Responses of two asian pear rootstocks (Pyrus spp.) to Fe-deficiency chlorosis induced by addition of bicarbonate to nutrient solution

To evaluate the tolerance of two Asian pear rootstock species, Pyrus xerophila Yue and Pyrus betulaefolia Bunge, to lime-induced Fe chlorosis, seedlings were grown in a nutrient solution with or without bicarbonate. After 20 days in the bicarbonate solution, P. betulaefolia seedlings became chlorotic, a symptom of Fedeficiency, whereas those of P. xerophila did not. Leaves of the P. xerophila had higher chlorophyll (SPAD value) while the stem amassed more Fe than did those of P. betulaefolia, which indicates that the former may be more tolerant to lime-induced Fe chlorosis than may be the latter. Furthermore, higher Fe(3+)-chelate reductase activity in root tips was observed in two pear rootstocks grown in the bicarbonate solution; seedling of P. xerophila had twice the activity than had those of P. betulaefolia seedlings. Hence, we propos that Fe(3+)-chelate reductase activity in roots tips may be a useful physiological index to select rootstock genotypes that are tolerant to Fe-deficiency chlorosis.