We report Agrobacterium tumefaciens-mediated transformation of two Prunus salicina varieties, 'Angeleno' and 'Larry Anne', using a modification of the hypocotyl slice technique previously described for P. domestica. Regeneration rates on thidiazuron (TDZ) and indole-3-butyric acid (IBA) supplemented Murashige and Skoog (MS) media reached 11% for 'Angeleno' and 19% for 'Larry Anne' hypocotyl slices. Transformation using Agrobacterium tumefaciens GV3101 harboring a plasmid with the neomycin phosphotransferase II (nptII) and the green fluorescent protein (gfp) genes produced ten independent lines, six from 'Angeleno' and four from 'Larry Anne', representing transformation efficiencies of 0.8 and 0.3%, respectively, relative to the initial number of hypocotyl slices. Plants of six lines were found to produce the transgene encoded mRNAs. DNA blotting demonstrated the presence of transgene sequences in trees from five lines after 18 months of growth in the greenhouse.

A new plant commensal Pseudomonas veronii isolate (strain R4) was identified from a Xiphinema index biocontrol screen. Isolated from grapevine roots from vineyards in central Chile, the strain R4 exhibited a slower yet equivalently effective nematicide activity as the well-characterized P. protegens CHA0. Whole genome sequencing of strain R4 and comparative analysis among the available Pseudomonas spp. genomes allowed for the identification of gene clusters that encode putative extracellular proteases and lipase synthesis and secretion systems, which are proposed to mediate—at least in part—the observed nematicidal activity. In addition, R4 strain presented relevant gene clusters related to metal tolerance, which is typical in P. veronii. Bioinformatics analyses also showed gene clusters associated with plant growth promoting activity, such as indole-3-acetic acid synthesis. In addition, the strain R4 genome presented a metabolic gene clusters associated with phosphate and ammonia biotransformation from soil, which could improve their availability for plants.Electronic supplementary materialThe online version of this article (doi:10.1186/s40793-016-0198-y) contains supplementary material, which is available to authorized users.

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The fungi Botrytis cinerea and Erysiphe necator are responsible for gray mold and powdery mildew diseases, respectively, which are among the most devastating diseases of grapes. Two endochitinase (ech42 and ech33) genes and one N-acetyl-β-D-hexosaminidase (nag70) gene from biocontrol agents related to Trichoderma spp. were used to develop a set of 103 genetically modified (GM) 'Thompson Seedless' lines (568 plants) that were established in open field in 2004 and evaluated for fungal tolerance starting in 2006. Statistical analyses were carried out considering transgene, explant origin, and plant response to both fungi in the field and in detached leaf assays. The results allowed for the selection of the 19 consistently most tolerant lines through two consecutive years (2007-2008 and 2008-2009 seasons). Plants from these lines were grafted onto the rootstock Harmony and established in the field in 2009 for further characterization. Transgene status was shown in most of these lines by Southern blot, real-time PCR, ELISA, and immunostrips; the most tolerant candidates expressed the ech42-nag70 double gene construct and the ech33 gene from a local Hypocrea virens isolate. B. cinerea growth assays in Petri dishes supplemented with berry juices extracted from the most tolerant individuals of the selected population was inhibited. These results demonstrate that improved fungal tolerance can be attributed to transgene expression and support the iterative molecular and physiological phenotyping in order to define selected individuals from a population of GM grapevines.