Alleviation of Drought Stress in Zea Mays Seeding by Extracellular Polysaccharides Produced by Azotobacter

Abstract

Azotobacter bacteria are Gram-negative, rod-shaped soil bacteria that can fix atmospheric nitrogen and promote plant growth. They are known to produce exopolysaccharides (EPS), which can help plants to retain water and tolerate drought stress. In this study, 20 Azotobacter isolates were isolated from dry and semi-dry soil samples. The isolates were characterized morphologically and microscopically and tested for their tolerance to drought using PEG6000 at concentrations of 0%, 5%, 10%, 15%, 20%, and 25%. They were also tested for their ability to produce EPS. The isolates that were most tolerant to drought and produced the most EPS were used as biofertilizers to improve the drought tolerance of maize seedlings. The seedlings were irrigated every 24, 48, or 72 hours. The results showed that the biofertilizers containing the two most drought-tolerant and EPS-producing Azotobacter isolates (Azotobacter 1 and Azotobacter 2) significantly improved the germination rate, dry weight, stress tolerance index, chlorophyll stability, and membrane damage index of the maize seedlings.