Management of genetic resources in the nursery system of wild cherry (Prunus aviumL.)

Abstract

Management of genetic resources in the nursery system of wild cherry (Prunus avium L.).Knowledge of genetic and adaptive traits of reproductive materials used in the nursery system of wild cherry, could be an useful instrument to improve ecological and economic sustainability of plantation ecosystems. This work reports results from a research which the objectives were: 1) to study the genetic variation of a Prunus avium L. population, used for seed harvesting, through its multi-locus genotypes detected by starch gel electrophoresis; 2) to analyze the level of genetic variation within and among different steps in a commercial nursery system (basic population and sub-populations, seedlings aged S 1 T 1 and S 1 T 2 , plantation). Results showed low genetic variation levels of the basic population, similar to a reference system of other 12 wild cherry Italian populations and to other French and Caucasian materials. The genetic distances among Monte Baldo and some closer Lombardy provenances (Area Garda, Bosco Fontana, Valtellina) were smaller than the Venice Region populations (Monti Lessini and Asiago). Number of alleles and percentage of polymorphic loci within the complex of Monte Baldo provenance and multiplication materials were similar, whilst a variable value of Fis was noted. Indeed, along with the nursery system until the plantation, heterozygosis initially (S 1 T 1 ) increased, then decreased proceeding to the plantation. This fluctuation of F IS values could be determined by seed lots characterized initially by higher levels of variation, due to self-incompatibility. In the following steps, a possible selection pressure can affect randomly the genotypic structure of wild cherry by increasing the homozygosity. There is not among population a well defined geographic characterization, as suggested by genetic distances, therefore homogeneous seed harvest could be established an area larger than geographic and administrative borders. On this way we could have reproductive material with a wide genetic base and environmental adaptability. To increase variability in the progenies, populations characterised by wider cross pollination rates should be selected, harvest seed by all plants of population, reduce selection on seedlings during nursery growth.Keywords: P. avium, Nursery system, Genetic variation, Isozymes. Introduzione L'adattabilità e la sostenibilità di un ecosistema naturale o artificiale è legato al livello di diversità in esso presente (Namkoong 1998, Tessier du Cros et al. 2000. Questa assume grande importanza nelle specie forestali poiché, a causa della lunghezza del loro ciclo biologico, sono maggiormente esposte a rischi determinati dall'ambiente circostante. Un'ampia variabilità genetica conferisce alle popolazioni naturali ed alle piantagioni migliore plasticità evolutiva e di adattamento ai possibili cambiamenti ambientali, sia biotici che abiotici.Il mantenimento di sufficienti livelli di variabilità è, quindi, uno degli elementi principali che deve considerare chi opera in vivaisti...