Effect of cryopreservation on the sanitary state of a cv Prunus rootstock experimentally contaminated with Plum Pox Potyvirus

Abstract

An in vitro grown interspecific Prunus rootstock, Fereley-Jaspi (R), which had been infected by chip budding with the Plum Pox Potyvirus Marcus strain, was used as experimental material. After excision from Fereley plantlets which had been subcultured 7, 14, 30 days, shoot tips were sorted by size (from 0.3 to 2 mm). Control shoot tips were grown directly on meristem culture medium. Experimental shoot tips were cultured 24 h at 4°C on a preculture medium enriched with dimethylsulfoxide and proline, then treated with modified PVS2 cryoprotective solution and cooled at 1°C/min to −40°C before immersion in liquid nitrogen. When plantlets, from both, control and cryopreserved shoot tips were 4 month old, they were tested by the immunocapture Polymerase Chain Reaction method (IC-PCR) for Plum Pox virus detection. An average of 50 and 20%, respectively for frozen and control shoot tips were virus free. The impact of cryopreservation on producing virus-free plantlets was also studied in relation to shoot tip size and to the duration of subculture of the plantlets before excision of the shoot tips. Both of these parameters influenced the percentage of virus-free plantlets obtained from control shoot tips, but not that obtained from cryopreserved ones.