Location: Plant, Soil and Nutrition ResearchTitle: Evaluation of aluminum tolerance in grapevine rootstocks Author
Submitted to: Vitis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2009
Publication Date: 9/7/2009
Citation: Cancado, G., Ribeiro, P., Pineros, M., Myiata, L., Alvarenga, A., Villa, F., Pasqual, M., Purgatto, E. 2009. Evaluation of aluminum tolerance in grapevine rootstocks. Vitis. 48(4):167-173. Interpretive Summary: Approximately 50% of the world’s arable lands are acidic (pH < 5). On these acid soils, aluminum (Al) toxicity is the primary factor limiting crop production as Al is toxic to plant roots, leading to a damaged and stunted root system. As a large proportion of the acid soil are in the tropics/subtropics where many developing countries are located, Al toxicity limits crop production in the very areas where food security is most tenuous. In Brazil, agriculture in acidic soil regions with elevated concentration of Al has significantly increased in the last decades. Although grape production for winemaking in Brazil was exclusively restricted to the southern subtropical region, nowadays the production of this agronomical important crop has spread to tropical regions, which are characteristically acidic and highly saturated with toxic levels of aluminum. Screening the genetic diversity in grapevine rootstocks to improve its performance of this type of soil is highly needed. In the present study, we evaluated the physiological mechanism(s) that grant grapevines improved agricultural performance in highly acid soils. Six genotypes of grapevine rootstocks regularly cultivated in Brazil were evaluated in terms of their Al resistance, as an initial approach to develop new genotypes with improved Al-resistance. The results indicated that the Al resistance recorded for two of the grapevine genotypes is quite likely achieved via similar physiological mechanisms to those described in other crop species. Exudation of organic anion capable of binding and immobilizing Al at the root prior to penetrating the root, quite likely underlies the Al-resistance phenotypes in these genotypes.
Technical Abstract: Aluminum (Al) toxicity is a major worldwide agricultural problem. At low pH, Al speciates into the soluble and phyto-toxic form Al3+, causing inhibition of root growth and affecting plant development. In Brazil, agriculture in acidic soils regions with elevated concentration of Al has significantly increased in the last decades. Therefore, in order to achieve efficient agriculture practices, the selection of plant cultivars with improved Al resistance has become crucial in this type of soils. In this work, we have evaluated the Al resistance of six genotypes of grapevine rootstocks regularly cultivated in Brazil. The grapevine plantlets were grown in nutrient solution in the absence and presence of 250 and 500 uM Al at pH 4.2. The phenotypic indexes of relative root growth, fresh and dry root weight, root area, hematoxylin staining profile, and Al content were evaluated for all six genotypes. These phenotypic indexes allowed us to identify the Kobber, Gravesac, Paulsen 1103, and IAC 766 grapevine rootstocks genotypes as the ones with the highest resistance to Al. Likewise, IAC 572 and R110 genotypes were the most Al-sensitive cultivars. We evaluated the root organic acid exudation profile in the most Al-resistant (Kobber) and most Al-sensitive (R110) in plants cultivated in vitro in the absence and presence of 100, 200, and 400 uM of Al. Among several compounds detected, citrate was the only organic acid related to the Al resistance phenotype observed in the Kobber genotype. The high constitutive citrate exudation observed in Kobber strongly suggests that exudation of this particular organic acid may impart Al resistance/ amelioration.