The first efficient cryopreservation procedure for in vitro-grown shoot tips of raspberry (Rubus idaeus L.) has been developed based on encapsulation-vitrification (EnVi) and encapsulation-dehydration (EnDe). EnVi resulted in higher survival (85%) and regrowth (75%) of cryopreserved shoot tips than EnDe (65 and 50%, respectively). In both cryogenic procedures, shoots regenerated from cryopreserved shoot tips without intermediary callus formation. Histological studies showed that a much larger number of meristematic cells survived following EnVi than EnDe. The EnVi procedure was applied to seven raspberry genotypes with an average survival and regrowth of 71 and 68%, respectively. Regenerated plants showed normal morphology. Results here indicate EnVi as a simple and efficient method for long-term preservation of R. idaeus germplasm.
Expansion and intensification of global trade in horticultural plants has increased the risk of spread of new alien pathogen species in the European Union (EU). Alien species of pathogenic viruses and viroids in horticultural plants have been introduced into Finland in infected plant material (plants, seedlings, cuttings, tubers, seeds). By 1997, about 30 virus species of horticultural plants had been detected in Finland. We aimed at compiling emerging new virus and viroid records during 1997-2010. Eight new viruses belonging to tospo-, potex-, poty-, tymo-, ilar-and allexiviruses were detected in horticultural plants: four occurred in greenhouse crops, two in vegetables and two in garden ornamentals outdoors. Five new findings of viroids were made in ornamental and vegetable greenhouse crops during 2008-2009. More rapid and accurate diagnostic methods have contributed to identifying new alien pathogens. Global trade seems to be the main reason for the introduction of the newest virus and viroid pathogens into Finland.
The aim of plant gene banks is to preserve genetic resources selected based on their phenotypic, agronomic, historical or other cultural values for future utilization. In the present study the modified PVS2 droplet vitrification technique was tested and optimized for cryopreservation of a large diversity of blackcurrant (R. nigrum L.) accessions propagated in vitro and selected into a national gene bank core collection. Out of four accessions tested to optimize the method, three recovered and regenerated by 89–97% on average, but one recalcitrant in vitro line only by 25%. The tested post-cryopreservation recovery media with different macronutrient and growth regulator levels showed no generalized effect on regenerated shoots, but the effect of recovery media was different between cultivars. When the whole regeneration chain from cryopreservation via micropropagation to greenhouse conditions was tested, shoots at least 1 cm in length were found necessary for successful transfer ex vitro. The long-term cryopreservation of 22 blackcurrant accessions was finally conducted, with practices slightly modified from the tested protocol. The estimated recovery of shoot tips after 9 weeks in vitro was 17–94% with at least 75% recovery in seven accessions and at least 40% recovery in 19 out of 22 accessions. Only one accession had no cryopreservation success. The results demonstrated that the modified droplet vitrification technique is appropriate for a large diversity of blackcurrant accessions. However, cultivar-related differences and recovery procedures are to be considered for success in regeneration and ex vitro adaptation.
Pathogen-free stocks of vegetatively propagated plants are crucial in certified plant production. They require regular monitoring of the plant germplasm for pathogens, especially of the stocks maintained in the field. Here we tested pre-basic mother plants of Fragaria , Rubus and Ribes spp., and conserved accessions of the plant genetic resources of Rubus spp. maintained at research stations in Finland, for the presence of viruses using small interfering RNA (siRNA) -based diagnostics (VirusDetect). The advance of the method is that unrelated viruses can be detected simultaneously without resumptions of the viruses present. While no virus was detected in pre-basic mother plants of Fragaria and Ribes species, rubus yellow net virus (RYNV) was detected in pre-basic mother plants of Rubus . Raspberry bushy dwarf virus (RBDV), black raspberry necrosis virus (BRNV), raspberry vein chlorosis virus (RVCV) and RYNV were detected in the Rubus genetic resource collection. The L polymerase encoding sequence characterized from seven RVCV isolates showed considerable genetic variation. The data provide the first molecular biological evidence for the presence of RYNV in Finland. RYNV was not revealed in virus indexing by indicator plants, which suggests that it may be endogenously present in some raspberry cultivars. In addition, a putative new RYNV-like badnavirus was detected in Rubus spp. Blackcurrant reversion virus (BRV) and gooseberry vein banding associated virus (GVBaV) were detected in symptomatic Ribes plants grown in the field. Results were consistent with those obtained using PCR or reverse transcription PCR and suggest that the current virus indexing methods of pre-basic mother plants work as expected. Furthermore, many new viruses were identified in the collections of plant genetic resources not previously tested for viruses. In the future, siRNA-based diagnostics could be a useful supplement for the currently used virus detection methods in certified plant production and thus rationalize and simplify the current testing system.
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