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Sulle Orme del Castagno - Acta Horticulturae

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170<br />

kuriphilus e il balanino <strong>del</strong>le castagne Curculio elephas;<br />

da patogeni quali Phytophthora cinnamomi,<br />

agente <strong>del</strong> mal <strong>del</strong>l’inchiostro e Cryphonectria parasitica,<br />

agente <strong>del</strong> cancro <strong>del</strong>la corteccia. A ciò sono<br />

da aggiungere le difficoltà da commercializzazione<br />

dovute in parte alla scarsa familiarità con la castagna<br />

come alimento da parte <strong>del</strong>la maggioranza dei consumatori<br />

americani. La maggior parte <strong>del</strong>le castagne<br />

vendute negli Stati Uniti sono importate, soprattutto<br />

Species Distribution in North America<br />

Naturally-occurring:<br />

C. dentata Southern Ontario and Eastern USA<br />

C. ozarkensis Ozark Plateau<br />

C. pumila Southeastern USA<br />

(C. alnifolia, C. ashei, C. floridana,)* Deep South, Gulf Coast and Florida<br />

Introduced:<br />

C. dentata Midwest, California, Oregon<br />

C. crenata Southeastern USA, California<br />

C. sativa California, Oregon , Washington<br />

C. mollissima wi<strong>del</strong>y distributed in eastern North America<br />

C. henryi Rare (only in cultivation)<br />

C. seguinii Rare (only in cultivation)<br />

_____________________________________________________________________________<br />

*See: Godfrey (1988), Johnson (1988), Nixon (1997), and Ward (2000).<br />

dall’Italia e dalla Cina. Attualmente nel nordamerica<br />

la ricerca inerente al castagno è concentrata nella<br />

ricostituzione e restauro ecologico di C. dentata<br />

(Fig. 3) alla sua posizione di componente <strong>del</strong>l’ecosistema<br />

<strong>del</strong>la foresta decidua <strong>del</strong>l’Appalachia. La<br />

reintroduzione <strong>del</strong> castagno americano si basa su un<br />

autentico approccio multi-disciplinare che coinvolge<br />

ecologia, biologia, sociologia, genetica e biotecnologie.<br />

La reintroduzione <strong>del</strong> castagno americano<br />

richiede uno sforzo multidisciplinare che coinvolge<br />

il servizio forestale degli Stati Uniti, università<br />

statali e private, varie organizzazioni e volontari entusiasti.<br />

Poco dopo la scoperta <strong>del</strong> cancro <strong>del</strong>la<br />

corteccia, ricercatori <strong>del</strong>l’USDA (United States Department<br />

of Agriculture) introdussero da Cina e Giappone<br />

negli Stati Uniti specie di castagno resistenti<br />

al cancro nel tentativo di sostituire il castagno americano.<br />

La Fondazione per il <strong>Castagno</strong> Americano<br />

(TACF) è coinvolta in tutti gli aspetti di questa<br />

colossale impresa per il ripristino di C. dentata, attraverso<br />

un proprio programma di miglioramento<br />

genetico e altri programmi condotti da organizzazioni<br />

affiliate nei diversi stati, oltre che attraverso<br />

finanziamenti elargiti a ricercatori e collaboratori, in<br />

tutti gli Stati Uniti. Attraverso il miglioramento genetico,<br />

TACF ha trasferito i geni di resistenza al cancro<br />

<strong>del</strong>la corteccia da C. mollissima a C. dentata<br />

facendo il possibile per conservare la variabilità genetica<br />

di quest’ultimo. La ricerca ha fatto sforzi<br />

notevoli per il restauro <strong>del</strong> castagno americano, sopratutto<br />

negli ultimi 25 anni (3,7) , e grandi passi avanti<br />

sono stati fatti verso l’ottenimento di un ibrido che<br />

unisca la forma ad alto fusto <strong>del</strong>la specie americana<br />

alla resistenza al cancro <strong>del</strong> castagno cinese (8,9,10) .<br />

Species and distribution<br />

The loss of C. dentata to the chestnut blight pandemic<br />

in the early 20 th century effectively ended the<br />

experience of American chestnut for most Americans,<br />

and chestnut culture in North America is currently<br />

based almost entirely on introduced species<br />

and their hybrids (Table 1). There are currently recognized<br />

three species of Castanea naturally occurring<br />

in North America: C. dentata, the American<br />

chestnut, and C. pumila and C. ozarkensis, the<br />

chinkapins. Only C. dentata was ever of any economic<br />

importance, as a valuable source of timber<br />

and for its <strong>del</strong>icious and nutritious nuts. C. dentata<br />

can grow to be a large tree, often attaining 35 m,<br />

while C. pumila and C. ozarkensis are highly variable<br />

but usually shrubby, small trees rarely more<br />

than 10 m tall. All three species had and continue to<br />

have important ecological functions in the forests of<br />

the eastern United States. Current distributions may<br />

be the result of repeated migrations rather than simple<br />

range reductions C. dentata (Fig. 3) had the<br />

largest historical range covering essentially all of the<br />

upland deciduous forests of the eastern US. There is<br />

considerable controversy surrounding the taxonomy,<br />

morphology, distribution, and phylogeography of C.<br />

pumila and C. ozarkensis (2) . DNA sequence comparisons<br />

reveal a complex phylogeny. C. pumila and<br />

its varieties occur only in the Southeast, and range<br />

into Florida and along the Gulf Coast where populations<br />

of very low-growing, fire-adapted, stoloniferous<br />

types occur.<br />

Economical and technical data<br />

Commercial chestnut orchards in the United<br />

States make up a very small, but thriving industry, in<br />

two very different regions of the United States: the<br />

West Coast, and the East. Major threats to successful<br />

chestnut orcharding include pests such as Asian ambrosia<br />

beetles, oriental chestnut gall wasp, and chestnut<br />

weevils, diseases such as those caused by<br />

Phytophthora cinnamomi,andCryphonectria parasitica,<br />

and marketing challenges due, in part, to the<br />

relative unfamiliarity of chestnuts as a food to the<br />

vast majority of American consumers. Most of the<br />

chestnuts consumed in the United States are imported,<br />

primarily from Italy and China. The major<br />

focus of chestnut research in North America today is<br />

the restoration of C. dentata to its former position as<br />

a component of the Appalachian hardwood forest<br />

ecosystem. The return of the American chestnut is<br />

based on a truly multi-disciplinary plan of action involving<br />

ecology, biology, sociology, genetics and

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