Legume-bacteria interactions as a biotechnological tool to avoid crop grain contamination

BIANUCCI ELIANA

Otro; Asamblea general de la Sociedad Eslovena de Biología de Plantas; 2021

Peanut, also known as groundnut, is considered the 13th most important food crop in the world and Argentina is top peanut exporting countries followed by India and the USA. This legume engages in a symbiotic interaction with rhizobia, resulting in the formation of specialized root nodules where fixation of atmospheric nitrogen takes place. Approximately 90% of the Argentinian production of peanut is located in Córdoba province, where 90% of the groundwater of the region is contaminated with arsenic (As). This is a harmful metalloid that can be naturally present in soil and groundwater. The latter is the most common source of human poisoning with As. Furthermore, ingestion of As-contaminated food is currently receiving much attention, since crops can take up the metalloid either from As-contaminated groundwater or from As-contaminated water used in artificial irrigation. Moreover, the increased occurrence of flooding episodes has aggravated the situation since groundwater could easily reach rhizosphere level. This issue constitutes not only an agronomic problem through negative effects on grain quality and yield, but also a serious risk for human health. Some peanut seeds, harvested from areas where groundwater was close to the rhizosphere level, As concentration exceeded the maximum allowed limit (0.1 mg As kg−1) set by the Codex Alimentarius Commission. Therefore, the aim of our work is to evaluate effect of As on peanut plants at biochemical and morpho-physiological level in order to find strategies to avoid seed contamination. One of the first studies carried out in our laboratory to decrease As concentration in plants was to identify peanut microsymbiont exhibiting strongest reduction of As mobility in peanut. Results indicated Bradyrhizobium sp. SEMIA6144 was the rhizobia that reduced As translocation to shoots by improving metalloid phytostabilization in roots and nodules best in comparison to other species tested. However, peanut growth, nodulation and nitrogen content were significantly reduced. In addition, it is known that arsenate is a chemical analogue of phosphate (P), and its cellular uptake is mediated by phosphate transporters. For that, we inoculated peanut with native solubilizing phosphate bacteria (PSB) and the rhizobia. PSB acted as a helper microorganism to rhizobia by increasing P and N content and therefore, improving peanut growth under this unfavourable growth condition. Field experiments are being carried out to further elucidate the effect of As on peanut crop.