Assessment of zinc-solubilizing bacterial isolates for plant growth promoting traits and water stress tolerance behaviour

The present study elucidates the efficiency of zinc solubilization and the plant growth-promoting (PGP) traits exhibited by selected zinc-solubilizing bacterial (ZSB) strains. Qualitative analysis unveils distinct variations in solubilization efficiency, with isolate FMBR110 demonstrating exceptional proficiency in solubilizing zinc from various insoluble sources. PGP traits, encompassing phosphate solubilization, siderophore production, indole-3-acetic acid (IAA) synthesis, exopolysaccharide (EPS) generation, hydrogen cyanide (HCN) emission, and ammonia production are quantified, spotlighting the functional diversity among isolates. Notably, FMAR106 showed the highest phosphate solubilization zone value (2.20 cm), while FMBR110 exceled in siderophore production (4.37 cm halo zone), IAA synthesis (24.09 µg/ml), and stands out as the sole producer of HCN. Furthermore, isolate FMBR110, exhibited remarkable tolerance to water stress, even in high water saturated soil conditions. The study accentuates the importance of selecting ZSB strains tailored to specific water conditions in agriculture, offering promising solutions for sustainable crop production, particularly in high water-stressed regions or flooding conditions.

Illustrations explain the paper; charts are replotted from the paper's own table values.

AI-generated illustration

↗ Enlarge

Soil Moisture Treatment SetupClose ×

AI-generated conceptual illustration (tomato plants in glass containers with soil). It explains the idea and does not show study data.

Open full-size image ↗

Replotted from source data

↗ Enlarge

Zinc sources / ZnO (Zinc Oxide) / Zone (cm) and ZnCO3 (Zinc Carbonate) / Zone (cm) and more: FMBR75 vs FMAR106 vs FMBR110 vs FMAR119 vs BMRR128Close ×

Replotted from Table 1 (page 3) of the original paper. Every bar is the paper's own table value.

Open full-size image ↗

Replotted from source data

↗ Enlarge

FMBR75: Phosphate... vs Siderophore production vs IAA Production (µg/ml) vs Quantitative EPS...Close ×

Replotted from Table 2 (page 3) of the original paper. Every bar is the paper's own table value.

Open full-size image ↗

Introduction

Zinc (Zn) deficiency in crops poses a widespread global challenge, endangering both food security and nutrition. This dearth, often referred to as "hidden-hunger," distresses more than two billion people worldwide (Lowe, 2021) [10] , particularly those who rely on main crops like rice, wheat, and maize (Upadhayay et al., 2018) [24] . Zn is a crucial micronutrient essential for both plant growth and human health, playing a pivotal role in various physiological processes (Upadhayay et al., 2019; 2022a, 2022b 2022c, 2022d) [28,20,23,26,27] . Addressing Zn deficiency in crops demands ground-breaking agricultural strategies, and one promising approach involves harnessing the power of Zn-solubilizing bacteria (ZSB) (Khan et al., 2019, Upadhayay et al. 2021) [9,25] . These outstanding microorganisms possess a unique ability to solubilize insoluble Zn compounds in the soil, thereby making this vital nutrient readily accessible to plants (Kamran et al. 2017; Singh et al., 2022) [6,18] . By enhancing Zn uptake, ZSB have the potential not only to maximize crop yields but also to improve the nutritional quality of food, ultimately mitigating hidden hunger (Upadhayay et al., 2022d) [27] . Furthermore, ZSB exhibit various plant growth-promoting traits such as phosphate solubilization, production of IAA, siderophore, EPS, and more, exhibiting their promising application as bioinoculants (Bhatt and Maheshwari, 2020; Upadhayay et al., 2022b, 2023a, 2023b) [1,23,21,22] . While the application of ZSB for Zn biofortification holds great promise, their performance under different environmental conditions, particularly varying moisture levels, is a critical aspect that requires thorough examination. Understanding how ZSB respond to varying moisture conditions is crucial for unlocking their full potential in addressing Zn deficiency and enhancing crop resilience in the face of water stress-related challenges. Therefore, there is a need to develop a robust methodology for assessing the water tolerance of selected ZSB strains.

Materials and Methods

Materials and Methods

Isolation of Bacteria

Soil samples were collected from three hilly regions in Uttarakhand: Almora, Bhowali, and Ranichauri. These samples were taken from the rhizospheres of finger millet and barnyard millet plants. The collected soil was stored in sterile polythene bags at 4 °C. For bacterial isolation, 1g of soil from each rhizosphere was mixed with 10 ml of sterile saline solution and diluted (ranging from 10 -1 to 10 -5 ). Aliquots (100μl) from each dilution were plated on nutrient agar and incubated at 28±2 °C until distinct colonies formed. Selected colonies were purified using the 'four-waystreaked procedure' on nutrient agar plates.

Zinc Solubilization Bioassay

The study screened potential ZSB isolates by following procedure of Ramesh et al. (2014) [14] . Mineral salt medium was prepared with insoluble zinc compounds (ZnO, Zn 3 (PO 4 ) 2 , ZnCO 3 ), autoclaved, and poured into Petri plates. Overnight-grown test isolates were spot-inoculated on mineral salt media plates supplemented with insoluble zinc compounds (ZnO, Zn 3 (PO 4 ) 2 , ZnCO 3 ), and plates were sealed with parafilm and incubated at 28 °C for a week. The appearance of a halo zone around bacterial colonies indicated positive results. Zinc solubilization efficiency (S.E) was calculated using the formula: Zn S.E. = diameter of solubilization halo/diameter of the colony×100

In vitro Screening of Plant Growth Promoting Traits

The phosphate solubilization potential of the bacterial isolates was quantitatively assessed following the method described by Nautiyal (1999) [12] . The synthesis of the plant hormone indole-3-acetic acid (IAA) by the bacterial strains was analyzed following the procedure of Patten and Glick (2002) [13] . Siderophore production, which involves the production of iron-chelating agents, was estimated using 'Chrome-Azurol S (CAS) medium' following the method of Schwyn and Neilands (1987) [16] . CAS agar plates were spot-inoculated with bacterial culture, and after 4 days of incubation at 28±2 °C, siderophore production was confirmed based on the measurement of the yellow-orange halo zone that appeared around the bacterial colony. The EPS production ability of bacterial isolates was performed by following method of Siddikee et al. (2011) [17] . After 5 days of incubation at 28±2 °C, the supernatant was mixed with chilled ethanol for precipitation, and the dry residue weight was measured in mg/ml. For ammonia production, bacterial cultures were incubated in peptone water, and ammonia was detected using Nessler's reagent following method of Cappuccino and Sherman (1992) [2] .

Water stress tolerance assay

In this study, we conducted an experiment to evaluate the water tolerance of selected zinc-solubilizing bacterial (ZSB) strains under a range of moisture conditions. The soil used for this experiment was collected from the Crop Research Centre (CRC) at G.B. Pant University of Agriculture and Technology, Pantnagar. To ensure its sterilization, the soil underwent a thorough sterilization process over three consecutive days. For the experiment, plastic disposable glasses with a capacity of 300 mL each were employed. These glasses were cleaned with 70% ethanol and then subjected to sterilization under UV light for two hours. Each of the glasses was filled with 100 grams of the sterilized soil. To create different moisture conditions, five distinct treatments were established by adding distilled water (DW) to each cup as follows:

1. Glass 1: The soil in the first cup was saturated by adding 28ml of distilled water.

Glass 2:

The soil in the second cup was maintained at 60% moisture level by adding 9.3ml of water to achieve this level.

Glass 3:

The soil in the third cup was saturated with water, and the cup was filled with DW from the soil's upper surface to a height of 2 cm.

Glass 4:

The soil in the fourth cup was saturated with distilled water, followed by filling the cup with DW from the soil's upper surface to a height of 5 cm.

Glass 5:

The soil in the fifth cup was first saturated with sterilized distilled water, followed by filling the cup with DW from the soil's upper surface to a height of 10 cm.

To introduce the ZSB strains, a 4 mL aliquot of an overnight-grown bacterial culture was added to each glass.

To prevent contamination, each glass was covered with parafilm and aluminum foil and then incubated at room temperature. Sampling was conducted on the 7th, 14th, and 21 st days of the experiment. From each glass, 1 gram of soil was sampled and subjected to Colony-Forming Unit (CFU) counting using the standard pour plate method on nutrient agar media. The moisture tolerance of the selected ZSB strains was assessed based on the number of colonies, categorized as less than 30, between 30-300, or more than 300 colonies, at three different dilutions (10 -3 , 10 -5 , and 10 -7 ) on various days (7 th , 14 th , and 21 st days) under different soil moisture conditions. This comprehensive methodology allowed us to evaluate the water tolerance of these ZSB strains, shedding light on their performance, particularly in water-stressed environments.

Results and Discussion

The results, summarized in the [3,6,7] . Zinc plays a crucial role in plant growth, and the ability of soil microorganisms to solubilize this essential nutrient is a critical trait. These microorganisms employ various mechanisms to convert zinc into a soluble form, making it readily available to crop plants (Upadhayay et al., 2018) [24] . The functional traits of the selected bacterial isolates, including phosphate solubilization, siderophore production, indole-3-acetic acid (IAA) production, quantitative exopolysaccharide (EPS) production, hydrogen cyanide (HCN) production, and ammonia production are depicted in table 2. The results unveiled a spectrum of functional diversity among the isolates. Notably, FMAR106 displayed a larger phosphate solubilization halo zone (2.20±0.20 cm). Furthermore, FMBR110 stood out with the highest siderophore production (halo zone diameter: 4.37±0.57) and IAA production (24.09±0.71 µg/ml). In contrast, FMBR206 exhibited relatively high EPS production (2.36±0.26 mg/ml). Interestingly, hydrogen cyanide production was solely detected in FMBR110. Ammonia production trait was evident in FMAR106, FMBR110, FMAR119, and FMBR206, while absent in the other isolates. The production of siderophores by these isolates indicates their capacity to enhance the solubilization of iron (Jaiswal et al., 2023) [5] , making them valuable as bio-inoculants for iron-fortified crop production (Upadhayay et al., 2018) [24] . Additionally, their ability to solubilize phosphate is crucial for crop revitalization. This aspect is consistent with earlier findings, such as those by Bhatt and Maheshwari et al.

S. No.	Bacterial isolate	Phosphate solubilization	Siderophore production	IAA Production (µg/ml)	Quantitative EPS production (mg/ml)	HCN production	Ammonia production
		Halo zone Diameter (cm)
1.	FMBR75	1.30±0.10	2.77±0.12	7.21±0.69	1.13±0.09	-	-
2.	FMAR106	2.20±0.20	2.63±0.15	6.92±1.45	1.02±0.07	-	+
3.	FMBR110	1.30±0.10	4.37±0.57	24.09±0.71	1.80±0.13	+	+
4.	FMAR119	1.10±0.10	2.53±0.12	5.15±1.17	1.52±0.17	-	+
5.	BMRR128	2.17±0.21	2.57±0.12	7.38±0.9	1.23±0.13	-	-
6.	FMBR206	1.03±0.5	1.67±0.42	10.77±0.63	2.36±0.26	-	+
7.	BMBR260	0.90±0.10	2.43±0.21	10.40±0.56	0.94±0.09	-	-

Table text extracted from the original PDF; superscript letters are shown inline. The original table image is below.

View original table image

↗ Enlarge

Table 2Close ×

Plant growth promoting characteristics of zinc solubilizing bacterial isolates

Open full-size image ↗

Original paper tableSource PDF · page 3 ↗

(2020) [1] , which also identified phosphate-solubilizing properties in ZSB. This variation in IAA production aligns with previous studies involving bacterial isolates from different sources (Singh et al., 2020; Khan et al., 2022) [19,8] . Additionally, the isolates were assessed for exopolysaccharide (EPS) production, which supports efficient root colonization and nutrient absorption. Prior research has demonstrated that ZSB isolates capable of producing EPS have been used to enrich crops with zinc (Nandal and Solanki, 2021) [11] . Lastly, the isolates displayed characteristics conducive to plant growth, including ammonia production, a well-documented trait of plant growth-promoting bacteria (Roshni et al., 2020) [15] . These diverse traits highlight the potential of these isolates to and make them promising bioinoculants to enhance nutrient availability, promote plant growth, and improve soil health. The valuable insights were extracted through the systematic analysis of selected ZSB isolates, elucidating their tolerance to diverse moisture conditions across various levels of moistened soil over a 21-day timeframe (representing conditions of water stress). The results were analyzed by determining colony-forming units (CFU) at dilutions (10 -3 , 10 -5 , and 10 -7) on days 7, 14, and 21 to assess the performance of bacterial isolates (Table 3). Strain FMBR110 showed striking water tolerance behaviour, especially when the soil was saturated with water up to 10 cm from the surface. Even at the dilution of 10 -5 , the appearance of bacterial after plating indicated that this isolate thrived throughout the entire 14-day period, indicating its ability to adapt to very moist conditions. While FMAR106, BMRR128, FMBR206, and BMBR260 displayed colony counts of fewer than 30 when the soil was saturated with water up to a depth of 10 cm and studied at the 7 th day with a 10 -5 dilution. This resilience suggests that FMBR110, FMAR106, BMRR128, FMBR206, and BMBR260 could be valuable candidates for environments susceptible to water stress. This potential makes them promising candidates for improving agriculture in areas facing high water stress related challenges or flood conditions.

Soil Conditions	Dilution	Bacterial isolates	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—
		FMBR75			FMAR106			FMBR110			FMAR119			BMRR128			FMBR206				BMBR260
		7 days	14 days	21 days	7 days	14 days	21 days	7 days	14 days	21 days	7 days	14 days	21 days	7 days	14 days	21 days	7 days	14 days	21 days	7 days		14 days	21 days
WSS	10-3	H	M	L	H	M	L	H	H	H	H	M	M	H	L	L	H	M	M	M		L	L
	10-5	M	L	-	H	L	-	M	M	M	M	L	-	M	L	L	H	M	L	L		-	-
	10-7	-	-	-	L	-	-	-	L	L	-	-	-	-	-	-	-	-	-	-		-	-
MS	10-3	H	M	L	H	M	L	H	H	H	H	H	L	H	M	L	H	M	L	M		M	M
	10-5	M	L	L	M	L	-	M	M	M	H	L	L	H	M	-	H	M	-	M		M	-
	10-7	L	-	-	L	-	-	-	L	-	L	-	-	-	-	-	L	-	-	-		-	-
Wfg2	10-3	H	L	-	M	L	-	M	M	M	H	L	-	H	M	-	H	M	L	L		-	-
	10-5	L	-	-	M	L	-	L	L	L	L	-	-	M	L	-	M	L	-	-		-	-
	10-7	-	-	-	-	-	-	L	L	-	-	-	-	-	-	-	-	-	-	-		-	-
wfg5	10-3	M	L	-	M	L	-	M	M	L	L	L	-	M	L	-	H	L	-	M		M	M
	10-5	L	-	-	M	L	-	L	L	-	L	-	-	M	-	-	M	-	-	-		-	-
	10-7	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-		-	-
Wfg10	10-3	M	-	-	M	L	-	M	M	L	L	-	-	M	L	-	M	L	L	M		M	L
	10-5	-	-	-	L	-	-	L	L	-	-	-	-	L	-	-	L	-	-	L		-	-
	10-7	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-		-	-

Table text extracted from the original PDF; superscript letters are shown inline. The original table image is below.

View original table image

↗ Enlarge

Table 3Close ×

Tolerance behavior of different zinc solubilizing bacterial strains for different moisture levels

Open full-size image ↗

Original paper tableSource PDF · page 4 ↗

The strategic selection of ZSB strains has a profound impact on nutrient accessibility to plants, with the potential to significantly enhance crop growth and productivity. This influence is particularly noteworthy in regions where water stress is a prevalent concern, specifically in flooded soils.

Our findings underscore the paramount importance of meticulously choosing ZSB strains that align with the prevailing moisture conditions in a given agricultural environment, emphasizing this significance, especially in paddy fields. Notably, previous research has shown that tomato plants grown from seeds inoculated with Enterobacter and Pseudomonas putida strains expressing ACC deaminase exhibited resistance to the negative effects of flooding stress (Grichko and Glick, 2001) [4] . While our study sheds light on the water stress tolerance of these bacterial strains, further research is necessary to understand the exact mechanisms by which they adapt to different moisture levels. Additionally, field trials are needed to assess how practical and effective these strains are in realworld agricultural situations.

Conclusion

In conclusion, our study demonstrates the effectiveness of selected bacterial strains in solubilizing Zn and their diverse plant growth promoting properties (PGP). Furthermore, the bacterial isolate FMBR110, followed by FMAR106, BMRR128, FMBR206 and BMBR260, showed remarkable tolerance to water stress, especially in highly watersaturated soil conditions. The variable degrees of moisture tolerance among these strains underscore their potential to fortify crop resilience, especially in regions susceptible to flooding. Additionally, ZSB strains with high water tolerance can be a valuable asset for sustainable agriculture, especially in areas struggling with excessive moisture. To fully unlock the practical benefits of these bacteria in augmenting crop growth and productivity in water-stressed environments or flood conditions, additional research and on-field trials are imperative.

Figures and tables from the paper

Bacterial Isolates	Zinc sources	—	—	—	—	—
	ZnO (Zinc Oxide)		ZnCO3 (Zinc Carbonate)		Zn3 (PO4)2 (Zinc phosphate)
	Zone (cm)	Solubilization efficiency (%)	Zone (cm)	Solubilization efficiency (%)	Zone (cm)	Solubilization efficiency (%)
FMBR75	1.1±0.20	133.69	1.3±0.26	140.37	0.9±0.12	100.78
FMAR106	1.47±0.12	286.19	1.8±0.21	244.44	0.8±0.15	131.58
FMBR110	1.37±0.35	533.33	1.6±0.05	408.33	0.9±0.20	209.30
FMAR119	1.4±0.17	422.22	1.5±0.20	292.62	1.1±0.17	183.33
BMRR128	0.83±0.15	195.00	1.2±0.10	258.33	0.7±0.05	175.00
FMBR206	1.3±0.10	371.11	1.7±0.20	468.89	1.0±0.30	188.68
BMBR260	0.63±0.12	177.78	0.9±0.15	240.00	0.6±0.21	121.43

Table text extracted from the original PDF; superscript letters are shown inline. The original table image is below.

View original table image

↗ Enlarge

Table 1Close ×

Qualitative zinc solubilization by selected bacterial isolates using three different insoluble zinc sources (zinc oxide, zinc carbonate

Open full-size image ↗

Original paper tableSource PDF · page 3 ↗

1. Bhatt K, Maheshwari DK. Zinc solubilizing bacteria (Bacillus megaterium) with multifarious plant growth promoting activities alleviates growth in Capsicum annuum L. 3 Biotech. 2020;10(2):36. https://doi.org/10.1007/s13205-019-2033-9
2. Gontia-Mishra I, Sapre S, Tiwari S. Zinc solubilizing bacteria from the rhizosphere of rice as prospective modulator of zinc biofortification in rice. Rhizosphere. 2017;3:185-190. https://doi.org/10.1016/j.rhisph.2017.04.013
3. Grichko VP, Glick BR. Amelioration of flooding stress by ACC deaminase-containing plant growth-promoting bacteria. Plant Physiol Biochem. 2001;39(1):11-17. https://doi.org/10.1016/S0981-9428(00)01212-2
4. Jaiswal A, Kumari G, Upadhyay VK, Pradhan J, Singh H, Pramanik K. A methodology of isolation for development of PGPR consortia. Pharma Innovation. 2023;12(11):803-809.
5. Kamran S, Shahid I, Baig DN, Rizwan M, Malik KA, Mehnaz S. Contribution of Zinc Solubilizing Bacteria in Growth Promotion and Zinc Content of Wheat. Front Microbiol. 2017;8. https://doi.org/10.3389/fmicb.2017.02593
6. Khan A, Singh AV, Pareek N, Arya P, Upadhayay VK, Kumar Jugran A, Kumar Mishra P, Goel R. Credibility assessment of cold adaptive Pseudomonas jesenni MP1 and P. palleroniana N26 on growth, rhizosphere dynamics, nutrient status, and yield of the kidney bean cultivated in Indian Central Himalaya. Front Plant Sci. 2023. https://doi.org/10.3389/fpls.2023.1042053
7. Khan A, Singh AV, Kumar R, Kukreti B, Bundela V, Upadhayay VK. Relative impact of PGPR inoculation on biofortification and yield of wheat under field conditions and their performance assessment through statistical tools. Pharma Innovation. 2022;11(8):490495.
8. Lowe NM. The global challenge of hidden hunger: perspectives from the field. Proc Nutr Soc. 2021;80(3):283-289. https://doi.org/10.1017/S0029665121000902
9. Nandal V, Solanki M. Isolation screening and molecular characterization of zinc solubilizing bacteria and their effect on the growth of wheat (Triticum aestivum). Asia Pac J Mol Biol Biotechnol. 2021;85-97.
10. Nautiyal C. An efficient microbiological growth medium for screening phosphate solubilizing microorganisms. FEMS Microbiol Lett. 1999;170(1):265-270. https://doi.org/10.1016/S0378-1097(98)00555-2
11. Patten CL, Glick BR. Role of Pseudomonas putida Indoleacetic Acid in Development of the Host Plant Root System. Appl Environ Microbiol. 2002;68(8):3795-3801. https://doi.org/10.1128/AEM.68.8.3795-3801.2002
12. Ramesh A, Sharma SK, Sharma MP, Yadav N, Joshi OP. Inoculation of zinc solubilizing Bacillus aryabhattai strains for improved growth, mobilization and biofortification of zinc in soybean and wheat cultivated in Vertisols of central India. Appl Soil Ecol. 2014;73:87-96. https://doi.org/10.1016/j.apsoil.2013.08.009
13. Roshani KA, Singh AV, Upadhayay VU, Prasad B. Development of potential microbial consortia and their assessment on wheat (Triticum aestivum) seed germination. Environ Ecol. 2020;38:6-16.
14. Schwyn B, Neilands JB. Universal chemical assay for the detection and determination of siderophores. Anal Biochem. 1987;160(1):47-56. https://doi.org/10.1016/0003-2697(87)90612-9
15. Siddikee MA, Glick BR, Chauhan PS, Yim WJ, Sa T. Enhancement of growth and salt tolerance of red pepper seedlings (Capsicum annuum L.) by regulating stress ethylene synthesis with halotolerant bacteria containing 1-aminocyclopropane-1-carboxylic acid deaminase activity. Plant Physiol Biochem. 2011;49(4):427-434. https://doi.org/10.1016/j.plaphy.2011.01.015
16. Singh J, Singh AV, Upadhayay VK, Khan A, Chandra R. Prolific contribution of Pseudomonas protegens in Zn biofortification of wheat by modulating multifaceted physiological response under saline and non-saline conditions. World J Microbiol Biotechnol. 2022;38(12):227. https://doi.org/10.1007/s11274-022-03411-4
17. Singh J, Singh AV, Upadhayay VK, Khan A. Comparative evaluation of developed carrier-based bioformulations bearing multifarious PGP properties and their effect on shelf life under different storage conditions. Environ Ecol. 2020;38(1):96-103.
18. Upadhayay VK, Khan A, Singh J, Singh AV. Bacterial assisted improved zn consignment in root and shoot of rice plant by zinc solubilizing Serratia marcescence bearing plant probiotic traits. Adv Biores. 2022;13(1):108.
19. Upadhayay VK, Singh AV, Khan A. Cross Talk Between Zinc-Solubilizing Bacteria and Plants: A Short Tale of Bacterial-Assisted Zinc Biofortification. Front Soil Sci; c2022. https://doi.org/10.3389/fsoil.2021.788170
20. Upadhayay VK, Singh AV, Pareek N. An insight in decoding the multifarious and splendid role of microorganisms in crop biofortification. Int J Curr Microbiol Appl Sci. 2018;7(06):2407-2418. https://doi.org/10.20546/ijcmas.2018.706.286
21. Upadhayay VK, Singh AV, Khan A, Pareek N. Influence of zinc solubilizing bacterial co-inoculation with zinc oxide supplement on rice plant growth and Zn uptake. Pharm Innovat. 2021;10:113-116.
22. Upadhayay VK, Singh AV, Khan A, Sharma A. Contemplating the role of zinc-solubilizing bacteria in crop biofortification: An approach for sustainable bioeconomy. Front Agron; c2022. https://doi.org/10.3389/fagro.2022.903321
23. Upadhayay VK, Singh AV, Khan A, Singh J, Pareek N, Raghav A. FE-SEM/EDX Based Zinc Mobilization Analysis of Burkholderia cepacian and Pantoea rodasii and Their Functional Annotation in Crop Productivity, Soil Quality, and Zinc Biofortification of Paddy. Front Microbiol; c2022. https://doi.org/10.3389/fmicb.2022.852192