The significance of organic‐anion exudation for the aluminum resistance of primary triticale derived from wheat and rye parents differing in aluminum resistance

Abstract

Eight primary octoploid triticale genotypes (xTriticosecale Wittmack) derived from four wheat cultivars (Triticum aestivum L.) and two rye inbred lines (Secale cereale L.) differing in aluminum (Al) resistance were investigated with respect to their response to Al supply. Aluminum‐induced inhibition of root elongation (48 h, 25 µM Al supply), callose formation, and the accumulation of Al in root tips (4 h, 25 µM Al supply) were used as parameters to assess Al resistance. Using these parameters, the existing information on Al resistance of the wheat and rye cultivars was generally confirmed. The triticale cultivars showed a wide range of Al resistance amongst the Al‐sensitive wheat and the Al‐resistant rye cultivars. The rye parents and the Al‐resistant wheat parent Carazinho were characterized by Al‐induced exudation particularly of citrate but also of malate from whole root systems of 14 d old seedlings (8 h, 50 µM Al supply). Regression analysis revealed that the degree of Al resistance of the triticale genotypes was closely related to the Al‐induced citrate exudation, which was mainly controlled by the Al resistance of the wheat parent.

A Second Mechanism for Aluminum Resistance in Wheat Relies on the Constitutive Efflux of Citrate from Roots

“…The current study provides a detailed characterization of citrate efflux from wheat roots. We have extended the work of Stass et al (2008) by demonstrating that citrate efflux actually occurs constitutively in Carazinho and several other highly Alresistant Brazilian cultivars. This finding contrasts with the citrate efflux characterized in other cereal species such as barley, sorghum, and maize where the citrate efflux is activated by Al in much the same way that malate efflux is activated from Al-resistant wheat plants (Pellet et al, 1995;Furukawa et al, 2007;Magalhaes et al, 2007).…”

“…Our results demonstrate that Al resistance is a multigenic trait in some genotypes and that these genes do not necessarily act by modifying the function of TaALMT1. Stass et al (2008) first reported citrate efflux from the roots of Carazinho while investigating the Al resistance of triticale. They found that citrate was activated by Al treatment and that the wheat parent could influence the Al resistance of progeny from wheat/ Figure 8.…”

“…For instance, the Alactivated efflux from sorghum is encoded by SbMATE (Magalhaes et al, 2007), and citrate efflux from barley is encoded by HvAACT1, also designated as HvMATE1 (Furukawa et al, 2007;Wang et al, 2007). More recently, Stass et al (2008) reported Al-activated citrate efflux from roots of the highly resistant Brazilian wheat cultivar Carazinho and suggested that it can influence the Al resistance of triticale (3Triticosecale Wittmack) generated from crosses between Carazinho and rye.…”

The abiotic stress response and adaptation of triticale — A review

“…The amount of organic acid anions secreted was correlated positively with relative root elongation and negatively with Al content in root apices under Al stress, suggesting that the secretion of malate and citrate seems to be involved with the exclusion of Al from root tips. Eight primary octoploid triticale genotypes derived from four common wheat cultivars and two rye lines differing in Al tolerance were tested for Al tolerance (Stass et al 2008). It was concluded that the degree of Al tolerance of the triticale genotypes was closely related to the Al-induced citrate exudation, which was mainly controlled by the tolerance of the wheat parent.…”

Physiology and Biochemistry of Aluminum Toxicity and Tolerance in Crops

“…Recently, it has been also identified that the N-domain of TaALMT1 mediates ion transport even in the absence of the C-domain (Ligaba et al 2013). Other homologues of TaALMT1 such as AtALMT1 from Arabidopsis thaliana (Hoekenga et al 2006), BnALMT1 and BnALMT2 from rape (Brassica napus; Ligaba et al 2006), and ScALMT1 from rye (Seceale cereale; Li et al 2000;Stass et al 2008) have been identified that confer Al-activated malate efflux (Table 2.2).…”