Chickpea (Cicer arietinum L.) as model legume for decoding the co-existence of Pseudomonas fluorescens and Mesorhizobium sp. as bio-fertilizer under diverse agro-climatic zones

Microbial co-inoculation strategy utilizes a combination of microbes to stimulate plant growth concomitant with an increased phytopathogen tolerance. In the present study, 15 endophytic bacterial isolates from rhizosphere and roots of wild chickpea accessions (Cicer pinnatifidum, C. judiacum, C. bijugum and C. reticulatum) were characterized for morphological, biochemical and physiological traits. Two promising isolates were identified as Pseudomonas fluorescens strain LRE-2 (KR303708.1) and Pseudomonas argentinensis LPGPR-1 (JX239745.1) based on 16S rRNA gene sequencing. Biocompatibility of selected endophytes with Mesorhizobium sp. CH1233, a standard isolate used as a national check in All India Coordinated Research Project (AICRP) was assessed to develop functional combinations capable of producing Indole acetic acid, gibberellins, siderophores and improving seed vigour (in vitro). In vivo synergistic effect of promising combinations was further evaluated under national AICRP, (Chickpea) at two different agro-climatic zones [North-West plain (Ludhiana and Hisar) and Central zones (Sehore)] for three consecutive Rabi seasons (2015-18) to elucidate their effect on symbiotic, soil quality and yield parameters. On the pooled mean basis across locations over the years, combination of Mrh+LRE-2 significantly enhanced symbiotic, soil quality traits and grain yield over Mrh alone and highly positive correlation was obtained between the nodulation traits and grain yield. Superior B: C ratio (1.12) and additional income of Rs 6,505.18 ha-1 was obtained by application of Mrh+LRE-2 over Mrh alone and uninoculated control. The results demonstrate that dual combination of Mrh and Pseudomonas sp. from wild Cicer relatives can be exploited as a potential bio-fertilizer for increasing soil fertility and improving chickpea productivity under sustainable agriculture.

Automated summary

The study identified promising Pseudomonas isolates from wild chickpea, which showed compatibility with Mesorhizobium sp. CH1233 and potential for producing plant growth-regulating substances. Field experiments demonstrated that the combination of Mrh+LRE-2 significantly improved symbiosis, soil quality, and yield, suggesting its potential as a bio-fertilizer for enhancing chickpea productivity under sustainable agriculture.