Paperwhite narcissus of the Tazetta group leads flower bulb production in Israel, with more than 20 million bulbs exported annually for dry sales and flower production. The recent release by ARO, The Volcani Center of the new cultivars 'Ariel', 'Inbal' and 'Nir', suitable for pot-plant production necessitate the development of methods for flowering manipulations. Under natural conditions in Israel, paperwhites flower in December-January. In order to advance flowering to October-November, three forcing strategies were applied to 'Ariel', 'Inbal' and the well-known cultivar 'Ziva'. Following the determination of the stage of flower development on 1 July 2007, bulbs were kept in different storage regimes: (1) open shed, temperatures 18-22/25-30 degrees C (night/day); (2) constant 25 degrees C; (3) 25 degrees C, following by 2 weeks at 13 degrees C; (4) 25 degrees C, following by 2 weeks at 9 degrees C. Storage at 25 degrees C accelerated intrabulb flower differentiation and shortened forcing time by 2 weeks in 'Ziva' and 'Inbal' and by 4 weeks in 'Ariel', in comparison with the open shed control. Storage at 9 and 13 degrees C for 2 weeks prior to planting caused stalk elongation inside of the bulb. Bulbs were planted on 1 September in 15 cm pots, 3 bulbs/pot, and grown in the phytotron at 20/12 degrees C (day/night) and 10 hours of natural sun light. In all cultivars, storage at 25 degrees C followed by a short period at lower temperatures of 9 or 13 degrees C resulted in the anthesis on 7-10 October, after 37-40 days of growth. Thus the time to anthesis was reduced by 16-18 days in comparison to the control. Storage at 25 degrees C advanced anthesis by 9-10 days. In 'Ariel' and 'Inbal' lower storage temperatures significantly increased the number and diameter of individual flowers, while the opposite result was obtained for 'Ziva'. Storage at 25 degrees C significantly increased the number of flower stalks per bulb in 'Inbal', but in 'Ziva' the increased number of flower stalks was observed after storage in the open shed. We conclude that the physiological requirements for 'Ariel' and 'Inbal' are different from those of 'Ziva', and that a precise pre-planting protocol is needed for each cultivar.

Bacterial soft rot is one of the most destructive diseases affecting Ornithogalum, and affects many other bulbous crops, ornamental plants and vegetable crops, as well. This disease is caused by Perctobacterium carotovorum (Erwinia carotovora), which penetrates through wounds or stomatal openings, spreads through the apoplast secreting cell-wall degrading enzymes and, eventually, macerates the entire plant and spreads to neighboring plants. There is no known resistance or effective control measure for use against this disease, making utilization of transformation technologies the favored choice for the introduction of disease resistance into this crop. Tachyplesin, a small antimicrobial peptide isolated from hemocytes of the Japanese horseshoe crab, has been reported to inhibit the growth of both Gram-negative and P P Gram-positive bacteria. Liquid-grown cell clusters of O. dubium were bombarded with gold particles coated with a plasmid carrying the nptII gene, conferring kanamycin resistance, a GUS reporter gene, and the Tachyplesin 1 (TPN1) target gene under the control of either the polyubiquitin (UBQ3) or strawberry vein-banding virus Delta SVB) promoter. Following prolonged selection in a liquid medium supplemented with 80 mg/L kanamycin in darkness, the cultures were transferred to regeneration medium in the light, where hundreds of transgenic plantlets developed. The presence of the target gene was confirmed in all of the transgenic plants tested. Upon infection with a highly virulent bacterial isolate from calla lily (Zantedeschia aethiopica), the control plantlets were completely macerated within a week; whereas the transgenic plants showed varying levels of resistance. Half of the transgenic plantlets remained vital and flourished for months following the Erwinia challenge, despite the continued presence of the plant pathogen on and around the plants.

Non-specific plant defense activators and multiple pathways for their transduction may induce resistance in plants against unrelated pathogens. This approach may reduce dependence on chemical pesticides and enhance utilization of relatively susceptible crops that maintain high marketing value. Zantedeschia is a growing crop in the ornamental bulb industry worldwide. The biggest problem in its development and production is the bacterial pathogen Pectobacterium carotovorum, the causal agent of soft-rot disease. Two plant defense activators, Bion, acting through the salicylic acid pathway, and methyl jasmonate, involving the jasmonate-dependent signaling pathway, differed in both their capacity to induce accumulation of polyphenols, and resistance against the pathogen. Methyl jasmonate elicitation brought about higher accumulation of free phenolics relative to Bion, only following challenge with P. carotovorum, suggesting that priming of bioactive polyphenols plays a role in calla lily defense against this pathogen. Results demonstrate enhanced biological activity against the necrotrophic P. carotovorum only in the methyl jasmonate induced plants. To further characterize the nature of induced compounds, two major compounds were collected and identified as c-glycosyl-flavonoids, swertisin and isovitexin by mass and NMR spectroscopies.

Pectobacterium carotovorum subsp. carotovorum (Pcc) is a major threat to some monocotyledonous ornamentals production and development. An example of such susceptible crop is the colorful Zantedeschia also known as calla lily. The bacterial pathogen may destroy a whole crop in just a few days. Nevertheless, the association between Pcc isolates and monocots including calla lilies was hardly studied. We have characterized the virulence of several Pcc isolates from different plant sources towards the ornamental monocot plant Zantedeschia aethiopica (calla lily) and a common dicot plant Brassica oleracea (cabbage). In addition genetic analyses were used to characterize Pcc isolates from diverse geographical locations and from plants belonging to four unrelated orders of ornamental monocots and five orders of dicots. Isolates originating from monocots exhibited higher virulence towards calla lily than dicot isolates. In addition, Pcc isolates were differentiated by their AFLP clustering. We suggest that Pcc isolates from monocots display genetic specialization towards the monocot host calla lily independently of their geographical or plant source.

The potential of three externally applied chemical plant activators, Bion, BABA and methyl jasmonate, known to act only through the plant defence system and not on the pathogen directly, to induce resistance against wild‐type Pectobacterium carotovorum was examined in white‐flowered calla lily (Zantedeschia aethiopica). Following a 24‐h induction period, plants were challenge‐inoculated with P. carotovorum, originally isolated from calla lily or potato plants, previously transformed using a gfp broad‐host‐range promoter‐probe vector. After another 24 h, Bion treatment (10 µg mL−1, as a drench) reduced disease symptoms more than sixfold and bacterial proliferation by four orders of magnitude. BABA treatment (5–10 µg mL−1, also as a drench) reduced the rate of infection by 75–85%. However, the protection afforded by both inducers did not persist. Also, at higher concentrations both displayed a phytotoxic effect. By contrast, methyl jasmonate (10 mm, applied as a leaf spray) completely inhibited P. carotovorum development in calla lily leaves and afforded a long‐lasting effect. It is suggested that the defence response of calla lily against P. carotovorum involves the SA‐signalling pathway in the short term, but the jasmonate/ethylene‐signalling pathway is required for durable protection.

Ornithogalum mosaic virus (OrMV) causes flower deformation and deterioration of planting stocks in species and hybrids of Ornithogalum and Lachenalia. No resistance to viral infection by OrMV is known, making utilization of transformation technologies the natural choice for the introduction of virus resistance. Transformation with viral coat protein (CP) and replicase genes has been shown to confer resistance to viral infection in many plant species. Liquid-grown cell clusters of O. dubium were bombarded with gold particles coated with a plasmid carrying nptII gene, conferring kanamycin resistance, GUS reporter gene, and either CP gene or the viral replicase (N1b) target genes under the control of either polyubiquitin (UBQ3) or the strawberry vein-banding virus deleted (Delta SVB) promoters. Following prolonged selection in a liquid medium supplemented with 80 mg/1 kanamycin in darkness, the cultures were transferred to regeneration medium in the light, where hundreds of putative transgenic plantlets developed. Most of the regenerated plants were GUS-positive. PCR analysis indicated the presence of GUS reporter gene and nptII selectable gene, and either the CP or replicase transgenes. Transgenic plants are being propagated vegetatively before being challenged with virus infection to confirm their state of resistance.

Genetic transformation mediated by bombardment with microscopic metal particles carrying target genes is the preferred method for the introduction of foreign genes into monocotyledonous plants. The fact that most flower bulbs are monocotyle-donous and that almost all commercial cultivars are propagated vegetatively makes them good candidates for molecular breeding through microprojectile bombard-ment. We report here on a development of a reliable method for an efficient genetic transformation of both Lilium longiflorum and Ornithogalum dubium using a particle inflow gun to deliver gene constructs into the target plant tissue, followed by a prolonged selection in the dark in liquid medium supplemented with kanamycin. The system was first optimized for Lilium longiflorum 'Snow Queen'. Based on the level of transient GUS expression, liquid-grown cell clumps are more competent than leaves. Large cell clusters (2-10 mm) maintain their organogenic potential while smaller clusters (<2 mm) cease to grow and die. The liquid-grown tissue cultures have a level of competence for transformation about 50-70 times greater than that of solid-grown callus cultures, and compact cell clusters are more competent than loose clusters. The cells were bombarded with a pCAMBIA2301 vector, carrying nptII gene conferring kanamycin resistance and GUS reporter gene. Following selection for 4-6 months in a liquid medium supplemented with 80 mg l(-1) kanamycin in the dark, the cell clusters were transferred to a regeneration medium in the light where hundreds of transgenic plantlets developed. The plants retained their stable transgenic state when grown in the greenhouse for two seasons. The transformation of O. dubium was similar in principle to that of L. longiflorum with three major differences: lily liquid-grown cultures grew more rapidly and had a higher potential for somatic embryo development. Ornithogalum cultures under selection took longer to develop into semi-organized cell clumps of sufficient size to allow continued shoot regeneration, were mostly organogenic, and the regenerated plantlets had higher rate of vitrification.

Hippeastrum bulb growing in Israel has expanded rapidly in recent years. The growth in terms of the numbers of bulbs produced and the overall area cultivated demands optimization of the propagation method and a shortening the growing period. Various bulb cutting techniques, incubation, and growing methods were studied for the purpose of producing propagules in one growing season, that are capable of developing into marketable bulbs after only one additional growing season.'Red Lion' bulbs were cut into 'chips' (12 segments/bulb) or 'half-chips' (24/bulb) and planted immediately in a greenhouse which was soil heated to 20 degrees C. The results of 11 months' growth indicate the superiority of the 'half-chip' method in which 28.5 bulbils developed per cut bulb compared with 20.4 bulbils obtained by the 'chip' method. Approximately 80% of the bulbs produced by both techniques were of size 12+ (cm in circumference). "Outer" half-chips gave higher yields than the "inner" halves (16.2 and 12.3 bulbils/bulb respectively), incubation of 'twin-scales', 'chips' and 'half-chips' in vermiculite (4.5 months at 23 degrees C) followed by spring planting in a screen-house, was compared with direct planting in the greenhouse. Ten months after bulb cutting, direct planting and pre-incubation yielded averages of 40.3 and 30.4 bulbils/bulb, respectively. Direct planting yielded larger bulbs then the incubation method. The percentage of bulbs larger than size 12 was in direct planting 17.5, 46.5 and 54 for 'twin-scales', 'half-chips' and 'chips' respectively, and after pre-incubation 0, 1.0 and 57%, respectively.The results demonstrate an advantage in the use of the 'half-chip' technique followed by direct planting.

The production of Hippeastrum bulbs in Israel has undergone a significant change in recent years. The shift from open fields into soil-heated greenhouses has resulted in the production of physiologically different bulbs. In addition, there was an increase in production costs that necessitated an optimization of the growing method.The purpose of the present study was to enable the production of marketable bulbs, that are suitable for Christmas forcing, within two growing seasons, after chipping of the mother bulb.'Chips' and 'half-chips' of the cv. 'Red Lion' were planted in a greenhouse which was soil-heated to 20 degrees C. Two growing methods were used: 1) planting at "final density" (24 segments/m(2)) and leaving them in the ground for two seasons; and 2) planting at "double density" (48 segments/m(2)) for 11 months growth, and then lifting, grading and re-planting for an additional season. The bulbs were harvested after 21 months from the day of chipping, and the number and stage of development of flowers buds inside the bulbs were recorded. Bulbs that flowered during the growing season were separated from those that did not flower. Eighty percent of the bulbs planted to "final density" flowered in the second season of growth, whereas only 10% of the bulbs planted at "double density" flowered.'Half-chips' yielded a higher percentage of marketable size bulbs (size 22+) than the 'chips' (88 and 71%, respectively). In 22-30 sized bulbs 1.5-1.8 developing inflorescences larger than 20 mm were found at harvest. In transplanted bulbs, the 12/14-sized bulbs yielded 80% and 16/18-sized bulbs yielded 98% marketable bulbs. Bulbs that flowered before harvest had fewer well developed inflorescences (larger than 20 mm) than those that had not flowered.Representative samples of harvested bulbs were stored at 9 degrees C for 2 months before being forced in the greenhouse. All the bulbs flowered after 38-42 days. The good quality flowering confirmed the predictions based on the bulb sectioning at harvest.