Resource partitioning in the rhizosphere by inoculated Bacillus spp. towards growth stimulation of wheat and suppression of wild oat (Avena fatua L.) weed

Abstract

Common wheat (Triticum aestivum L.) is one of the most important agricultural crop, which provides direct source of food for humans. Besides abiotic stresses, weeds pose a significant challenge to successful crop production. Avena fatua (wild oat) is one of the most common damaging grass weed, which causes 17-62% losses in yield of winter wheat. Excessive use of herbicides to control wild oat has resulted in serious environmental and human health hazards. Therefore, biological control of weeds is required to cope up with the increasing food demand and to attain self-sustainability. In this study, eighty eight rhizobacterial isolates were isolated from rhizosphere soil samples collected from Rewari and Hisar districts. After screening of the isolates, only thirty isolates showed in vitro antagonistic and herbicidal activities. The selected antagonistic isolates were further tested for production of IAA and ALA, and utilization of ACC. Bacterial isolates BWA18 and RWA52 produced 53.80 and 19.18 ug ml^-1 IAA, respectively and high ALA production was shown by isolates HCA3 and RCA3. Five isolates i.e., BWA20, BWA23, BWA29, BWA38 and RCA3 showed significant ACC utilization. Inoculation of selected bacterial isolates BWA18, RWA69 and SYB101 showed significant increase in root dry weight (RDW) and shoot dry weight (SDW) of wheat plants under pot house conditions, and decreased RDW and SDW of A. fatua weed as compared to RDF-amended uninoculated soil at 25 DAS (days after sowing). Bacterial isolates RWA69 and SYB101 caused significant increase in RDW and SDW of wheat growth at 50 DAS, whereas their inoculation decreased RDW and SDW of A. fatua. Thus, seed bacterization with bacterial isolates RWA52, RWA69 and SYB101 caused significant increase in RDW and SDW of wheat, whereas their inoculation caused significant decrease in RDW and SDW of A. fatua. The best performing bacterial isolates RWA52 and RWA69 were identified as Bacillus siamensis and Bacillus endophyticus using 16S rRNA analysis. The promising rhizobacterial isolates could further be tested for the bioherbicidal activity and plant growth promotion effects under field conditions before their use as bioherbicides.

Keywords: Avena fatua; Bacillus sp.; Bioherbicides; Resource partitioning; Rhizosphere bacteria; Wheat.