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Ventimiglia di Sicilia, Italy

Giovannini A.,Italian Agricultural Research Council | Scariot V.,University of Turin | Caser M.,University of Turin | Buttafava A.,University of Pavia | And 6 more authors.
Acta Horticulturae

Breeders are always looking for new and novel cultivars to be competitive in the flower market. Low seed germination rate is still a major problem encountered in traditional rose breeding programs. Mutagenic agents, such as ionizing radiation, may be used to enhance seed vigor and increase the productivity, improving sprouting and emergence of buds that are carried out through seed coating. The effects of ionizing radiation on seed vigor are in most cases genotype-dependent, thus irradiation treatments need to be optimised for each different cultivar. In the present study, gamma rays (0, 50, 100 and 200 Gy) were applied on hybrid tea rose seeds in order to set up a radiation protocol for increasing seed germination. Seeds coming from six different croßes of Rosa hybrida commercial cultivars were used in order to gain information on radio-tolerance and germination ability. Source

Bosco R.,University of Turin | Caser M.,University of Turin | Ghione G.G.,NIRP International | Mansuino A.,NIRP International | And 2 more authors.
Plant Growth Regulation

Concentrations of endogenous abscisic acid (ABA) and indole-3-acetic acid (IAA) in Rosa hybrida seed coat and embryos were determined at 28, 35, 42, and 49 days after pollination (DAP), a period encompassing the early-middle stages of seed development. No studies on rose have ever documented simultaneous change in ABA and IAA during these developmental phases in both seed coat and embryo. Plant growth regulators were extracted and then quantified by using high performance liquid chromatography based on solid phase extraction purification. In both the seed coat and embryo, ABA content decreased from 28 DAP (4.39 and 1.36 pmol mg−1, respectively) and onward. Endogenous IAA in seed coat followed the same trend. In contrast, IAA in embryo began to increase at 28 DAP (2.06 pmol mg−1), peaked at 42 DAP (5.06 pmol mg−1), and then declined dramatically at 49 DAP (1.17 pmol mg−1). In embryo, the IAA/ABA ratio was always >1.0 and showed a tendency to increase from 28 DAP to the maximum significant rate at 42 DAP (9.20). The ABA decrease associated with increased IAA levels in embryo could be a result of crosstalk between these two phytohormones. Such a change in the IAA/ABA ratio may signal the end of endodormancy caused by ABA at the pre-cotyledonary stage and the start of increased embryo cell division during the cotyledonary stage, which also results in increased hip weight. © 2014, Springer Science+Business Media Dordrecht. Source

Pipino L.,Ghent University | Pipino L.,University of Turin | Pipino L.,Belgium Institute for Agricultural and Fisheries Research | Scariot V.,University of Turin | And 4 more authors.
Propagation of Ornamental Plants

Rose breeders need reliable and efficient germination protocols to exploit all viable embryos in their breeding programme. A combined physical restriction of the seed coat and a physiological dormancy are present in the achenes of hybrid tea roses resulting in variable and not uniform seed germination. In this study, different treatment combinations were assessed to overcome the mechanical resistence of the pericarp and enhance germination. Both chemical and microbial seed scarification were carried out. A mild scarification with sodium hypochlorite (NaOCl) before stratification promoted a more uniform germination and enhanced the percentage of germination from 49.2% to 65.9%. Epiphytic bacteria, Emercal TM (a product composed by bacteria and co-metabolites produced by bacterial fermentation), or Remedier ® (a commercial formulation of Trichoderma harzianum and Trichoderma viridae), added to the stratification sand, enhanced percentage of germinated seeds but had no effect on the uniformity of germination. Addition of a compost activator to the stratification sand did not improve seed germination. After stratification, pre-sowing treatments with GA 3 were carried out. Immersion of stratified seeds in 1 g l -1 GA 3 highly enhanced percentage of seed germination (77.6%), mean germination time (26.0 days) and uniformity of germination (2.5%) compared to immersion in water (respectively 64.8%, 32.8 days and 7.9%). Therefore, this study proposes a combination of treatments as a reliable optimisation of seed germination protocols for hybrid tea roses. Source

Pipino L.,University of Turin | Pipino L.,Ghent University | Pipino L.,Belgium Institute for Agricultural and Fisheries Research | van Labeke M.-C.,Ghent University | And 4 more authors.

Fertility of hybrid tea roses is often reduced due to their interspecific origin but also to intensive inbreeding. New genotypes used as pollen donors represent an economic risk for a breeding programme, as their influence on seed production is unknown. In this study 11 cut rose genotypes were selected from a company database as high fertile or low fertile male parents, according to the number of seeds per hybridisation. Pollen morphology and in vitro germination of the selected genotypes were characterised. Pollen was either small (mean diameter <30 μm), shrunken, and irregular (abnormal), or large (mean diameter >30 μm), elliptical and crossed by furrows (normal). High correlations were found between the number of seeds produced per hybridisation and the pollen diameter (r = 0.94) or the percentage of normal pollen (r = 0.96). In order to evaluate the predictive power of the models, we conducted regression analyses and performed a validation experiment on genotypes not present in the database and without background information on fertility. Pollen diameter and percentage of normal pollen were characterised and fitted in the regression models for seed set predictions. Validation with an independent dataset gave a good prediction for 83.3% of the data. This indicates that using either the mean pollen diameter or the percentage of normal pollen resulted in effective fertility prediction. This tool could enhance the genetic variability in crossings between hybrid tea roses, thus creating possibilities for less economically risky exploitation of new tetraploid genotypes as male parents. © 2010 Springer Science+Business Media B.V. Source

Caser M.,University of Turin | Dente F.,Italian Agricultural Research Council | Ghione G.G.,NIRP International | Mansuino A.,NIRP International | And 2 more authors.
Propagation of Ornamental Plants

Hybrid tea rose hips were harvested weekly from 7 to 35 days after pollination (DAP). Thereafter, the immature seeds were extracted and surface disinfected. One half of them were directly plated as immature seeds onto culture medium to induce germination under several different phytohormone concentrations and culture conditions; the other half were opened and the embryos were excised and also plated onto similar culture media and conditions to germinate. Results showed that in vitro germination was possible for both embryos and immature seeds commencing at 21 DAP. The optimum protocol (final germination percentage greater than 40%) used embryos at 28 DAP on a medium MS0 supplemented with 2.5 mg l-1 BAP and 0.5 mg l-1 GA3, which had been incubated for one week at 4°C in dark conditions and subsequently transferred under a 16 h photoperiod at either 23°C or 15°C. The protocols developed in this investigation might help breeders to improve and speed seed germination and to screen a wide morphological variability which would result in shortened selection time. Source

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