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Russet on apple fruits was caused by inoculation with isolates of Aureobasidium pullulans and Rhodotorula glutinis but not with Metschnikowia pulcherrima or two other unidentified yeasts, YT2 and YT17. Another unidentified yeast, YT5, caused russet in 1 of 2 years. Epiphytic survival of isolates on fruit was measured 3 months after inoculation. All isolates that caused russet survived epiphytically on fruit at harvest. With the exception of M. pulcherrima, nonrusseting isolates were not detected on the fruit at harvest. Conidia, hyphae, and chlamydospores characteristic of A. pullulans were observed in naturally russeted tissues of 14 different apple cultivars and Bartlett and Bosc pear collected from 13 orchards in New York state. A. pullulans was the most commonly isolated microorganism, and all A. pullulans isolates caused apple russet but varied in the severity of russet they caused. Isolates were identified using standard identification schemes. In addition, A. pullulans isolates were compared by generating fingerprints of restriction fragments of a PCR-amplified region of ribosomal DNA consisting of ITS-1, the 5.8S gene, and ITS-2.

Agrobacterium vitis was isolated from roots of 41 of 66 feral Vitis riparia vines collected in three different regions of New York State. Two of the regions were more than 150 km from commercial vineyards. The strains were highly diverse as determined by DNA fingerprinting of the chromosomal region lying between the 16S and 23S rRNA genes. Of 24 strains examined, 15 different fingerprints were generated, and none was identical to fingerprints generated by previously identified groups of tumorigenic A. vitis strains. Results of physiological tests that were done to characterize strains from V. riparia conformed closely to those expected for A. vitis, except that 23 of 26 strains did not utilize tartrate. All strains were nontumorigenic, did not hybridize with a probe consisting of T-DNA genes, did not utilize octopine or nopaline, and carried zero to three plasmids. Of 26 strains, 7 inhibited A. vitis strain K306 from causing galls at wound sites on grape as well as or better than a previously studied nontumorigenic A. vitis strain, F2/5, that is known to have biological control activity.

Streptomycin is currently the only antibiotic registered for the control of fire blight, a devastating disease of apple (Malus), pear (Pyrus), and other rosaceous plants caused by the bacterium Erwinia amylovora. Resistance of E. amylovora to streptomycin was first identified in California pear orchards in 1971 and is currently endemic in many parts of the United States. The Northeast remains the only major U.S. apple-growing region without streptomycin-resistant isolates of E. amylovora. In 2002, during a routine survey for streptomycin resistance, isolates from two neighboring orchards in Wayne County, NY were found to be highly resistant to streptomycin at a concentration of 100 μg/ml. This constitutes the first authenticated report of streptomycin resistance in New York State. Infected trees were shipped at the same time from a single nursery in Michigan. Resistance was caused by the acquisition of the strA-strB gene pair, inserted into the ubiquitous nontransmissible E. amylovora plasmid pEA29. Previously, streptomycin-resistant E. amylovora populations from Michigan were described with a similar mechanism of resistance, although the strA-strB genes are not unique to Michigan. These findings illustrate how unintentional movement of nursery material could undermine efforts to prevent the spread of antibiotic-resistant E. amylovora.

Agrobacterium vitis, the cause of crown gall disease on grapevine, survives internally in vines and can be spread in cuttings for propagation. The possibility of generating pathogen-free vines through tissue culture makes it essential to understand the distribution of the pathogen in grapevines. A highly sensitive magnetic capture hybridization procedure along with real-time polymerase chain reaction were used to measure the distribution of tumorigenic A. vitis in dormant canes and green shoots of grapevines. Tumorigenic A. vitis was distributed from the basal to apical nodal and internodal tissues of canes as well as in nonlignified green shoots. In experiments conducted in 2013, A. vitis was detected in up to 17% of shoot tips and 52% of meristems of greenhouse-grown plants initiated from known A. vitis-contaminated cuttings. A lower frequency of detection was observed from surface-disinfected shoot tips (7%) as compared with nondisinfected tips (37%), suggesting epiphytic survival on green tissues. In 2014, vines propagated from cuttings collected from crown gall-infected vines from a different vineyard yielded lower incidences of A. vitis from shoot tips, and the bacterium was not detected in meristems. Tumorigenic A. vitis was also detected in cuttings of wild grapevines (Vitis riparia) that were collected both adjacent to and far removed from commercial vineyards.

The effects of tumorigenic and nontumorigenic strains of Agrobacterium vitis on graft strength and growth of grapevines was studied. A procedure was developed for inoculating graft interface surfaces with A. vitis and for measuring the force required to break grafts at different time points. Cuttings were soaked in an aqueous suspension of bacteria, about 106 CFU/ml, and bacteria were spread onto the graft interface during the grafting procedure. Tumorigenic strain CG49 caused reduced bud germination and increased callus (crown gall) at the graft union and at the base of cuttings at 30 days postinoculation (dpi) and significantly reduced shoot growth by 60 dpi whereas, at the same time points, nontumorigenic strain F2/5 inhibited callus formation but did not affect bud germination or shoot growth. Graft strength was enhanced at 30 dpi with CG49, presumably because the crown gall callus served to secure the union; graft strength was weakened by F2/5 over the same period. Between 30 and 60 dpi, the greatest increase in graft strength was observed in the water control. Following graft union inoculations, the A. vitis population increased more than 1,000-fold within 5 days.

Following the 2006 annual meeting of The American Phytopathological Society (APS), President Jan Leach appointed an ad hoc committee with the following charge: Based on an assessment of where plant pathology now stands as a profession, develop a vision of where we will be in the future (10-20 yrs) and how we should position ourselves to achieve this vision. Some key questions and background related to this topic include: (1) Disciplinary Balance (2) Institutional Erosion (3) Research Funding and (4) Age Demographics of the Profession. The year following the 100th birthday of APS seems an especially opportune time to take stock of where we stand as a discipline, to identify near-term and long-term challenges, and to discuss how we might meet those challenges in the future. Indeed, the present state and future prospects of our discipline have been recurrent themes of reviews, letters, and editorials from generations of plant pathologists (4,10–17). Most have reflected the experiences and the scholarly but nonetheless personal viewpoint of a single author. What was often lacking were the hard data that would support the stated positions when applied to the discipline as a whole. This report summarizes the efforts of the APS Ad Hoc Committee on the Present Status and Future of the Profession of Plant Pathology to address the above charge. We have attempted to rely upon a dispassionate methodology and go where the data lead us. Our approach has been to study key events and trends of the last several decades at the national level, assemble a base of information from which to properly understand the issues, and attempt to identify and project future trends and challenges facing the profession. Only then would we be in a position to develop recommendations for the profession to meet such challenges. A complete census of plant pathology at U.S. universities, conducted by the Ad Hoc Committee in 2007, formed the foundation for these analyses. Census of plant pathology at U.S. universities. Although both APS and the National Science Foundation (NSF) collect various statistics on departments and sample survey data on graduate degrees in plant pathology, we are not aware of any recent census of plant pathology at U.S. universities. A census differs from a survey in that the aim is to measure an entire population rather than rely upon a statistical sample. A complete and accurate assessment of the number of active plant pathology faculty at U.S. universities, the size of the graduate student population, and membership of both groups in APS was an essential precursor to any demographic analysis. We collected the following responses: (i) the total number of faculty in a department, (ii) the number of plant pathology faculty in the department in the case of multidisciplinary departments (such as plant science or entomology and plant pathology), (iii) the number of faculty who belonged to APS, (iv) the number of faculty who held doctoral degrees in plant pathology, (v) the total number of M.S. and Ph.D. students in the department (some of whom may be pursuing degrees in areas other than plant pathology), and (vi) the number of plant pathology graduate students (both M.S. and Ph.D.). The data were collected by repeatedly sending a blank spreadsheet to department chairs, former students, postdocs, and colleagues across the United States. Missing data were obtained from department websites and the APS member database. All 1862 and 1890 Land Grant institutions were included in the census. Additional plant pathology faculty and students outside the aforementioned systems were located by searching the APS membership database for faculty and student affiliations. Plant pathology faculty, as well as plant patholCorresponding author: David M. Gadoury, Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Geneva, NY; E-mail: dmg4@nysaes.cornell.edu

Agrobacterium vitis was recovered from living and decaying grape roots and canes 23 months after grapes were artificially inoculated with a mixture of six strains of the bacterium. Each strain contained a unique plasmid profile. Following inoculation, some plants were treated with the herbicide Roundup to speed up plant death and tissue decay. Roots and canes were assayed over time, and by comparing plasmid profiles of recovered strains it was determined that certain A. vitis strains used in the inoculum mixture were recovered more frequently than others. Profiles identical to those identified for each strain used in the inoculum mixture were observed at least twice in strains recovered during the experiment. Of 133 plasmid profiles that were observed, only 18 did not resemble any of the strains used in the inoculum mixture. Of 333 strains recovered from roots and canes, 321 were tumorigenic, indicating that this trait was stable throughout the experiment. A group of six strains having plasmid profiles identical to strain CG49 that were recovered over an 16-month period were further characterized using restriction fragment length polymorphic analysis of plasmid DNA, random amplified polymorphic DNA analysis of total genomic DNA, and ribofingerprinting of a chromosomal region including 1,479 bp (99.5%) of the 16S rDNA, the intergenic spacer between 16S and 23S rDNA genes, and 132 bp of the 23S rDNA gene. All six strains were shown to be identical to CG49.

Resultats des essais d'evaluation des mesures de lutte contre Nectria cinnabarina sur pommiers