Morpho-colorimetric characterisation of Malva alliance taxa by seed image analysis.

Seed morphometric and -colorimetric features describing shape, size and textural seed traits of 28 taxa belonging to the genera Lavatera L. and Malva L., were recorded by means of computer vision techniques. The data were statistically analysed to contribute to the taxonomical treatment of the Malva alliance and to assess some doubtful systematic positions. A clear differentiation between taxa traditionally attributed to Lavatera or Malva was highlighted. Furthermore, the identification system proposed here was able to discriminate among the Lavatera sections, confirming the taxonomic organization of this genus. The results obtained for Malva, both at the species level and among sections, supported this analytical tool as diagnostic for systematic purposes.

Malvone A, a phytoalexin found in Malva sylvestris (family Malvaceae).

The isolation and structure of a phytoalexin, malvone A (2-methyl-3-methoxy-5,6-dihydroxy-1,4-naphthoquinone) is reported. Malvone A formation is induced in Malva sylvestris L. by the plant pathogen Verticillium dahliae. In a turbimetric assay for toxicity to V. dahliae, it had an ED50 value of 24 microg/ml. The structure of malvone A was determined by MS and NMR spectroscopy, and by X-ray crystallographic analysis. The X-ray analysis showed water molecules were located in channels that run along the a-axis.

Species identification of plant tissues from the gut of An. sergentii by DNA analysis.

There are three commonly used assays to identify plant material in insect guts: the cold anthrone test for fructose, the cellulose staining test for visualizing plant tissue and gas chromatography for seeking unique sugar content profiles. Though sugar and cellulose tests can distinguish between the general sources of sugar meal (nectar versus tissue), they cannot identify the species of plant sources. Even gas chromatography profiles can be problematic; there are reported instances of intra-specific variation as well as inter-specific and intergeneric variation that can mar results. Here, we explore the potential for DNA analysis to help resolve this issue. First, Anopheles sergentii were exposed to branches of two species of highly attractive flowering bushes in the laboratory and the great majority ( approximately 90-98%) were positive for sugar from nectar while very few were positive for cellulose ( approximately 0.5-8%) and DNA (6-19%). Moreover, laboratory An. sergentii showed opposing preferences, tending to obtain sugar from nectar of one plant (Tamarix nilotica) but to feed more on tissue from the other (Ochradenus baccatus). An. sergentii are exposed to a wide variety of plants in their natural desert habitats and in the absence of flowers in the dry season, they resort to feeding specifically on tissues of a few plants. According to DNA analysis the favorite plants were Suaeda asphaltica, Malva nicaeensis and Conyza dioscoridis, which are succulents that account for less than 1% of vegetation in the area.