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Micropropagation in viticulture: twenty years of experience

O. Navacchi, G. Zuccherelli
Vitroplant Italia, via Loreto 170, 47521 Cesena (FC), orianonavacchi@vitroplant.it.

Vitroplant began as a micropropagation laboratory in the early 1980’s to respond to a growing need for hybrid peach-
almond GF677 rootstocks that were particularly suited to excessively dry or soils inducing chlorosis and for replanting. 
This rootstock, selected in France, is relatively simple to propagate in vitro while it is more difficult to carry out multipli-
cation by cuttings. In subsequent years the range of in vitro propagated species grew and, in addition to other peach root-
stocks, self-rooting peach, apricot, kiwi, artichoke and pear rootstocks started being multiplied. Today, micropropagation 
is the most advanced agamic multiplication technique allowing an elevated number of genetically identical plants to be 
obtained in a short time due to an exponential growth rate of the number of individuals with each subculture step. In vitro 
culture offers the advantage of high quality and health safety of the plant material as it not subject to an accumulation of 
pathogens or viruses over the years, as can occur with other agamic in vivo propagation techniques. Moreover, in vitro 
procedures pass on to plants a physiologic equilibrium that is comparable to that of seed-grown individuals, demonstrat-
ing good vigor of the aerial structures and notable rhizogenic exploratory ability in roots. These behaviors can be asso-
ciated with a “rejuvenation” of the plant material. For example, the majority of grapevine cultivars have been, over the 
millennia, vegetatively propagated and for this reason they present important problems from a health standpoint. Toward 
the end of the 1980’s Prof. Carmine Liuni, director of the Viticulture Institute of Turi (Bari), proposed a collaboration 
with Vitroplant for in vitro propagation with the aim of resolving some of the numerous problems found in viticulture 
nurseries. Initially the idea was to use this propagation technique to multiply some known rootstocks and new seedless 
table grape varieties. The results obtained from field tests were very satisfactory. The micropropagated plants were very 
vigorous and demonstrated excellent development of rooting structures, highlighting the potential of this propagation 
technique also in grapevine. This type of development, comparable to seed-grown plants, is not due to genetic mutation 
but rather to phenotypic manifestations that come from the rejuvenation of in vitro-produced plants. Juvenile phases are 
recognizable in some arboreal species thanks to specific morphological, cellular or physiological traits such as a particu-
lar leaf size, shape or phyllotaxis, the presence of thorns or ability to root. Plants do not however undergo genetic varia-
tions as they pass from the juvenile to the adult phase, instead these morpho-physiologic differences are expressions of 
the genotype. Juvenile as well as adult tissues can be present on the same plant at the same time, a phenomenon called 
heteroblasty, and leaves on a single plant can have different forms. Juvenile tissues are generally found in the lower por-
tion of the trunk and branches. To lower the point of transition from juvenile to adult tissues, it is possible to make a cut 
near ground-height, avoiding the risk of juvenile tissues in the shoots intended for production. Micropropagation has 
shown to be an essential technique for the production of healthy material in quantity and rapidly, two aspects that are 
very useful for clonal selection or genetic improvement programs, providing nurseries with sufficient starting material in 
a timely manner. Micropropagated plants, as self-rooted plants not needing rootstock, can be subject to phylloxera attack. 
With careful attention to the selection of soil for mother plant fields and suitable preventative measures, it is possible to 
keep this pathogen under control. In any case, after five or six years micropropagated mother plants have fulfilled their 
purpose: they have provided quickly healthy buds for propagation. Today it is increasingly difficult to keep mother plants 
healthy in open fields and a reduction of their useful period with frequent renewal can be predicted for the future. A new 
frontier for nurseries in coming years may be the use of rootstocks amenable to genic silencing to induce resistance to 
viruses or other pathogens of the varieties onto which they are grafted. Unfortunately considerable difficulty can be ex-
pected with regard to the spread of this technique in Europe where there is deep aversion toward biotechnology, while in 
other emerging, future-competitor grape-growing countries the technique has a better chance of taking hold.

Adv. Hort. Sci., 2013 27(3): 105