Cytogenetical test to predict the vigour potential in brassica seeds under long-term storage.

Preservation of intraspecific diversity in seed banks is a common strategy to frontier the loss of biodi-versity, however long-term storage inevitably results in the loss of a certain percentage of seeds, there-fore causing the genetic erosion of a seed collection. For this reason seed quality monitoring is of out-standing importance to ensure that the regenerated genetic material is representative of the endemic nat-ural diversity once reintroduced in the environment, as well as to preserve the genetic biodiversity ofspecies economically relevant for modern agriculture. Ageing amplification tests, in which seeds under-go osmotic stresses, enable to detect little differences in the vigour of seeds with high germination per-centage (%G) thereby allowing to predict precociously damages induced by long-term storage.In the present research the quality ofBrassica villosasubsp.drepanensisseeds stored in a genebank (at -20°C for sixteen years) was compared to seeds at harvest (control) by combining %G and mean germina-tion time (MGT) measurements, ageing amplification tests and cytogenetic changes in primary roots.Comparison of %G and MGT between control and stored seeds showed no significant differences.Conversely ageing amplification tests where a saline shock (NaCl -0.9 MPa) was given for six hoursto control seeds or after storage, evidenced no significant influence on %G of control seeds, but sig-nificantly reduced the % G of stored seeds. The treatment with 1.4 MPa osmotic potential significant-ly reduced %G of control and stored seeds (50 and 4% respectively).Cytogenetic analysis clearly showed significant reductions of the mitotic index, the appearance of c– metaphases, chromosomes laggings and bridges in stored seeds in respect to control seeds germinat-ed in water. While the treatment with -0.9 MPa osmotic potential had no significant effects in bothgroups, the treatment with -1.4 MPa osmotic potential had inhibitory effects in root apices of controlseeds and completely prevented cell division in stored ones.The results presented in this study indicate that despite a comparable germinative response of seeds,long-term storage induces cytogenetical damages and increase susceptibility to salt stress, thereforelowering the seed quality.We suggest the use of the ageing amplification test and cytogenetical parameters as more sensi-tive, reliable and inexpensive methods compared to germination percentage tests, allowing an earlyprediction of genetic erosion events in germplasm banks and representing a valuable alternativetool for seed producers