Tolerance of Pyrus spp. and Cydonia oblonga as pear rootstocks to iron chlorosis determined by in vitro growth, antioxidant and molecular responses

Determination of Fe-efficient rootstock genotypes is important for the success of pear cultivation in calcareous soils. Otherwise, the use of iron-containing fertilizers against Fe-chlorosis for a long time may cause significant environmental hazards. In the present study, the morphological, antioxidant and molecular responses of Pyrus elaeagrifolia (AH-0 and AH-1 wild pear clones), P. communis (OHxF 333) and Cydonia oblonga (QA) as pear rootstocks to iron deficiency were determined in vitro micro shoots. Iron deficiency was created by reducing the amount of ferric-sodium EDTA added as 0.1 mM at full strength in modified Murashige and Skoog's basal medium to 0.03 mM or 0.0 mM. After six weeks in cultures, shoot proliferation percentage, shoot number per explant, shoot length, dry and fresh weight, proline content, H2O2, total chlorophyll and Fe content, CAT (EC 1.11.1.6), SOD (EC 1.15.1.1) and APX (EC 1.11.1.11) activities were determined. The expression of the dehydrin gene DQ660905 originated from Malus domestica associated with stress response was evaluated in Fe-deficient micro shoots at 1, 2, 4, 8 days after stress. According to the findings, the percentage of decrease in the number of shoots and length of wild pear clones were lower than those of OHxF 333 and QA under Fe deficiency. Fresh and dry weights of all genotypes were increased in media containing ferric-sodium EDTA. Under Fe deficiency conditions, total chlorophyll of micro shoots was reduced in all genotypes. However, the decrease was not statistically significant only in the AH-0 wild pear clone. Also, prolin remained statistically the same in this clone with the decrease of ferric-sodium EDTA level in the medium, but increased significantly in other genotypes. APX and SOD activities of AH-1 clone were higher than other genotypes in deficient conditions. Differential expression of the dehydrin gene DQ660905 revealed that the highest increase was determined in QA, AH-1 at day 1, and in AH-0 at day 4. The overall expression of OHxF 333 was lower than the other genotypes. In conclusion, according to the findings of the study, tolerance of wild pear clones to Fe deficiency was higher than OHxF 333 and QA rootstocks.