Difference in physiological response of different pear rootstocks under iron deficiency stress

Objectives The study was aimed to provide theoretical bases for breeding high Fe use efficiency cultivar by comparing the difference in Fe distribution and content of organic acid in pear rootstocks under Fe deficiency.

Methods A hydroponic experiment was carried out with three cultivars, which were HB-Pyrus betulaefolia (HB-Ⅰ), ZZ-Pyrus betulaefolia (ZZ-Ⅱ) and HS-Pyrus ussuriensis (HS) supplied by 1 μmol/L FeNa-EDTA and 40 μmol/L FeNa-EDTA. After 21 days, the characteristic of root architecture and the content of active Fe, total Fe and organic acids in each part of pear rootstocks were determined.

Results Under iron deficiency stress, the active iron and total iron accumulation in the leaves of HB-Ⅰ were 15.71 and 78.82 mg/plant, the distribution ratios of active and total Fe in stems and leaves were 2.80 and 2.94 times of those in ZZ-Ⅱ and 3.29 and 2.05 times of those in HS, respectively. The chlorophyⅡcontents in the first leaf from the top of both ZZ-Ⅱ and HS were all significantly higher than that of HB-I. The content of citric acid was the highest in three kinds of pear rootstocks, followed by malic acid, and they accounted for 74.8% of total organic acid content in the three pear stocks. The malic acid contents in roots and leaves of HS under iron deficiency were 0.96 and 4.80 mg/g, respectively, which were 4.70 and 1.69 times of those under normal iron treatment and were significantly higher than those in both HB-Ⅰ and ZZ-Ⅱ. In the roots and leaves of HB-Ⅰ and ZZ-Ⅱ, the citric acid contents were relatively higher than other organic acids, especially in HB-I, reaching 4.02 and 11.98 mg/g.

Conclusions The absorption and transportation of iron in the three cultivars of pear rootstocks were physiologically different. The root absorption capacity of Pyrus betulaefoliaⅠ was relatively better, and content and accumulation of active iron in root and leaves were relatively higher. As compared with other varieties, Pyrus betulaefoliaⅠ was non-susceptible to iron deficiency. Under iron deficiency stress, the root of Pyrus ussuriensis mainly synthesized malic acid, while the root of Pyrus betulaefolia mainly synthesized citric acid, which suggested one of the mechanisms for their different responses to iron deficiency.