Use of biochemical parameters to select grapevine genotypes resistant to iron-chlorosis

Iron-deficiency-induced chlorosis is a widespread nutritional disorder in g rapevine, in particular when alkaline or calcareous soils are concerned. A temporary solution of the problem could be the utilization of Fe-chelates d irectly supplied through foliar spray or as application to the soil. Since Fe-efficiency is genetically determined a possible long term solution might be the development of genotypes resistant to iron-chlorosis. Plants can re spond to Fe-deficiency by inducing biochemical modifications resulting in a n increase in the availability of the soluble forms of Fe in the rhizospher e. Increased medium acidification and Fe3+ reduction, brought about by plas malemma localized H+-ATPase and NADH:Fe3+-reductase activities, respectivel y, were among the most important responses in strategy I plants. The possib ility of using these two activities as determinants of Fe-efficiency in gra pes seems to be realistic as a method of selecting efficient rootstock geno types in a screening program. Eleven new interspecific hybrids were tested for their resistance to Fe-deficiency by measuring their abilities to acidi fy the medium and to reduce Fe3+ For a better evaluation of the results, It vinifera cv Cabernet Sauvignon were employed as references. These activiti es varied widely among the hybrids tested, We can define two groups: the fi rst as efficient in its response to iron-chlorosis and the second as less e fficient in the response to this nutritional disorder.