Abstract
The present study was designed to screen the Mesorhizobium strains (50) for tolerance with four recommended pesticides in chickpea. In-vitro, robust pesticide tolerant strains were developed in pesticides amended media over several generations. Further, verification of the multifunctional traits of pesticide tolerant mesorhizobia under pesticide stress was conducted in-vitro. Among different pesticides, significantly high tolerance in Mesorhizobium strains was observed with recommended doses of pendimethalin (37%) and ready-mix (36%) followed by chlorpyrifos (31%) and carbendazim (30%), on an overall basis. Based on multifunctional traits, Mesorhizobium strains viz. MR2, MR17 and recommended MR33 were the most promising. Ecological performance of the potential Mesorhizobium strains alone and in dual-inoculation with recommended PGP rhizobacterium strain RB-1 (Pseudomonas argenttinensis JX239745.1) was subsequently analyzed in field following standard pesticide application in PBG-7 and GPF-2 chickpea varieties for two consecutive rabi seasons (2015 and 2016). Dual-inoculant treatments; recommended RB-1 + MR33 (4.1%) and RB-1 + MR2 (3.8%) significantly increased the grain yield over Mesorhizobium alone treatments viz MR33 and MR2, respectively. Grain yield in PBG7 variety was significantly affected (7.3%) by the microbial inoculant treatments over GPF2 variety. Therefore, the potential pesticide tolerant strains MR2 and MR33 can be further explored as compatible dual-inoculants with recommended RB-1 for chickpea under environmentally stressed conditions (pesticide application) at multiple locations. Our approach using robust multifunctional pesticide tolerant Mesorhizobium for bio-augmentation of chickpea might be helpful in the formulation of effective bio-inoculants consortia in establishing successful chickpea-Mesorhizobium symbiosis.
Highlights
Chickpea is the most important rabi pulse crop of India with an increase in production from 6.5 million tonnes to 10.3 million tonnes and grain yield from 630 to 935 Kg ha-1 during the past 35 years (Singh et al 2018)
The potential pesticide tolerant strains MR2 and MR33 can be further explored as compatible dual-inoculants with recommended RB-1 for chickpea under environmentally stressed conditions at multiple locations
Four recommended pesticides viz. pre-emergence and pre-plant, insecticide and fungicide were tested with selected mesorhizobia strains for tolerance to single (1×) and double (2×) the recommended doses of pesticides (Table 1) using the disc diffusion method
Summary
Chickpea is the most important rabi pulse crop of India with an increase in production from 6.5 million tonnes to 10.3 million tonnes and grain yield from 630 to 935 Kg ha-1 during the past 35 years (Singh et al 2018). Is under wide practice to improve the yield by enhancing root nodulation and N uptake of the plant. Inoculation of chickpea seeds with a selected strain of Mesorhizobium sp. This helps in reducing the dependency on chemical fertilizers (Brigido et al 2017). Co-inoculation of plant growth-promoting (PGP) bacteria with Rhizobium synergistically improves the legume growth, symbiotic nitrogen fixation (SNF), yield, and overall plant’s performance by absorption of nitrogen, phosphorus and other macro-and micronutrients (Gopalakrishnan et al 2015). The robust strains of Mesorhizobium with multifunctional traits were explored for ecological performance on plant growth, SNF and yield in chickpea crop raised with the recommended application of pesticides under field conditions
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