dimensional imaging and analysis of plant leaves is presented.     

Development of the female gametophyte in the sterile ecotype of the bolting Allium sativum L.

Manifestations of female sterility were investigated in a sterile bolting ecotype of Allium sativum (garlic). Morphological studies revealed interference during the formation of integuments around the nucellus and the lack of a micropylar channel and anatomical studies revealed disorders in female gametophyte formation. As the consequence of developmental abnormalities ovule abortion was observed. Finally, significant differences were revealed between 2D protein profiles of sterile ovules of A. sativum and fertile ovules of Allium tuberosum. Further possibilities of application of modern proteomic tools to identify proteins responsible for developmental changes in sterile ovules of A. sativum are discussed.