Arsenite-tolerant bacteria protect grape plants from arsenic

FUNES PINTER, M. I.; SALOMÓN, M. V.; BERLI, F.; MAZZUCCO, A.; PICCOLI, P. N.; BOTTINI, R. A.

La Falda, Córdoba

Workshop; II LATIN AMERICAN PGPR WORKSHOP; 2014

Universidad Nacional de Río Cuarto y Universidad Nacional de Quilmes

Arsenic (As) is widely spread over aquatic and terrestrial ecosystems and it constitutes an environmental treat worldwide. Many studies report As tolerant bacteria as a potential solution to remediate soils or to minimize the effects of high As concentration on plants by enhancing their tolerance to heavy metals. We previously isolated Pseudomonas fluorescens Rt6M10, Bacillus licheniformis Rt4M10 and Micrococcus luteus Rz2M10 from roots and rhizosphere of grapevines in a commercial vineyard (Salomon et al. 2013), which re-colonized roots of in vitro grown Vitis vinifera cv. Malbec plants. These bacteria were classified as plant growth promoting rhizobacteria (PGPR) since they produce the phytohormones abscisic acid (ABA), indole-3-acetic acid (IAA) and gibberellins A 1 and A 3 in chemically-defined medium, and synthesize siderophores and volatile organic compounds (VOCs). They are also tolerant to As at different pH (Funes Pinter et al. 2013). M. luteus was the most As-tolerant bacteria (40 mM NaAsO 2 at pH 9), and produced siderophores even in presence of As. It also increased and modified the VOCs profile (aliphatic and ketones) so the strain was selected as a potential candidate to be used for rhizo-remediation in As polluted vineyards. In the present study the effects of the three above mentioned As-tolerant bacteria on grapevines cv. Malbec exposed to the metalloid were analyzed. Greenhouse experiments were carried out using grapevine plants obtained from rootstock, in 10 L pot filled with sterilized sand:perlite (1:1). The treatments were: control (irrigated with water); +As (irrigated with 10 µM NaAsO 2 ); +Bli (inoculated with B. licheniformis); Bli + As (inoculated with B. licheniformis and irrigated with 10 µM NaAsO 2 ); +Mlu (inoculated with M. luteus); Mlu + As (inoculated with M. luteus and irrigated with 10 µM NaAsO 2 ); Pfl (inoculated with P. fluorescens); Pfl + As (inoculated with P. fluorescens and irrigated with 10 µM NaAsO 2 ); irrigation kept soil humidity at field capacity; plants were bacterized every week. After 3 months plants were harvested and physiological parameters were evaluated.The results indicate that PGPR bacterization improved As tolerance of grape plants. Total plant FW was higher in Bli + As respect to +As, and similar as compared with control. Net photosynthesis (PN) assessed by CO 2 fixation was highly affected by As, but this effect was reversed by bacterization, in correlation with chlorophyll content as determined by SPAD index. Oxidative damage assessed as MDA content in leaves was enhanced by As but reversed by bacterization. Proline levels were higher in + As, irrespective bacteria were present or not.The results suggest that PGRP inoculation are potentially useful to protect grape plants against As.