genus Vitis, such as Vitis riparia, Vitis rupestris, and Vitis berlandieri. However, many of these were less adapted to the lime-rich soils that were common in France's vineyards, in particular many of those that produced wines of top quality. Many grafted vines in lime-rich vineyards therefore showed signs of iron deficiency, and in France this specific form of chlorosis was termed chlorose calcaire. The problem was largely overcome by the selection of lime-resistant American vines as basis for hybrid vines used for rootstock material. However, since such rootstocks may be less than optimal in other respects, it is necessary for the viticulturalist to balance the need for chlorosis resistance against other viticultural needs. This is illustrated by one of the most common lime-resistant rootstocks, 41 B, which is a hybrid between V. vinifera cultivar Chasselas and V. berlandieri, which generally has a sufficient, but not extremely high, Phylloxera resistance. Treatments Specific nutrient deficiencies (often aggravated by high soil pH) may be corrected by supplemental feedings of iron, in the form of a chelate or sulphate, magnesium or nitrogen compounds in various combinations. See also Forest pathology Phytopathology Virescence References Physiological plant disorders