Using the Indian medicinal plant Tulsi (Holy Basil) as a case study, we have tested to what extent the discrepancy between vernacular and scientific nomenclature can be resolved, whether the presumed chemical diversity underlying the medicinal use of Tulsi has a genetic component, and whether it is possible to detect this genetic component using genetic barcoding markers. Based on four plastidic markers, we can define several haplotypes within Ocimum that are consistent across these markers. Haplotype II is congruent with O. tenuiflorum, while haplotype I extends over several members of the genus and cannot be resolved into genetically separate subclades. The vernacular subdivision of Tulsi into three types (Rama, Krishna, Vana) can only be partially linked with genetic differences–whereby Rama and Krishna Tulsi can be assigned to O. tenuiflorum, while Vana Tulsi belongs to haplotype I. This genetic difference is mirrored by differences in the profiles of secondary compounds. While developmental state and light quality modulate the amplitude to which the chemical profile is expressed, the profile itself seems to be linked with genetic differences. We finally develop an authentication assay that makes use of a characteristic single nucleotide polymorphism in one of the barcoding markers, establishing a differential restriction pattern that can be used to discriminate Vana Tulsi.

In order to obtain insight into host responses to grapevine downy mildew (Plasmopara viticola), we compared pathogen development on a panel of Vitis species from North America, Asia and Europe. Leaf discs from different host species were inoculated in parallel, and the colonisation of the mesophyll was visualised by aniline blue staining and quantified with respect to infection incidence and mycelial growth. In parallel, the morphology of guard cells was screened for the presence of an internal cuticular rim after staining with acridine orange and using low-temperature scanning electron microscopy. We observed three response patterns: (i) inhibition of pathogen development early after attachment of zoospores; (ii) successful colonisation of the mesophyll by the pathogen; and (iii) aberrant development, where the pathogen does not attach to guard cells, but produces hyphae on the leaf surface without formation of viable sporangiophores. Inhibition is observed in the North American and Siberian species, successful colonisation prevails in the European hosts, and surface hyphae are found on non-Siberian Asiatic species. We propose that the interaction between host and pathogen is under control of specific signals that have been subject to evolutionary diversification.

No abstract

Lemon Myrtle' is becoming increasingly popular in Europe both for use in cuisine and phytotherapy. However, this common name covers two completely diVerent species, Backhousia citriodora F. Muell. and Leptospermum citratum Challinor, Cheel & A.R.Penfold. These species diVer with respect to secondary compounds and even can cause, if mixed up and applied in high dose, toxic eVects. We describe how the two species can be discriminated microscopically making use of diVerences in the morphology of leaf pavement cells and the relative size of palisade parenchyma. Based on the large subunit of ribulose-1,5-bisphosphate carboxylase oxygenase (rbcL) as molecular marker, the phylogenetic position of the two species within the Myrtaceae could be clariWed. This sequence information was used to develop a simple assay to discriminate the two species even in dried and highly fragmented mixtures as typically occurring in commercial samples. This assay utilises the occurrence of single-nucleotide exchanges between those species that produce diVerent fragments when the rbcL ampliWcates are restricted with Sac II.

It recently became clear that adult eo- and palaeacanthocephalans parasitizing fish can bioconcentrate several heavy metals to significantly higher concentrations than the tissues of their definitive hosts. Following this discovery the lead accumulation of the archiacanthocephalan Moniliformis moniliformis was investigated using experimentally infected male Wistar rats of the CD-M-strain. The worms were allowed to grow up for 4 weeks post-infection followed by a 3 weeks oral lead exposure of the rats. After the exposure period the rats were killed and the metal levels were determined in muscle, liver, intestine and kidney of the rats as well as in different organs of female and male acanthocephalans. Lead concentrations were found to be highest in female M. moniliformis followed by the kidneys of the rats. Male worms contained approximately the same lead concentration as the hosts' kidneys. Lead analysis of the worms' organs revealed the highest lead concentration in the eggs of female acanthocephalans, followed by the cement gland of male Worms. Whilst the lead burden of the presoma was higher than that detected in the kidneys of the rats, the lead content of the metasoma was even lower than in the kidneys. A lead uptake of M. moniliformis from the intestinal lumen of the host became apparent as the faeces of infected rats contained significantly less lead compared to the uninfected conspecifics. Thus, this study reveals that lead accumulation also occurs in archiacanthocephalans parasitizing mammals. But the degree of metal bioconcentration is considerably lower compared to eo- and palaeacanthocephalans in fish. Anyway, due to a lack of adequate sentinel species in terrestrial biotopes the host-parasite system rat M. moniliformis appears to be a useful and promising bioindication system especially in urban ecosystems in temperate regions.