Evaluation ofsalt tolerance ofin vitro-grown grapevine rootstock varieties

S u m m a r y : The response of 11 grapevine rootstock varieties to increasing salt concentrations (0, 50, 85, 120, 155 mMNaCI) was studied under in vitro and growth chamber conditions . The effect of salinity on the mortality of explants was compared with that of plantlets grown under growth chamber conditions and with data in literature on rootstock resistance under field conditions . In addition, in vitro stem elongation, bud number, and rooting ability were related to salinity. The rootstock varieties can be divided into sensitive (41 B, R.Lot, 110 R, 140 R and 161-49), moderately tolerant (13 .5 and Ramsey) and tolerant (196-17, CH-1, CH-2 and Superior) . Measurements ofthe water and nutrient contents ofplantlets indicate that increasing salt concentrations decreased the hydration ofaerial parts and roots of all plants ; however, the decrease of hydration was smaller in salt tolerant varieties . Increasing salt concentrations significantly reduced the K content and, to a smaller extent, the P and Ca contents . With and without salt treatments the levels of K and P were lower in sensitive plants . Na and Cl accumulated to a higher extent in tolerant plants . The tolerance to NaCl of in vitro-grown rootstocks seems to be due to their capacity to accumulate salt, to increase K concentration in the tissue and to maintain a high water content . Our results indicate that salt tolerance of grapevine varieties may be tested under growth chamber conditions and using in vitro explants.