Impact of Genotype and Phosphorus Fertilization on the Occurrence of Phosphorus Solubilizers at Different Developmental Stages of Wheat
Garcha Seema *
Department of Microbiology, Punjab Agricultural University, Ludhiana, 141001, India.
Garg Shreya
Department of Microbiology, Punjab Agricultural University, Ludhiana, 141001, India.
*Author to whom correspondence should be addressed.
Abstract
This study aimed to investigate (i) how wheat genotype (landrace vs. modern cultivars) and phosphorus (P) fertilization influence the occurrence of phosphate-solubilizing bacteria (PSB) in rhizospheric soil, roots, and shoots across different developmental stages, and (ii) to characterize the functional traits of PSB isolates to identify efficient candidates for bioinoculant development. The study design of the field trails was randomized block design and it was carried out in the research fields of the Department of Plant Breeding and Genetics, College of Agriculture, Punjab Agriculture University Ludhiana Punjab. Experiments were conducted with a wheat landrace (LC306) and two modern cultivars (PBW725, HD3086) under P-amended and P-starved conditions in a randomized block design. Samples from rhizospheric soil, root, and shoot tissues were collected at four developmental stages (20-25 days after sowing DAS, 60DAS, 90DAS, and flowering). PSB were isolated on Pikovskaya’s agar and characterized for solubilization index (SI) and quantitative phosphate solubilization in broth. Efficient isolates were identified by 16S rRNA gene sequencing. Phylogenetic relationships were assessed, and morphological and biochemical traits documented. P-starved rhizospheres showed significantly higher PSB counts at early growth stages (log 6.95 cfu/g at 20-25 DAS in LC306) compared to P-amended soils. Root tissues also had higher PSB under P starvation initially, but counts declined toward flowering. Conversely, shoots had greater PSB counts under P-amended conditions. The landrace LC306 consistently harbored more PSB, especially under P stress. Among 21 isolates, SI ranged from 2.06 to 2.71, and phosphate solubilization reached up to 76.86 μg/ml at 5 days. Three highly efficient isolates were identified as Bacillus cereus and Bacillus subtilis by 16S rRNA analysis. Our findings demonstrate that wheat genotype and P availability distinctly shape PSB abundance in rhizospheric and endophytic niches, with the landrace supporting richer PSB communities under P stress. The study underscores the potential of harnessing PSB from landrace varieties grown under P-deficient conditions for developing biofertilizers aimed at reducing reliance on chemical phosphorus inputs.
Keywords: Wheat landrace and cultivars, phosphate fertilization, phosphate solubilizing bacteria, solubility index, 16S rRNA identification