Stable expression and phenotypic impact of attacin E transgene in orchard grown apple trees over a 12 year period

<p>Abstract</p> <p>Background</p> <p>Transgenic trees currently are being produced by <it>Agrobacterium</it>-mediated transformation and biolistics. The future use of transformed trees on a commercial basis depends upon thorough evaluation of the potential environmental and public health risk of the modified plants, transgene stability over a prolonged period of time and the effect of the gene on tree and fruit characteristics. We studied the stability of expression and the effect on resistance to the fire blight disease of the lytic protein gene, <it>attacin E</it>, in the apple cultivar 'Galaxy' grown in the field for 12 years.</p> <p>Results</p> <p>Using Southern and western blot analysis, we compared transgene copy number and observed stability of expression of this gene in the leaves and fruit in several transformed lines during a 12 year period. No silenced transgenic plant was detected. Also the expression of this gene resulted in an increase in resistance to fire blight throughout 12 years of orchard trial and did not affect fruit shape, size, acidity, firmness, weight or sugar level, tree morphology, leaf shape or flower morphology or color compared to the control.</p> <p>Conclusion</p> <p>Overall, these results suggest that transgene expression in perennial species, such as fruit trees, remains stable in time and space, over extended periods and in different organs. This report shows that it is possible to improve a desirable trait in apple, such as the resistance to a pathogen, through genetic engineering, without adverse alteration of fruit characteristics and tree shape.</p

Measuring Applied Antagonistic Bacterial Populations for Management of Fire Blight within the State of New York

The blossom blight phase of fire blight, caused by the bacterium Erwinia amylovora, is typically managed by applying the antibiotic, streptomycin sulfate, to trees during bloom. Biological control of fire blight can be achieved by applying non-pathogenic bacteria to open flowers that then colonize flower part surfaces and compete with the pathogen for space and nutrients. The objective of this study was to measure the growth of three applied biological control organisms at three orchard locations in New York. We hope to identify safe and effective alternatives to streptomycin because the pathogen is likely to become resistant to streptomycin if this product is used too often. This has already occurred in some western and mid-western states. We detected population levels of the biological control organisms that were slightly lower than those reported in the Pacific Northwest. We also determined that the spread of the biological control organisms increased over time at each location. Application of the bacteria with a handgun sprayer appeared to result in higher populations than when applied with a handheld sprayer. A mixture of antagonists was detected at more than one location, indicating either tank contamination or natural dispersal of the organisms via pollinators. Our results confirmed the ability of these three biological control organisms to colonize and multiply on flowers in New York state. Further studies with larger sample sizes would allow us to make stronger correlations between population levels and incidence of the biological control agents, and their ability to prevent disease.

Efficacy of Resistance to Scab in Transgenic ‘McIntosh’ Apple Exposed to Populations of Venturia inaequalis

ReportMcIntosh apples which have been transformed to express an endochitinase gene from Trichoderma harzianum have demonstrated substantial resistance to apple scab in previous greenhouse trials. We inoculated transgenic and control McIntosh trees with ascosporic and conidial inoculum, and recorded disease development and plant growth in a greenhouse and orchard study. In greenhouse evaluations, all transgenic lines developed statistically equivalent levels of scab when compared to the McIntosh control with both inoculum sources. Transgenic trees in the orchard generally had fewer leaves per tree, were shorter, smaller in diameter, and had fewer side branches than the nontransformed control McIntosh early in the growing season. However, this was primarily a reflection of different tree sizes among the transgenic lines and control trees when planted in 1999. With only one exception (TM961), current-season shoot length was not significantly different among the transgenic lines and the control McIntosh. In the orchard, the incidence of scab infection (percentage of leaves infected) on all four transgenic lines (including the vector control) was significantly equivalent to that recorded on the untransformed control McIntosh. However, disease severity (percentage of the leaf surface colonized) was significantly lower on all the transgenic lines

Identification of genes differentially expressed during interaction of resistant and susceptible apple cultivars (<it>Malus × domestica</it>) with <it>Erwinia amylovora</it>

Abstract Background The necrogenic enterobacterium, Erwinia amylovora is the causal agent of the fire blight (FB) disease in many Rosaceaespecies, including apple and pear. During the infection process, the bacteria induce an oxidative stress response with kinetics similar to those induced in an incompatible bacteria-plant interaction. No resistance mechanism to E. amylovora in host plants has yet been characterized, recent work has identified some molecular events which occur in resistant and/or susceptible host interaction with E. amylovora: In order to understand the mechanisms that characterize responses to FB, differentially expressed genes were identified by cDNA-AFLP analysis in resistant and susceptible apple genotypes after inoculation with E. amylovora. Results cDNA were isolated from M.26 (susceptible) and G.41 (resistant) apple tissues collected 2 h and 48 h after challenge with a virulent E. amylovora strain or mock (buffer) inoculated. To identify differentially expressed transcripts, electrophoretic banding patterns were obtained from cDNAs. In the AFLP experiments, M.26 and G.41 showed different patterns of expression, including genes specifically induced, not induced, or repressed by E. amylovora. In total, 190 ESTs differentially expressed between M.26 and G.41 were identified using 42 pairs of AFLP primers. cDNA-AFLP analysis of global EST expression in a resistant and a susceptible apple genotype identified different major classes of genes. EST sequencing data showed that genes linked to resistance, encoding proteins involved in recognition, signaling, defense and apoptosis, were modulated by E. amylovora in its host plant. The expression time course of some of these ESTs selected via a bioinformatic analysis has been characterized. Conclusion These data are being used to develop hypotheses of resistance or susceptibility mechanisms in Malus to E. amylovora and provide an initial categorization of genes possibly involved in recognition events, early signaling responses the subsequent development of resistance or susceptibility. These data also provided potential candidates for improving apple resistance to fire blight either by marker-assisted selection or genetic engineering.</p

, Rosario Provvidenti

Also available as a printed booklet and from the Dean of Faculty website https://theuniversityfaculty.cornell.edu/Memorial Statement for Rosario Provvidenti, who died in 2019. The memorial statements contained herein were prepared by the Office of the Dean of the University Faculty of Cornell University to honor its faculty for their service to the university

Multiple models for Rosaceae genomics

The plant family Rosaceae consists of over 100 genera and 3,000 species that include many important fruit, nut, ornamental, and wood crops. Members of this family provide high-value nutritional foods and contribute desirable aesthetic and industrial products. Most rosaceous crops have been enhanced by human intervention through sexual hybridization, asexual propagation, and genetic improvement since ancient times, 4,000 to 5,000 B.C. Modern breeding programs have contributed to the selection and release of numerous cultivars having significant economic impact on the U.S. and world markets. In recent years, the Rosaceae community, both in the United States and internationally, has benefited from newfound organization and collaboration that have hastened progress in developing genetic and genomic resources for representative crops such as apple (Malus spp.), peach (Prunus spp.), and strawberry (Fragaria spp.). These resources, including expressed sequence tags, bacterial artificial chromosome libraries, physical and genetic maps, and molecular markers, combined with genetic transformation protocols and bioinformatics tools, have rendered various rosaceous crops highly amenable to comparative and functional genomics studies. This report serves as a synopsis of the resources and initiatives of the Rosaceae community, recent developments in Rosaceae genomics, and plans to apply newly accumulated knowledge and resources toward breeding and crop improvement

A proposal for the nomenclature of Venturia inaequalis races

International audienceThe Venturia inaequalis-Malus pathosystem was one of the first for which gene-for-gene relationships were demonstrated following the discovery of such relationships between Melampsora lini and flax by Flor in the 1950s. An understanding of these relationships forms the basis for monitoring pathotypes of V. inaequalis at the population level and is employed to assess the usefulness of resistance genes for breeding durable resistance to scab. These pathotypes are difficult to accommodate in the current system of nomenclature for V. inaequalis races where each new combination of avirulence alleles is assigned a simple numerical descriptor as its name. We propose a system that is better suited to the increasing complexities of combinations of genes involved in both race-specific and race-nonspecific recognition by the host, while at the same time updating the name of scab resistance loci (Rvik) and QTL loci (Qvik) to international standards. For the race-specific interactions, the basic premise is that each Rvik-AvrRvik and Qvik-AvrQvik relationship should be represented by a differential host (k), abbreviated to h(k), carrying only the specific Rvik or (major) Qvik resistance allele and an isolate of the pathogen having lost only the complementary allele at the AvrRvik or AvrQvik locus, race (k), with k representing the number of the specific interaction. Races lacking more than one avirulence gene at different loci will be identified as race (k,l,m,...) and apple hosts carrying multiple scab resistance genes as host (k,l,m,...). The proposed system has some continuity with the current system, but should simplify the presentation and interpretation of studies on avirulence alleles in V. inaequalis at the population level. Gene-for-gene relationships reported to date for this pathosystem are reviewed, some inconsistencies clarified, and several new interactions added. The gene-for-gene relationships of European isolates collected in the last decade have been studied in order to establish a new set of reference isolates that represent various V.inaequalis races