Response to iron‐deficiency stress of pear and quince genotypes¹

Dipartimento di Colture Arboree, Bologna, Publication No. 1128. Study supported by funds of Regione Emilia‐Romagna as part of a programme managed by ERSO of Cesena (Forlì).

Abstract

Roots of iron (Fe)‐efficient dicots react to Fe‐deficiency stress by strongly enhancing the ferric (Fe³⁺)‐reductase system and by lowering the rhizo‐sphere pH. In this study, we tested whether such adaptation mechanisms characterize pear and quince genotypes known to have differential tolerance to calcareous and alkaline soils. Two trials were performed using micropagated plants of three quince rootstocks (BA29, CTS212, and MC), three Pyrus communis rootstocks (OHxF51 and two selections obtained at the Bologna University: A28 and B21) and of two pear cultivars (Abbé Fétel and Bartlett, own‐rooted). In the first trial, plants were grown in a nutrient solution with [Fe(+)] and without [Fe(‐)] Fe for 50 days. Their root Fe‐reducing capacity was determined colorimetrically using ferrozine and FeEDTA, and Fe uptake of Fe(+) plants was estimated. In the second trial, the rhizosphere pH of plants grown in an alkaline soil was measured by a micro‐electrode. With the only exception of pears OHxF51 and A28, whose Fe‐reduction rates were similar in Fe(+) and Fe(‐) plants, the Fe‐deficiency stress resulted in a significant decrease in Fe reduction. Among the Fe(‐) plants, the two pear cultivars, OHxF51 and A28, had a higher Fe‐reducing capacity than the quince rootstocks and the cv. Abb6 F. When plants were pre‐treated with Fe, reduction rate was highest in the P. communis rootstocks, intermediate in the own‐rooted cultivars, and lowest in the quinces. Root Fe‐reducing capacity of Fe(+) plants proved to be linearly and positively correlated with Fe uptake and root proton release. Rhizosphere pH was highest in quince MC, intermediate in the other two quinces and in the cv. Abbe F., and lowest in the pear rootstocks and in the cv. Bartlett. Our results indicate that roots of pear and quinces do not increase their ability to reduce the Fe under Fe‐deficiency stress. The genotypical differential tolerance to Fe chlorosis likely reflects differences in the standard reductase system and in the capacity of lowering the pH at the soil/root interface. The determination of the root Fe‐reducing capacity is a promising screening technique for selecting pear root‐stocks efficient in taking up Fe.

Notes

Dipartimento di Colture Arboree, Bologna, Publication No. 1128. Study supported by funds of Regione Emilia‐Romagna as part of a programme managed by ERSO of Cesena (Forlì).