Infectious hypodermal and hematopoietic necrosis,a newly recognized virus disease of penaeid shrimp

Populations of the Pacific blue shrimp, Penaeus stylirostris, reared at the University of Arizona's experimental shrimp culture facility on Oahu in Hawaii from late 1980 through 1981, were severely affected by a highly acute and lethal disease of viral etiology. Also found to be susceptible to the disease were P. vannamei and P. monodon. The disease was named infectious hypodermal and hematopoietic necrosis (IHHN) disease to describe the principal lesions observed. The histopathology of acute and subacute IHHN disease in these species was dominated by the presence of conspicuous eosinophilic intranuclear-inclusion bodies of the Cowdry type A variety in ectodermally (especially the cuticular hypodermis) and mesodermally (especially the hematopoietic tissues) derived tissues that were undergoing necrosis. Electron microscopy of affected tissues demonstrated the presence of two or three types of virus-like particles with cubic morphology and diameters of 17 to 27 nm that suggest IHHN virus to be either a parvo- or picornavirus.     

Taura syndrome,a disease important to shrimp farms in the Americas

World Journal of Microbiology and Biotechnology -     

Cuticular lesions induced in grass shrimp exposed to hexavalent chromium

Adult grass shrimp were exposed to four concentrations (0.5, 1.0, 2.0 and 4.0 ppm) of hexavalent chromium for 28 days. At the end of the exposure period, over 50% of the surviving shrimp possessed cuticular lesions that had many of the gross characteristics of “shell disease.” These lesions were usually associated with articulations of the appendages and abdomen. Furthermore, it was found that at increasing levels of chromium exposure, there was a proportionate increase in the loss of limbs such that nearly 50% of the limbs were lost in grass shrimp exposed to the highest test concentration of chromium. Histological and ultrastructural examination of numerous lesions demonstrated a range of degenerative features within the subcuticular epithelium that included cytoplasmic vacuolization, mitochondrial swelling, chromatin emargination, and the presence of unusual nuclear inclusions that appear to indicate direct chromium toxicity. Additionally, a marked retardation in new epicuticle and exocuticle formation was observed in viable tissues associated with lesions in late premolt shrimp. It is proposed that chromium interferes with the normal functions of subcuticular epithelium, particularly cuticle formation, and subsequently causes structural weaknesses or perforations to develop in the cuticle of newly moted shrimp. Because of these chromium-induced exoskeletal deficiencies, a viaduct for pathogenic organisms (e.g., bacteria) and direct chromium influx is formed that perpetuates lesion development.     

Histopathology of aflatoxicosis in the marine shrimp Penaeus stylirostris and P. vannamei

The acute and subacute toxicity of aflatoxin B₁ to the marine shrimp Penaeus stylirostris and P. vannamei (Order: Decapoda, Class: Crustacea) was investigated. Experimental shrimp were exposed to a range of concentrations of the toxin directly by intramascular injection (from 2 to 160 μg aflatoxin B₁/g body weight), or by multiple per os dosing with the feed (from 53 to 300 μg aflatoxin B₁/g feed) for up to 25 days. The histopathogenesis of aflatoxicosis in the aflatoxin-exposed animals was followed and found to be time and dose dependent in the hepatopancreas, mandibular organ, and in the hematopoietic organs. Less significant and/or inconsistent lesions were also observed in other organs and tissues, but a time-dose dependency was not noted. The principal lesions of aflatoxicosis in penaeid shrimp occur in the hepatopancreas and the mandibular organ. In the former organ, subacute and acute aflatoxicosis is expressed as necrosis of the hepatopancreatic tubule epithelium that proceeds from the proximal (older) portion of the tubules, in the center of the organ, to the peripheral (younger) tubule tips. A marked intertubular hemocytic inflammation followed by encapsulation and fibrosis of affected tubules follows in subacute aflatoxicosis, but is not as developed as in acute aflatoxicosis. The mandibular organ in aflatoxicosis displays a necrosis of the peripheral epithelial cells of the cords within the gland that progresses proximally to the central vein. Only a slight hemocytic inflammation accompanies the degenerative changes in this latter organ.     

套袋苹果褐点病菌分类鉴定及致病性

2011和2012年山东栖霞、蓬莱、沂源等地套袋苹果果实出现了一种红褐色病斑。从病斑上分离获得两株枝顶孢属Acremonium真菌,其中一株产生头状排列的分生孢子,另一株产生链状排列的分生孢子。2个菌株都能从伤口侵染近成熟期的苹果果实,导致果肉细胞坏死,表面凹陷,形成红褐色坏死斑。2个菌株都不能侵染无伤果实。2个菌株的ITS、β-微管蛋白基因、核糖体大亚基（nucLSU）和小亚基（nucSSU）的DNA序列完全相同。依椐两个菌株的ITS和nucLSU的DNA序列和形态特征,将2个菌株鉴定为菌核生枝顶孢Acremonium sclerotigenum。A. sclerotigenum是一种机会真菌,条件适宜时可侵染套袋的苹果果实,导致褐色坏死病斑,称之为枝顶孢褐点病。     

黄精褐斑病的病原生物学特性

为明确发生在贵州省施秉县的黄精叶斑类病害的病原菌,通过形态学和分子生物学方法对病原菌进行了鉴定,并对其生物学特性进行了初步研究。形态特征及rDNA-ITS、β-tubulin和tef1多基因序列分析表明,该病原菌为棕榈拟盘多毛孢Pestalotiopsis trachicarpicola。生物学特性研究结果表明,该菌菌丝体适宜生长温度为15-30℃,最适温度为28℃;最适pH值为5;以葡萄糖为碳源、酵母浸膏为氮源比较适合菌丝体的生长;菌丝体生长的最佳培养基为PDA;光照对菌丝体生长无明显影响;菌丝体致死温度为45℃。     

对虾白斑综合征及其免疫防控

对虾是海水养殖的主导品种之一,在我国海洋农业中发挥重要作用。自20世纪90年代以来,白斑综合征频繁暴发,严重阻碍了对虾养殖业的健康发展。经过十几年的不懈努力,对虾白斑综合征暴发机制及其免疫防控研究发展迅速,取得了重要进展。简述了对虾白斑综合征和对虾抗病毒免疫的基本特征,总结了运用多种免疫学原理和技术途径在对虾中进行白斑综合征疫病防控所取得的主要成果,并概括了应用不同策略进行免疫防控的保护效果,以期为对虾养殖业的健康持续发展提供参考。     

白斑综合症病毒与对虾血淋巴细胞的体外结合实验

通过差速离心和蔗糖密度梯度离心,从感染了白斑综合症病毒(WSSV)的病虾头胸部分离了WSSV,利用地高辛对病毒蛋白进行了标记(DIG-WSSV),以体外培养的对虾血淋巴细胞为吸附基底,观察和分析了病毒与细胞间的结合现象及特性。以NBT/BCIP为酶反应显色底物观察到在细胞周围形成许多暗紫色颗粒,证实病毒与细胞间存在着稳定的结合。以OPD为酶反应显色底物分析了结合反应的特性:当DIG-WSSV维持恒定值时,随着血淋巴细胞数量的增加结合显色增强,细胞数量达到1.2104cells/孔,492nm处的吸光值达到饱和;当血淋巴细胞数量维持恒定值时,随着DIG-WSSV蛋白含量的增加显色增强,且在DIG-WSSV的蛋白浓度达到4g/孔时,492nm处的吸光值达到饱和;未标记WSSV可竞争抑制血淋巴细胞与DIG-WSSV间的结合作用。进一步的研究得出:4℃下,随着结合时间的延长显色增强,但继续延长结合时间显色反而减弱;缓冲液的渗透压对结合结果影响甚微,而酸性条件利于病毒与细胞间的结合。37℃孵育对病毒结合活性影响不大,55℃和70℃孵育可显著影响病毒的结合活性;短时间超声波处理病毒可增加病毒结合能力,长时间超声波处理可破坏病毒结合能力;有机溶剂处理同样可破坏病毒结合能力,其中尤以氯仿/甲醇的处理更为激烈;不同的去垢剂对病毒结合活性的影响结果不同:SDS和脱氧胆酸钠可以降低病毒的结合活性,而Triton X-100和NP-40可以提高病毒的结合活性。       

An antagonistic actinomycete for suppression of tobacco brown spot

We have identified a promising antagonistic micro-organism for suppressing brown spot disease. This isolate (strain 182-2) was found belonging to Streptomyces cacaoi. Strain 182-2 and its bacteria-free culture broth filtrate showed inhibitory effects both in vitro and in vivo, and is highly stable. Strain 182-2 has great potential to be developed as a commercial agent.     

Identification and fine-mapping of a bacterial brown spot disease resistance gene in maize

Bacterial brown spot (BBS) in maize (Zea mays L.) is caused by Pseudomonas syringae pv. syringae Van Holl (Pss). In China, this disease is not prevalent in maize at present. Here, we report the identification and fine mapping of the gene, referred to as Psy1, which confers resistance to BBS. An F₂ population, derived from the cross P25/F349, was used for linkage analysis and mapping of the resistance gene Psy1. Analysis of a BC₈F₂ population, derived from the same parents, confirmed that Psy1 was located on chromosome 10L and inherited as a single dominant gene. For fine mapping of Psy1, two introgression lines, X41 and X44, homozygous at the resistant gene locus, were introduced to hybridize with the susceptible parent P25 respectively, and developed a mixed BC₁ population. We found the closest markers to Psy1 are EST1 and FG29-3, which located on two adjacent BACs respectively, based on the B73 BAC sequence. Sequence analysis of these two BAC sequences (~300 kb) revealed the presence of a homologous sequence of receptor-like kinase. Also a co-segregation marker was developed based on this homologous sequence. These results will be useful for cloning of Psy1 and for transferring or pyramiding Psy1 through MAS in maize breeding programs.     

A comparative screening of hybrid,modern varieties and local rice cultivar for brown leaf spot disease susceptibility and yield performance

Five rice cultivars, one hybrid (WR96), three modern (BR16, BR26, and BRRI Dhan27) and one local (Pari) were screened for reaction to brown leaf spot disease caused by Cochliobolus miyabeanus and performance of yield-related characters. The severity of brown leaf spot varied with growth stages of rice plant as well as different cultivars tested under field condition. Low disease severity was observed at maximum tillering stage compared to moderate to high at dough stage, with hybrid cultivar WR96 showing highest disease, while local cultivar Pari had the lowest. Brown spot disease severity in different cultivars under induced epiphytic condition also followed the similar trend. The results also revealed that most of the yield-contributing characters examined showed wide variations among the cultivars. Modern cultivar BR16 produced the highest panicle length, number of grain per panicle and grain yield per hectare. At the same time as local cultivar Pari generated the lowest number of tiller per plant, panicle length, grain number per panicle and grain yield per hectare. Moreover, hybrid cultivar WR96 produced the highest percentage of spotted grain per panicle and seed yielding C. miyabeanus, and also the lower percentage of seed germination, while the reverse was observed in local cultivar Pari. These findings may allow producers and breeders to select rice cultivar, resistant or tolerant to brown leaf spot disease and to avoid significant reductions in grain yields.     

Observations on the pathogenesis of the imperfect fungus,Fusarium solani,in the California brown shrimp,Penaeus californiensis

The pathogenesis of Fusarium solani infections was studied using a highly susceptible species, Penaeus californiensis. In two experiments, F. solani infections were established in artificially wounded and infected juvenile and adults of P. californiensis, while similar control groups were wounded but not artificially infected. In the first experiment, the progress of F. solani infections in 15-g cultured juveniles of P. californiensis was followed by gross inspection and by light and electron microscopical study of the wound area. Developing F. solani infections were produced with a success rate of 100% within 14 days postinfection, and deaths due to disease of greater than 50% of the artificially infected group had occurred by 24 days postinfection. Infections were histologically characterized by (1) expansion of lesions into the tissue surrounding the point of entry, (2) destruction of invaded tissues by host granuloma formation and possibly by fungal enzymes and toxins, and (3) hemocyte encapsulation of hyphae with eventual melanization of the encapsulating hemocytes. In the second study, wild adult P. californiensis were artificially infected with F. solani, and changes in several of their hemolymph constituents [alkaline phosphatase, serum glutamic oxaloacetic transaminase (SGOT), glucose, total protein, hemocyte count, and hematopoietic tissue mitotic index] were determined as the disease developed. Significant differences occurred in these hemolymph parameters of shrimp with advanced F. solani infections compared to those of uninfected, unwounded control shrimp or those with early F. solani infections. Hemolymph from severely infected shrimp was hypoproteinemic, contained lower numbers of circulating hemocytes, and frequently failed to coagulate.     

Patterns of airborne conidia of Stemphylium vesicarium, the causal agent of brown spot disease of pears, in relation to weather conditions

Seven-day volumetric spore samplers were installed in pear orchards of northern Italy, in the years between 1993 and 2002, and operated continuously during the development of brown spot epidemics (mid-April–mid-August), caused by Stemphylium vesicarium. Aerial concentration of conidia was recorded at 2 h intervals to study their diurnal and seasonal patterns and the influence of weather conditions. The diurnal periodicity of aerial conidia showed a peak around midday and low counts in the dark. The increase in spore concentration was significantly correlated with the reduction of relative humidity and wetness in early morning, and the increase of wind in late morning and afternoon. Conidia of S. vesicarium became easily airborne to form a regular component of the air-spora in pear orchards, while ascospores were caught only sporadically. Differences between years concerned total spore counts and numbers of peaks (defined as days with more than 30 conidia/m³ air per day). Periods with highest spore counts occurred in late-May to early-June (in 2 years), mid to end of June (5 years), or after mid-July (3 years). There was a significant correlation between spore peaks and days with favourable weather conditions, defined as days with air temperature between 15 and 25°C and high humidity, particularly a wet period longer than 10 h. Occurrence of one or more consecutive days with favourable weather conditions determined an increase in the airborne concentration of conidia, which usually lasted some days and then decreased.     

响应面法优化北五味子褐斑病内生生防真菌淡紫拟青霉WG9发酵工艺及发酵产物稳定性研究

为提高北五味子内生生防真菌WG9发酵液对褐斑病病原菌的抑菌率,本研究采用单因素实验及响应面法对其发酵条件进行优化.首先采用单因素实验,以发酵时间(h)、发酵温度(℃)、摇床转速(r/min)及初始pH为考察指标,测定对病原菌的抑菌率及生防真菌WG9的菌丝体生物量,以获取单因素实验的最优值,然后使用Box-Behnken...     

Temporal distribution and abundance of shrimp postlarvae and juveniles in the mangroves of Muthupet,Tamilnadu, India

The temporal distribution patterns of the predominantly occurring postlarvae and juvenile shrimps in the mangrove and associated habitats of Muthupet, India were investigated for two years from February 1984 to January 1986. Among the eight commercially important species recorded, Penaeus indicus H. Milne Edwards, P. merguiensis De Man, P. monodon Fabricus and Metapenaeus dobsoni (Miers) were predominant. The postlarval recruitment size variedwith species: P. indicus and P. merguiensis recruited at the size of 9–11 mm total length (TL), P. monodon at 12–14 mm TL and M. dobsoni at 4–6 mm TL. The species P. indicus, P. merguiensis and M. dobsoni were observed continuously throughout the study period with maximum abundance occurring from July to September in 1984–85 and from August through October in 1985–86. P. monodon occurred seasonally from November to January in both years. Postlarvae and juvenile catches were low during low salinity and high salinity periods and a higher density was observed in the months of moderate water salinity. Large numbers of P. indicus, P. merguiensis and M. dobsoni clearly showed the preference to the detritus rich muddy substrate, whereas P. monodon did not show any preference and was equally abundant over different substrate types.     

Application of mitochondrial control region in population genetic studies of the shrimp Penaeus

This study reports a primer set for amplifying a partial fragment of about 610 bp in the fast mutating mitochondrial control region in shrimps of the genus Penaeus (Decapoda: Penaeidae). The utility of this amplified fragment for studying population differentiation and structuring, compared with more conservative mitochondrial genes (16S rRNA and COI), was explored in P. merguiensis populations over a vast geographical range based on sequence and RFLP analyses. The results indicate that the mitochondrial control region provides more informative sites and reveals more haplotypes, making it most useful for evaluating genetic variations within and between populations of Penaeus species.     

Biological control of mushroom brown blotch disease using antagonistic bacteria

Button mushroom brown blotch disease is one of the most important and devastating diseases in Iran which is caused by Pseudomonas tolaasii. To screen antagonistic bacteria against this pathogen, major mushroom cultivation centres in Iran were surveyed and samples were taken from compost, soil cover and button caps with or without visible symptoms. In total, 120 bacteria were isolated on the basis of their morphology and pathology on excised tissue blocks of the fresh Agaricus bisporus. Among all tested bacteria, thirty-six isolates produced variable inhibition zones and reduced the symptom incidence on tissue blocks of A. bisporus. The most effective antagonistic bacteria caused almost 100% inhibition of pathogenic bacterium. To confirm the identification of antagonistic bacteria, RNA polymerase beta-subunit gene (rpoB) of five antagonistic strains (A1, A2, A3, A4 and A6) were amplified using primer sets of long amplicon primers (LAPS) and LAP27. The polymerase chain reaction products of the strains A1, A3 and A6 were sequenced. Based on phenotypic, biochemical and molecular characteristics, the bacterial antagonists were identified as P. putida (A1), P. reactants (A2 and A6), P. fluorescens (A3 and A4) and Bacillus subtilis (A5), respectively. In all four criteria including weight of the diseased and healthy caps, per cent disease severity and per cent disease incidence, the treatment 2 (P. fluorescens A4) was the most effective from among T1, T3, T4 and T5 treatments. Overall results of this study suggest that bacterial antagonists may be potential biocontrol agents for biological promotion of the health and growth of button mushroom.     

Reproductive cycle of seabob shrimp Xiphopenaeus kroyeri (Crustacea,Penaeidea) from the northeast coast of Brazil

The reproductive cycle of Xiphopenaeus kroyeri north-eastern Brazil was described to contribute to the sustainable management of this stock in the region. Specimens were collected monthly from August 2011 to July 2012 using a local vessel of the artisanal fleet. A total of 1201 individuals were analyzed (673 females and 528 males) with a mean carapace length (CL) of 1.88 ± 0.16 cm and total length (TL) of 9.00 ± 1.22 cm. The lowest CL and TL of mature females were 1.33 and 6.5 cm, respectively, and all females above 2.44 cm (CL) and 11.5 cm (TL) were mature. Ovarian maturation was classified into four stages: I (immature), II (maturing), III (mature) and IV (spawned). Individuals of all maturational stages were present throughout the year. Considering the macro and microscopic analysis, it was suggested that this species in north-eastern Brazil has a continuous reproductive cycle, with two seasonal peaks, November/December and February (austral spring and summer). A positive correlation between the percentage of mature females and temperature was observed, and a higher percentage was reported in the warmer months of the year. This suggests that the reproductive peaks can be triggered by water temperature variation throughout the year.     

Hepatopancreas and ovary are sites of vitellogenin synthesis as determined from partial cDNA encoding of vitellogenin in the marine shrimp,Penaeus vannamei

Summary

The site of yolk protein synthesis in crustaceans has long been a subject of controversy. A portion of the vitellogenin gene structure was reported recently in a freshwater giant prawn (Macrobrachium rosenbergii) and black tiger shrimp (Penaeus monodori), in which the hepatopancreas was confirmed to be the extraovarian site of vitellogenin synthesis. The ovary is also frequently reported to be the site of yolk protein synthesis in penaeid shrimp. The same PCR product was obtained using cDNA from the hepatopancreas or the ovary as a template. The deduced amino acid sequence of Vg in P. vannamei showed high identities of 57% and 78% with those from M. rosenbergii and P. monodon, respectively. The same location of the intron in the sequenced region of genomic DNA was also found between these three species. We therefore concluded that the hepatopancreas and ovary are sites of vitellogenin synthesis in P. vannamei. The partial structure of the vitellogenin gene is further presented.