Genetic diversity and infection sources of Rosellinia necatrix in northern Israel

Symptoms of white root rot (caused by Rosellinia necatrix) of fruit trees (including apple, cherry and peach) are rotting of the roots and yellowing of the leaves, followed by wilting and death. Undecomposed organic material in forest soils is favourable for growth of R. necatrix. Genetic tools and mycelial compatibility assays can be used to group the fungus into genetically similar groups. This study identified and located the sources of root infection, using broad surveys of infested plots in various locations, and assessed infection probability as a function of distance from potential inoculum source. Fifty-five infested plots in 14 settlements at different altitudes were surveyed. About 60% of the infested plots, at altitudes up to 540 m above sea level, were located near Mediterranean oak maquis forests, and the infections spread inward from the edges of the fruit orchards. These results indicated four possible sources of infection: (i) Mediterranean maquis forest near agricultural lands; (ii) soil transferred to low-lying sections within orchards; (iii) infection source carried by farmers from plots on the same farm; and (iv) infections via roots of adjacent trees within orchards. No correlation was found between genetic variation and virulence, but isolates that grew quickly on potato dextrose agar plates at 28oC were more virulent than slow growing isolates

Biological systems of the host cell involved in Agrobacterium infection

Genetic transformation of plants by Agrobacterium , which in nature causes neoplastic growths, represents the only known case of trans -kingdom DNA transfer. Furthermore, under laboratory conditions, Agrobacterium can also transform a wide range of other eukaryotic species, from fungi to sea urchins to human cells. How can the Agrobacterium virulence machinery function in such a variety of evolutionarily distant and diverse species? The answer to this question lies in the ability of Agrobacterium to hijack fundamental cellular processes which are shared by most eukaryotic organisms. Our knowledge of these host cellular functions is critical for understanding the molecular mechanisms that underlie genetic transformation of eukaryotic cells. This review outlines the bacterial virulence machinery and provides a detailed discussion of seven major biological systems of the host cell–cell surface receptor arrays, cellular motors, nuclear import, chromatin targeting, targeted proteolysis, DNA repair, and plant immunity – thought to participate in the Agrobacterium -mediated genetic transformation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75425/1/j.1462-5822.2006.00830.x.pd

Tracking the dissemination of Erwinia amylovora in the Eurasian continent using a PCR targeted on the duplication of a single CRISPR spacer

Fire blight is the most devastating disease affecting pome fruit production globally. The pathogen is native to North America and was imported to western Europe in the 1950s, progressively spreading over the continent in the ensuing decades. Previous phylogenetic studies have revealed the extreme genetic homogeneity of the pathogen outside its center of origin, which makes epidemiological studies difficult. These are generally only possible using hypervariable regions of the genome such as those represented by CRISPRs (Clustered Regularly Interspaced Short Palindromic Repeats), which are, however, not practical to sequence due to their size and variability. Here, we present a simple PCR assay targeting the duplication of a single CRISPR spacer in Erwinia amylovora that was found to be an important marker to discriminate between two main European populations of the pathogen. We implemented the assay on a total of 582 isolates to follow the spread of fire blight across the continent over several decades and, wherever possible, within single countries. The results obtained point to the occurrence of two major separate introduction events for E. amylovora in Europe that occurred approximately 20 years apart, and confirmed the existence of two principal distribution areas located in Northeastern Europe and the Eastern Mediterranean Basin from which the pathogen moved on to colonize the Eurasian continent

Flower proteome: changes in protein spectrum during the advanced stages of rose petal development

Flowering is a unique and highly programmed process, but hardly anything is known about the developmentally regulated proteome changes in petals. Here, we employed proteomic technologies to study petal development in rose ( Rosa hybrida ). Using two-dimensional polyacrylamide gel electrophoresis, we generated stage-specific (closed bud, mature flower and flower at anthesis) petal protein maps with ca. 1,000 unique protein spots. Expression analyses of all resolved protein spots revealed that almost 30% of them were stage-specific, with ca. 90 protein spots for each stage. Most of the proteins exhibited differential expression during petal development, whereas only ca. 6% were constitutively expressed. Eighty-two of the resolved proteins were identified by mass spectrometry and annotated. Classification of the annotated proteins into functional groups revealed energy, cell rescue, unknown function (including novel sequences) and metabolism to be the largest classes, together comprising ca. 90% of all identified proteins. Interestingly, a large number of stress-related proteins were identified in developing petals. Analyses of the expression patterns of annotated proteins and their corresponding RNAs confirmed the importance of proteome characterization.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47485/1/425_2005_Article_1512.pd

Genetic diversity and infection sources of <em>Rosellinia necatrix</em> in northern Israel

Symptoms of white root rot (caused by Rosellinia necatrix) of fruit trees (including apple, cherry and peach) are rotting of the roots and yellowing of the leaves, followed by wilting and death. Undecomposed organic material in forest soils is favourable for growth of R. necatrix. Genetic tools and mycelial compatibility assays can be used to group the fungus into genetically similar groups. This study identified and located the sources of root infection, using broad surveys of infested plots in various locations, and assessed infection probability as a function of distance from potential inoculum source. Fifty-five infested plots in 14 settlements at different altitudes were surveyed. About 60% of the infested plots, at altitudes up to 540 m above sea level, were located near Mediterranean oak maquis forests, and the infections spread inward from the edges of the fruit orchards. These results indicated four possible sources of infection: (i) Mediterranean maquis forest near agricultural lands; (ii) soil transferred to low-lying sections within orchards; (iii) infection source carried by farmers from plots on the same farm; and (iv) infections via roots of adjacent trees within orchards. No correlation was found between genetic variation and virulence, but isolates that grew quickly on potato dextrose agar plates at 28oC were more virulent than slow growing isolates