Exploring the Potential of Zinc-Solubilizing Bacillus Strains to Enhance Rice (Oryza sativa L.) Productivity in Nutrient-Deficit Soils

Maqshoof Ahmad^1*Iqra Naseer¹Farheen Nazli²Hesham Sayed Ghazzawy^3*Mohamed S Sheteiwy^4*Abubakar Dar¹Rubab Sarfraz⁵Usman Zulfiqar⁶Nazih Y Rebouh⁷Xasanboy Rasulov⁸

• ¹Department of Soil Science, The Islamia University of Bahawalpur, Bahawalpur, Pakistan
• ²Institute of Agro-industry and Environment, The Islamia University of Bahawalpur, 63100,, Bahawalpur, Pakistan
• ³Date Palm Research Center of Excellence, King Faisal University, Al-Ahsa 31982, Al-Ahsa, Saudi Arabia
• ⁴Department of Integrative Agriculture, College of Agriculture and Veterinary Medicine, Al-Ain, United Arab Emirates University, Abu Dhabi 15551,, Abu Dhabi, United Arab Emirates
• ⁵Institute of Agriculture & Applied Life Science, Gyeongsang National University, Jinju, 52828, Republic of Korea, Jinju, Republic of Korea
• ⁶Department of Agronomy, Faculty of Agriculture and Environment, The Islamia University of Bahawalpur-63100, Bahawalpur, Pakistan
• ⁷Department of Environmental Management, Institute of Environmental Engineering, RUDN University, Miklukho-Maklaya St., 117198 Moscow,, Moscow, Russia
• ⁸Tashkent State Agrarian University, Department of Agrochemistry and Soil Science, 2A Universitet Str., Kibray district, 100700, Tashkent region,, Tashket, Uzbekistan

Food and nutritional security remain a significant challenge among the food-insecure people around the world, facing a lack of nutritious food rather than food availability alone. Micronutrient deficiencies in staple grains present a serious public health issue, especially impacting millions of women and children in developing nations. Staple cereals contain low concentrations of micronutrients, especially zinc (Zn). The present study explored the potential of zinc-solubilizing Bacillus strains to improve rice (Oryza sativa L.) growth, antioxidant activity, yield, and quality in a completely randomized design (CRD) with four replications. For this purpose, four preisolated, characterized and identified Bacillus strains (AN24, AN30, AN31, and AN35) were evaluated separately, as well as in co-inoculation on the growth promotion of rice cultivar PK 386. The results showed that the co-inoculation of Bacillus strains improved the growth and yield of rice more effectively than individual bacterial strains. Furthermore, co-inoculation was also more efficient in improving the soil nutrient status and biology (microbial populations) on which rice plants were grown in the pot experiment. In addition to improvement in plant growth parameters, the co-inoculation of Bacillus strains improved the N, P, K, Fe. and Zn up to 26, 30, 29, 19, and 27%, respectively, in rice grains as compared to control, along with improvement in macro and micronutrients in rice straw and roots. Co-inoculation also improved the crude protein in rice grains by 27% compared to the un-inoculated control. These results suggest that co-inoculated Bacillus megaterium strains AN24 and B. AN31offer a promising, eco-friendly alternative to synthetic fertilizers and can play a vital role in addressing micronutrient deficiencies in cereals. Further molecular characterization of Zn solubilizing genes and field-scale evaluations are recommended to validate their efficacy under diverse agroecological conditions. The combination could be further evaluated as a valuable tool for developing biofertilizers to improve rice productivity and quality in nutrient-deficient soils. 1 Introduction The global human population has been increasing rapidly, particularly during the past two