Soil-Applied Boron Combined with Boron-Tolerant Bacteria (Bacillus sp. MN54) Improve Root Proliferation and Nodulation, Yield and Agronomic Grain Biofortification of Chickpea (Cicer arietinum L.)

Noman Mehboob,Waqas Ahmed Minhas,Tauqeer Ahmad Yasir,Shahid Farooq,Ali Tan Kee Zuan,Muhammad Naveed,Mubshar Hussain,Saleh Alfarraj

doi:10.3390/su13179811

Abstract

Chickpea is widely cultivated on calcareous sandy soils in arid and semi-arid regions of Pakistan; however, widespread boron (B) deficiencies in these soils significantly decreases its productivity. Soil application of B could improve chickpea yield and grain-B concentration. However, optimizing suitable B level is necessary due to a narrow deficiency and toxicity range of B. Nonetheless, the co-application of B-tolerant bacteria (BTB) and synthetic B fertilizer could be helpful in obtaining higher chickpea yields and grain-B concentration. Therefore, this study optimized the level of soil applied B along with BTB, (i.e., Bacillus sp. MN54) to improve growth, yield and grain-B concentrations of chickpea. The B concentrations included in the study were 0.00 (control), 0.25, 0.50, 0.75 and 1.00 mg B kg−1 soil combined with or without Bacillus sp. MN54 inoculation. Soil application of B significantly improved root system, nodulation, yield and grain-B concentration, and Bacillus sp. MN54 inoculation further improved these traits. Moreover, B application at a lower dose (0.25 mg B kg−1 soil) with BTB inoculation recorded the highest improvements in root system (longer roots with more roots’ proliferation), growth, nodulation and grain yield. However, the highest grain-B concentration was recorded under a higher B level (0.75 mg B kg−1 soil) included in the study. Soil application of 0.25 mg B kg−1 with Bacillus sp. MN54 inoculation improved growth and yield-related traits, especially nodule population (81%), number of pods plant−1 (38%), number of grains plant−1 (65%) and grain yield (47%) compared with control treatment. However, the grain-B concentration was higher under the highest B level (1.00 mg kg−1 soil) with Bacillus sp. MN54 inoculation. In conclusion, soil application of 0.25 mg B kg−1 with Bacillus sp. MN54 inoculation is a pragmatic option to improve the root system, nodule population, seedling growth, yield and agronomic grain-B biofortification of chickpea.

Highlights

Macro- and micronutrients are essential for optimum plant growth, and their availability has significant impact on crop performance [1]
55–95 days after sowing (DAS) were significantly altered by B application, B-tolerant bacteria (BTB) inoculation and their interaction, while the B–BTB inoculation interaction had a non-significant effect on the chlorophyll index and leaf area (Table 1)
BTB inoculation recorded the highest number of roots per plant−1, root length, root dry weight and plant height compared to the rest of the treatments

Summary

Introduction

Macro- and micronutrients are essential for optimum plant growth, and their availability has significant impact on crop performance [1]. Boron (B) is a non-metal element and Warington [2] was the pioneer scientist who described it as a micronutrient for the first time during 1923. It plays an important role in human metabolic activities and is highly important for humans [3], animals [4] and unicellular eukaryotes at varying levels [5]. Plants require B in minute quantities; it plays significant role in plant metabolic activities It helps in stabilizing plant cell walls, membrane integrity, sugar transport and utilization of calcium and nitrogen [6,7,8]. Kanwal et al [12]

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Discussion

Conclusion