Worldwide diffusion of Fig latent virus 1 in fig accessions and its detection by serological and molecular tools

A virus with filamentous particles ca. 700 nm long, denoted Fig latent virus 1 (FLV-1) is widespread in Apulian (southern Italy) fig orchards, in trees showing or not mosaic symptoms and in symptomless seedlings. The virus was transmitted by sap inoculation to a very restricted range of herbaceous hosts without inducing apparent symptoms and was transmitted through fig seeds to a very high percentage (80 to 100 %). It was successfully purified from root tissues of infected figs. A virus-specific antiserum raised in rabbits, proved useful for its detection in fig leaf dips by immunosorbent electron microscopy (ISEM), Western Blot, dot immuno-binding (DIBA), ELISA. The viral genome structure resembles that of members of the genus Trichovirus in the family Flexiviridae. Keywords: fig latent virus, Trichovirus, serology, ISEM, Western blot, DIBA, ELIS

The impact of xylem geometry on olive cultivar resistance to Xylella fastidiosa: an image‐based study

Xylella fastidiosa is a xylem-limited plant pathogen infecting many crops globally and is the cause of the recent olive disease epidemic in Italy. One strategy proposed to mitigate losses is to replant susceptible crops with resistant varieties. Several genetic, biochemical and biophysical traits are associated to X. fastidiosa disease resistance. However, mechanisms underpinning resistance are poorly understood. We hypothesize that the susceptibility of olive cultivars to infection will correlate to xylem vessel diameters, with narrower vessels being resistant to air embolisms and having slower flow rates limiting pathogen spread. To test this, we scanned stems from four olive cultivars of varying susceptibility to X. fastidiosa using X-ray computed tomography. Scans were processed by a bespoke methodology that segmented vessels, facilitating diameter measurements. Though significant differences were not found comparing stem-average vessel section diameters among cultivars, they were found when comparing diameter distributions. Moreover, the measurements indicated that although vessel diameter distributions may play a role regarding the resistance of Leccino, it is unlikely they do for FS17. Considering Young–Laplace and Hagen–Poiseuille equations, we inferred differences in embolism susceptibility and hydraulic conductivity of the vasculature. Our results suggest susceptible cultivars, having a greater proportion of larger vessels, are more vulnerable to air embolisms. In addition, results suggest that under certain pressure conditions, functional vasculature in susceptible cultivars could be subject to greater stresses than in resistant cultivars. These results support investigation into xylem morphological screening to help inform olive replanting. Furthermore, our framework could test the relevance of xylem geometry to disease resistance in other crops

Presenza di un ceppo necrogenico di Watermelon mosaic virus in colture di melone giallo in Sicilia

Viene descritta una sintomatologia di tipo necrotico osservata su piante e frutti di melone “gialletto” coltivate nella Sicilia occidentale. Nelle piante infette è stata riscontrata la presenza di Watermelon mosaic virus (WMV) ma non quella di Zucchini yellow mosaic virus, di Papaya ringspot virus o di virus con particelle sferiche. Ancorché basata su dati preliminari, l’indagine suggerisce che nell’eziologia della malattia sia coinvolto un isolato necrogenico di WMV, denominato WMV-Si

Molecular caracterization and phylogenetic analysis of Turnip moasic virus (TuMV) in Erysimum linifolium L. in Italy

In the Summer of 2012, Erysimum linifolium L. pot plants produced at an ornamental grower in Liguria region (northern Italy), showed unusual virus-like disease of dark mottle and stripes on mauve-purple petals. A virus was mechanically transmitted from symptomatic flowers to several test plant species belonging to Chenopodiaceae and Brassicaceae families. This virus was identified as an isolated of turnip mosaic virus (TuMV) by PAS-ELISA analysis, electron microscopy negatively stained crud extracts and immuno-electron microscopy (IEM) tests. In the naturally infected E. linifolium plants, TuMV occurred alone, since any other viruses either by electron microscopy or mechanical inoculations were detected. By applying RT-PCR a fragment of 862 bp was amplified corresponding to all coat protein (CP). The comparison of CP gene showed no correlations between their genetic variation and geographical origins. The diversity in southern Europe appeared very low, most likely due to the rapid growth of TuMV in relation to trade between different Countries. The consequent exchange of infected propagation material shows that some lineages are adapted to particular crop species, and that recombination is a significant generator of the genetic diversity in populations of this virus. This is the first report of TuMV in E. linifolium worldwide