Analysis of contrast iron chlorosis tolerance in the pear cv. 'Huangguan' grafted onto pyres betulifolia and quince A grown in calcareous soils

摘要

Quince (Cydonia oblonga Mill.) represents an examplar rootstock in modern training programmes to escalate pear production worldwide because of its dwarfing characteristic and precocity. However, iron deficiency often poses a hard hurdle to overcome for developing quince grafted pears in calcareous and alkaline soils. In North China, we observed that the high-quality pear cultivar Huangguan (Pynus bretschneideri Rehd.) grafted onto quince A (Hardy as interstock, defined as HG-QA) suffered iron deficiency chlorosis in calcareous soils in early spring, even more severe during late spring to early summer. In contrast, Huangguan grafted onto Pyrus betulifolia (Hardy as interstock, defined as HG-PB) did not suffer it. We were inspired to design this field experiment to figure out iron mobilization/uptake in the two rootstocks and the two scion-rootstock combinations. Our results showed that the soil plant analysis development (SPAD) values of quince A (24.7) and HG-QA (13.7) were much lower than that of Pyrus betulifolia (41.6) and HG-PB (36.1). The root length density and surface area density of quince A and HG-QA were more than 2-fold higher than those of Pyrus betulifolia and HG-PB. The rhizosphere pH of quince A and HG-QA was more than 0.20 units lower than that of Pyrus betulifolia and HG-PB respectively, whereas we didn't detect any obvious differences in the root ferric-chelate reductase activity, iron concentrations in leaves and roots, and iron transport ratio. These results strongly suggest that the iron efficiency of HG-PB is attributed to an iron activation mechanism in leaves. The deciphering of the mechanisms that how rootstock influences the iron acquisition system inside the leaf of the scion and changes the efficiency of iron utilization will facilitate making effective solutions for iron deficiency induced chlorosis, popularizing and planting Huangguan grafted onto quince A in pear production.