Iron stress response of three peach rootstock cultivars: Ferric‐iron reduction capacity¹

Received for publication May 5, 1994. This work was completed in June 1989, as part of the peach rootstock screening project of the Texas A&M peach breeding program.

Abstract

Three peach rootstocks were evaluated for their capacity to reduce ferric‐iron (Fe³⁺) after iron‐stress treatment. Neither of the rootstocks with tolerance to iron (Fe) chlorosis [Titan¹ x Nemaguard (Prunus dulcis (all.) D. A. Webb x Prunus persica (Batsch) L.] nor ‘Montclar’ (P. persica) showed consistently higher Fe‐stress induced Fe³⁺ reduction/g root fresh weight (RFW) compared to the less tolerant rootstock Nemaguard [(P. persica)]. However, non‐stressed ‘Titan’ x Nemaguard (TNG) showed higher leaf chlorophyll content than both ‘Montclar’ (MC) and Nemaguard (NG) and higher mean Fe³⁺ reduction by root released reductants than Nemaguard. The reduction rate by root released reductants was approximately 22–34% for NG, 15% for MC, and 29% by TNG. ‘Titan’ x Nemaguard and Montclar maintained better root growth (i.e., had less root necrosis) under Fe‐stress than NG which resulted in greater Fe³⁺ reduction per plant. This indicates that the maintenance of a greater root surface area during Fe‐stress may be important for the sustenance of significant Fe³⁺ reduction capacity under prolonged stress on a per plant basis. Fe‐stressed plants of all three rootstocks showed increased formation of root hairs and slightly enlarged root tips, although these died with prolonged Fe‐deficiency in the nutrient solution (after three weeks). Using the Fe²⁺‐BPDS gel medium procedure, Fe³⁺ reduction sites were localized at approximately 2–10 mm behind the root tips and on the newly formed lateral roots. Although no differences in Fe³⁺ reduction at the root surface were seen among rootstocks, Fe³⁺ reduction in gel medium was more localized and developed earlier in roots of Fe‐stressed plants and those which had nitrogen (N) present in the gel medium as nitrate (NO₃‐) only [versus NO₃‐ + ammonium (NH₄+)].

Notes

Received for publication May 5, 1994. This work was completed in June 1989, as part of the peach rootstock screening project of the Texas A&M peach breeding program.