Abstract
Stress drought is an important abiotic factor that leads to immense losses in crop yields around the world. Strategies are urgently needed to help plants adapt to drought in order to mitigate crop losses. Here we investigated the bioprotective effects of inoculating corn grown under drought conditions with two types of plant growth-promoting rhizobacteria (PGPR), A. brasilense, strain SP-7, and H. seropedicae, strain Z-152. Plants inoculated with the bacteria were grown in a greenhouse with perlite as a substrate. Two hydric conditions were tested: normal well-watered conditions and drought conditions. Compared to control non-inoculated plants, those that were inoculated with PGPR bacteria showed a higher tolerance to the negative effects of water stress in drought conditions, with higher biomass production; higher carbon, nitrogen, and chlorophyll levels; and lower levels of abscisic acid and ethylene, which are plant hormones that affect the stress response. The oxidative stress levels of these plants were similar to those of non-inoculated plants grown in well-watered conditions, showing fewer injuries to the cell membrane. We also noted higher relative water content in the vegetal tissue and better osmoregulation in drought conditions in inoculated plants, as reflected by significantly lower proline content. Finally, we observed lower gene expression of ZmVP14 in the inoculated plants; notably, ZmVP14 is involved in the biosynthesis of abscisic acid. Taken together, these results demonstrate that these bacteria could be used to help plants cope with the negative effects of drought stress conditions.
Highlights
Corn (Zea mays L.) farming is one of the most important and extensive farming systems in the world because of the myriad products derived from this plant
The first factor, bacteria, had three levels: (1) control seeds treated with sterile NFb medium [59]; (2) seeds inoculated with Azospirillum brasilense, strain SP-7 (ATCC 29729TM); and (3) seeds inoculated with Herbaspirillum seropedicae, strain Z-152 (ATCC 35894TM)
In the D condition, plants inoculated with H. seropedicae showed 29.5% greater Total Biomass (TB) production than control plants, and plants inoculated with A. brasilense showed 26% greater TB production than control plants
Summary
Corn (Zea mays L.) farming is one of the most important and extensive farming systems in the world because of the myriad products derived from this plant. In 2013, a total of 1,018,111,958 tons of corn were produced globally [1]. Drought is a major abiotic stress factor that affects crop yield. The loss in crop yield during drought depends on the phenological stage of the crops and on the severity of the hydric deficit [3]. Global warming is predicted to increase the severity and the frequency of drought. According to Food and Agriculture Organization of the United Nations (FAO), the Food and Agriculture Organization of the United Nations, agriculture must adapt to the effects of global warming and improve crop resilience in order for food production to meet the food needs of our increasing population. The production of major crops will have to shift to marginal areas, some with hydric deficits [4]
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