Susceptibility to Chlorosis and Its Relationship to Leaf Iron Contents in some Genotypes of Quince (Cydonia oblonga Mill.)

One of the difficulties of quince cultivation and growing in Iran is calcareous soils which cause leaf chlorosis. This phenomenon appears as leaf yellowish and causes loss of the leaf efficiency and yield of tree. The current research was conducted to evaluate the variation of leaf chlorophyll content and its relationship to the iron contents in the leaves of quince genotypes to select more tolerant ones. Thirty genotypes from Isfahan, Khorasan Razavi and Guilan provinces were evaluated for chlorophyll contents in the leaves of the upper and lower parts of the shoots. The results showed the range of 3.8 to 8.9 mgg-1 of fresh weight for total chlorophyll in the genotypes. The highest quantity of chlorophylls was in July, followed by a reduction in the chlorophyll contents of the majority of genotypes, but the rate of increase was higher for chl b, that caused diminution of chl a/b ratio from 2 and higher to about 1.1 in the mid-summer. The highest level of tolerance to the leaf chlorosis was observed in two genotypes from Khorasan Razavi, encoded as M3 and M4, while genotype KM1 from Isfahan was extremely susceptible. Evaluation of iron contents and chlorosis of the leaves of quince genotypes did not show significant correlation between these traits, not only for the chlorophyll contents of different months, but also for the mean chlorophyll contents of entire growth season.