The effect of PGPR strains on microbial abundance in maize rhizosphere in field conditions

Abstract

Plant growth promoting rhizobacteria (PGPR) represent a wide variety of bacteria inhabiting the root surface and root vicinity. They are directly or indirectly involved in promoting plant growth and development via production and secretion of various regulatory compounds in the rhizosphere. PGPR are generally beneficial to a wide range of crops including maize. The main objective of this study was to determine the effect of PGPR strains on the microbial abundance in maize rhizosphere. The trial was conducted at Rimski Šančevi experimental field of Institute of Field and Vegetable Crops in Novi Sad, Serbia. The trial included five maize hybrids (NS 3014, NS 4015, NS 5043, NS 6010 and NS 6030) developed at the Institute and three treatments with microorganisms. Non-inoculated treatment was control. Inoculation was performed with Bacillus Q7, Pseudomonas PS2 and their mixture with Azotobacter chroococcum (Q7 + PS2 + AC). Application method was incorporation immediately before planting with liquid culture of strains (density 109 CFU/ml). It was observed that the certain treatment with rhizobacteria increased the number of all three studied microbial groups in the rhizosphere of the same hybrid. The best effect on the number of microorganisms in the rhizosphere of NS 6010 was achieved with Q7 + PS2 + AC, in NS 5043 with Q7 and with PS2 in NS 4015. The results obtained in this study indicate the importance of PGPR in crop production, which requires a constant expansion of knowledge about the mutual interactions of plants and microorganisms.

Rizobakterije koje poboljšavaju rast biljaka (PGPR) predstavljaju širok spektar bakterija koje naseljavaju prostor oko/na površini korena. Direktno ili indirektno su uključene u ubrzanje rasta i razvoja biljaka putem proizvodnje i lučenja različitih regulatornih materija u rizosferu. PGPR su generalno korisne kod širokog spektra useva uključujući kukuruz. Osnovni cilj ovog istraživanja bio je ispitivanje efekta PGPR sojeva na zastupljenost mikroorganizama u rizosferi. Ogled je postavljen na eksperimentalnoj parceli Rimski šančevi Instituta za ratarstvo i povrtarstvo u Novom Sadu i uključivao je pet hibrida kukuruza poreklom iz Instituta (NS 3014, NS 4015, NS 5043, NS 6010 i NS 6030); kontrolu (bez inokulacije) i tri tretmana bakterijama koje poboljšavaju rast biljaka. Inokulacija je izvršena sa Pseudomonas PS2, Bacillus Q7 i njihovom mešavinom sa Azotobacter chroococcum (Q7 + PS2 + AC). Sojevi su primenjeni inkorporacijom tečne kulture (gustine 109 CFU/ml) neposredno pre setve. Rezultati su pokazali da kod određenog hibrida određeni tretman rizobakterijama povoljno utiče na brojnost kod sve tri analizirane grupe mikroorganizama. Najpovoljniji efekat na broj mikroorganizama u rizosferi hibrida NS 6010 postignut je primenom tretmana Q7 + PS2 + AC, kod NS 5043 primenom Q7, a kod NS 4015 primenom PS2.