Agrobacterium strain specificity and shooty tumour formation in eucalypt (Eucalyptus grandis ×E. urophylla)

Summary To develop a successful protocol forAgrobacterium-mediated transformation in plants it is essential to determine the most efficient bacterial strain/plant genotype interaction. In the present work, we evaluated the susceptibility ofEucalyptus grandis ×E. urophylla to fiveAgrobacterium rhizogenes and twelveA. tumefaciens wildtype strains. The results showed different degrees of virulence, according to the strain tested, indicating that transformation of this eucalypt hybrid by Agrobacterium-derived vectors is possible. All developed tumours showed an autonomous growth when transferred to a hormone-free medium. Some of these tumours formed shoots spontaneously, with a normal phenotype. Polymerase Chain Reaction (PCR) and Southern blot analyses were performed to confirm the absence of the oncogenic T-DNA in plants derived from these shooty tumours.     

Development of a ploidy series from a single interspecific Trifolium repens L.Ā . nigrescens Viv. F1 hybrid

 The objective of the current research was to generate a ploidy series of backcross progenies from a single triploid (2n=3x=24) Trifolium repens×T. nigrescens F₁ hybrid (3x H-6909-5). The 3x H-6909-5 plant was highly sterile and produced no seeds from approximately 3000 reciprocal backcrosses to both parental species. Chromosome doubling by an in vitro colchicine method resulted in a marked increase in fertility. Pollen stainability was increased from 9.9% in 3x H-6909-5 to an average of 89.2% (range 87.7–90.9%) in the three chromosome-doubled 6x H-6909-5 plants. Subsequent backcrosses of 6x H-6909-5 and interbreeding of backcross derivatives resulted in an array of fertile hybrids at 4x, 5x and 7x levels and some aneuploids. The occurrence of 7x BC₁F₁ progeny from the T. repens×6x H-6909-5 (4x×6x) cross is the first unequivocal evidence of functional female 2n gametes in white clover. Meiotic pairing in F₁ and BC₁F₁ progeny indicated the presence of allosyndetic pairing, suggesting that genetic exchange between the two species is possible. Received: 17 October 1996 / Accepted: 8 November 1996     

Viral diseases of penaeid shrimp with particular reference to four viruses recently found in shrimp from Queensland

The culture of penaeid shrimp world-wide is primarily dependent on wild-caught broodstock which has an enormous potential to introduce new pathogens, particularly viruses, into culture systems. Of the 13 viruses described for cultured penaeid shrimp, seven have been described within the past 5 years; the most devastating viral epidemics on record for cultured penaeid shrimp have also occurred within the past 5years. During examination of local wild and cultured shrimp, four new viruses were found. Bennettae baculovirus was discovered in the digestive gland of wild Metapenaeus bennettae. It closely resembles monodon baculovirus (MBV) but has a more slender virion, does not cross-react with a DNA probe for MBV and is not infectious to Penaeus monodon. Two morphologically indistinguishable viruses, one pathogenic (gill-associated virus, GAV) and the other benign (lymphoid organ virus, LOV), were found in cultured P. monodon. LOV and GAV closely resemble yellow head virus (YHV) of Thailand. A parvo-like virus was found recently in dying post-larvae of P. japonicus. As the intensity of shrimp culture world-wide increases, researchers can expect to discover more penaeid viruses. The need to close the life cycle of P. monodon and other cultured species and develop rapid diagnostic methods for viral infections has become imperative.     

Molecular mimicry of host structures by bacterial lipopolysaccharides and its contribution to disease

Abstract The core oligosaccharides of low-molecular-weight lipopolysaccharide (LPS), also termed lipooligosaccharide (LOS), of pathogenic Neisseria spp. mimic the carbohydrate moieties of glycosphingolipids present on human cells. Such mimicry may serve to camouflage the bacterial surface from the host. The LOS component is antigenically and/or chemically identical to lactoneoseries glycosphingolipids and can become sialylated in Neisseria gonorrhoeae when the bacterium is grown in the presence of cytidine 5′-monophospho- N -acetylneuraminic acid, the nucleotide sugar of sialic acid. Strains of Neisseria meningitidis and Haemophilus influenzae also express similarly sialylated LPS. Sialylation of the LOS influences susceptibility to bactericidal antibody, may decrease or prevent phagocytosis, cause down-regulation of complement activation, and decrease adherence to neutrophils and the subsequent oxidative burst response. The core oligosaccharides of LPS of Campylobacter jejuni serotypes which are associated with the development of the neurological disorder, Guillain-Barré syndrome (GBS), exhibit mimicry of gangliosides. Cross-reactive antibodies between C. jejuni LPS and gangliosides are considered to play an important role in GBS pathogenesis. In contrast, the O-chain of a number of Helicobacter pylori strains exhibit mimicry of Lewis^x and Lewis^y blood group antigens. The role of this mimicry remains to be investigated, but may play a role in bacterial camouflage, the induction of autoimmunity and immune suppression in H. pylori -associated disease.     

The effect of a water gradient on the vesicular-arbuscular mycorrhizal status of Lythrum salicaria L. (purple loosestrife)

 The mycorrhizal status of Lythrum salicaria (Lythraceae) was assessed under growth room and field conditions. Growth room studies indicated that L. salicaria is facultatively mycorrhizal and capable of forming vesicular-arbuscular associations with six Glomus species, but not with Gigaspora margarita. Overall, hyphal and arbuscular colonization levels were significantly higher in the wet treatments than in the dry treatments (P<0.0001). However, taken individually, significant increases in arbuscular colonization (P<0.05) were found only in L. salicaria colonized with Glomus clarum, G. aggregatum, and G. versiforme and exposed to the wet treatments compared with the dry treatments, while significant increases in hyphal colonization were found in L. salicaria colonized with G. clarum, and G. versiforme exposed to the wet treatments. There was no overall effect of water availability on levels of vesicular colonization or differences in vesicular colonization levels within species under dry or wet conditions. In contrast, field studies along an existing water gradient revealed that hyphal and arbuscular colonization levels were significantly higher (P<0.05) in the dry and intermediate regions of the gradient than in the wet regions. Vesicular colonization was not significantly affected by the gradient. Total stem height was significantly affected by water availability, plot location and an interaction of the two (P<0.05), and was generally higher in the intermediate and wet plots. Accepted: 20 September 1995     

Molecular phylogeny and DNA amplification fingerprinting of Petunia taxa

The relationship of five species of Petunia and ten cultivars of the cultivated petunia, Petunia x hybrida, were investigated using DNA-amplification fingerprinting (DAF). Reproducible banding profiles were obtained from P. parodii and P. axillaris DNA from different seed sources. In contrast, other petunias such as P. inflata, P. violacea and P. integrifolia produced variable fingerprints when different plants were examined. However, representative profiles of the variable Petunia taxa were obtained by bulking the leaf tissue from ten different individual plants. Each of ten octamer primers revealed polymorphic loci between taxa. Among a total of 201 bands produced, 146 (73%) loci were polymorphic and distinguished all species and cultivars. Phenetic and cluster analysis using DAF markers separated P. axillaris from P. parodii and distinguished between the violet-flowered species, P. inflata, P. violacea, and P. integrifolia. P. parodii grouped together with the monophyletic set of the ten cultivars of P. x hybrida examined, indicating that it had made a major contribution to the development of these cultivars. Cultivars were distributed within the dendograms by flower color. The results demonstrated the utility of DAF in establishing relationships among closely related species and cultivars of Petunia.     

柴胡类药材的柴胡皂甙分析

柴胡类药材的柴胡皂甙分析李光慧罗燕燕王瑛袁昌齐王年鹤（北京临床药学研究所,北京１０００３５）（江苏省中国科学院植物研究所,南京２１００１４）ＡｎａｌｙｓｉｓｏｆｓａｉｋｏｓａｐｏｎｉｎｓｉｎｍｅｄｉｃｉｎａｌＢｕｐｌｅｕｒｕｍｓｐｐ．ＬｉＧｕａｎｇ...     

Effects of intercropping white cabbage with clovers on pest infestation and yield

During two consecutive years the effects of intercropping fresh market white cabbage with two species of clover on pest populations and yield were studied. White cabbage cv. Minicole was intercropped withTrifolium repens (white clover) andTrifolium subterraneum (subterranean clover) as compared to the monocrop. During the season observations were made on pest population developments, especially ofMamestra brassicae L. (cabbage moth),Brevicoryne brassicae L. (cabbage aphid),Delia brassicae L. (cabbage root fly), and evaluation of caterpillar feeding injury. At harvest the yield in quantity and quality was determined to be able to assess the gross financial result. Intercropping effects in terms of suppression of oviposition and larval populations of various pests were found. Although no pesticides were used and competition reduced the weight, the quality of the intercropped cabbages lead to a better financial result compared to the monocropped cabbage crop. The results are discussed in the perspective of the practical implications in the context of IPM.     

Competition between mullet fry

The fry of Liza ramada, L. aurata, L. saliens, Chelon labrosus and Mugil cephalus in a lagoon in NE Spain fed mainly on zooplanktonic crustacea, such as cyclopoids, calanoids and cladocerans, but adult chironomids were also important. A high trophic and temporal overlap was found between the fry of several of these species. Trophic overlap was asymmetrical for almost all the species pairs and niche breadth expanded for the less competitive species when they were alone in the estuary. In contrast, niche breadth did not expand for the most competitive species ( L. ramada ) when it was alone. These results suggest that competition was occurring among these species, but experimental evidence is needed to prove its existence.     

TWO NEW SPECIES OF TAYLORIELLA (RHODOMELACEAE,RHODOPHYTA) FROM THE NORTHEASTERN NORTH PACIFIC1

Two new species are recognized in the rhodomelacean genus Tayloriella Kylin: T. divaricata sp. nov. and T. abyssalis sp. nov. These two taxa are distributed in the northeastern North Pacific, the former ranging from Amchitka Island in the Aleutians through southcentral Alaska to northern British Columbia, and the latter ranging also from Amchitka Island through southcentral Alaska and British Columbia into northern Washington. A characteristic of these two species shared with the type of Tayloriella is that the abaxial lateral always overtops the monopodially developed axes in every order of branching. The laterals have little congenital fusion with the parent axes. A common feature in these two species is that the laterals are terminated in a relatively long monosiphonous portion (usually 6 or 7 cells). The relationship of Tayloriella to Pterosiphonia and Pterosiphoniella is discussed.