Karakterizacija i efektivnost bakterija promotora biljnog rasta izolovanih iz rizosfere kukuruza

Abstract

Korisni mikroorganizmi ili mikroorganizmi promotori biljnog rasta (PGPM) ispoljavaju efekat na rast i razviće biljaka azotofiksacijom, mobilizacijom hraniva (N, P, Fe) u zemljištu i produkcijom fitohormona te na taj način stimulišu rast biljaka, povećavaju prinos i štite biljke od patogena. Cilj ovih istraživanja bio je da se izvrši karakterizacija bakterija izolovanih iz rizosfere kukuruza, inokulacija semena kukuruza odabranim izolatima, ispitivanje efektivnosti primene pojedinačnih i združenih kultura izolata na mikrobiološku aktivnost u rizosfernom zemljištu, kao i na početni rast i razvoj biljke, sadržaj pojedinih hranljivih elemenata u biljnom materijalu i prinos kukuruza. Korišćeno je 50 izolata iz rizosfernog zemljišta hibrida kukuruza NS 6010 gajenog na zemljištu tipa karbonatni černozem (13 izolata roda Azotobacter, 16 izolata roda Bacillus, 15 izolata roda Pseudomonas, 6 izolata roda Streptomyces). Karakterizacija izolata obuhvatila je određivanje morfoloških, fizioloških, biohemijskih i PGP osobina. Inokulacija semena kukuruza izvršena je s osam odabranih izolata primenjenih pojedinačno i u smeši i to s tri izolata azotobaktera (Azb5, Azb8, Azb13), s dva izolata bacilusa (Bac9, Bac15 ), s dva izolata pseudomonasa (Pse1, Pse5) i s jednim izolatom aktinomiceta (Act6). U ogledima su korišćeni hibridi kukuruza NS 6010 i NS 6030 selekcionisani u Odeljenju za kukuruz Instituta za ratarstvo i povrtarstvo, a efektivnost primene odabranih izolata na mikrobiološku aktivnost u rizosfernom zemljištu, kao i na biljku kukuruza, ispitana je u polukontrolisanim i poljskim uslovima. Brojnost mikroorganizama određena je metodom agarnih ploča, a dehidrogenazna aktivnost spektrofotometrijskom metodom. Uticaj izolata na klijanje semena ispitan je u laboratorijskim uslovima. Uticaj izolata na početni rast biljaka ispitan je u fazama 3. i 5-7. lista merenjem visine i suve mase nadzemnog dela biljke. Sadržaj azota, fosfora, bakra i cinka u biljnom materijalu (nadzemni deo/list) određen je u fazi 5-7. lista kukuruza za ogled u polukontrolisanim uslovima i u fazi svilanja za ogled u polju. Ukupan prinos zrna kukuruza po jedinici površine određen je preračunavanjem prinosa po svakoj elementarnoj parceli. Najbolji efekat na brojnost mikroorganizama dobijen je primenom izolata A zb5, B ac15, P se1, A ct6 i smeše i zolata.Na povećanje dehidrogenazne aktivnosti najviše je uticala primena izolata Azb5, Azb8, Bac15 i Act6. Inokulacija je imala pozitivan uticaj na klijavost, visinu i suvu masu nadzemnog dela biljke, sadržaj N, P, Zn i Cu u biljnom materijalu, kao i prinos kukuruza. Najbolji efekat na visinu i masu nadzemnog dela biljke u polukontrolisanim uslovima utvrđen je sa izolatima azotobaktera, Bac15 i Pse1, dok je u poljskim uslovima najveće povećanje ovih parametara dobijeno primenom izolata Pse5 i Act6. U proseku, najbolji efekat na prinos dobijen je primenom smeše izolata. Rezultati ovih istraživanja treba da posluže kao osnova za dalja istraživanja koja će omogućiti odabir visoko kompatibilne zajednice ispitivanih hibrida kukuruza i najefektivnijih vrsta PGPM u cilju proizvodnje mikrobiološkog preparata kojim bi se ostvario veći prinos i omogućilo održavanje i povećanje plodnosti zemljišta.

Beneficial or plant growth promoting microorganisms (PGPM) exert effect on plant growth and development through nitrogen fixation, mobilization of nutrients (N, P, Fe) in soil and production of phytohormones and thereby stimulate plant growth, increase yield and reduce pathogen infection. The aim of this study was to perform characterization of bacteria isolated from maize rhizosphere, inoculation of maize seeds with selected isolates, testing the effectiveness of single and co-inoculation on microbial activity in rhizosphere, as well as on initial growth and development of plants, content of some nutrients in plant material and yield of maize. 50 isolates from rhizosphere of maize hybrid NS 6010 grown on calcareous chernozem soil (13 isolates of the genus Azotobacter, 16 isolates of Bacillus, 15 isolates of Pseudomonas, 6 isolates of Streptomyces) were used. Characterization of isolates included determination of morphological, physiological, biochemical and PGP traits. Inoculation of maize seeds was carried out with eight selected strains applied individually and in mixture, and that with three isolates of Azotobacter (Azb5, Azb8, Azb13), two isolates of Bacillus (Bac9, Bac15), two isolates of Pseudomonas (Pse1, Pse5) and one isolate of Streptomyces (Act6). The experimental objects were maize hybrids NS 6010 and NS 6030 developed at Maize Department, Institute of Field and Vegetable Crops, and the effectiveness of selected isolates on microbial activity in rhizosphere, as well as on maize plant, was tested in semi-controlled and field conditions. The number of microorganisms was determined by agar plates method, and dehydrogenase activity by spectrophotometric method. Effect of isolates on maize seed germination was tested in the laboratory. The effect of isolates on initial plant growth was tested at 3 and 5-7 leaf stages by measuring height and dry weight of above ground plant parts. The contents of nitrogen, phosphorus, copper and zinc in plant material (above ground part/leaf) were determined at 5-7 leaf stage for experiment in semi-controlled conditions and at silking stage for field trial. Thetotal grain yield per unit area is determined by recalculating yield for each elementary plot. The best effect on the number of microorganisms was obtained by applying Azb5, Bac15, Pse1, Act6 and mixtures of isolates. The largest increase in dehydrogenase activity was achieved with isolates Azb5, Azb8, Bac15 and Act6. Inoculation had a positive impact on germination, height and dry weight of above ground part of the plant, the content of N, P , Z n and C u i n p lant material, as well as the yield of maize. The best effect on the height and weight of above ground part of the plant in semi-controlled conditions was achieved with isolates of azotobacters, Bac15 and Pse1, while in field conditions the largest increase in these parameters was obtained with isolates Pse5 and Act6. On average, the best effect on yield was obtained by using a mixture of isolates. The results of this study should be the basis for further research which would allow the selection of highly compatible community of maize hybrids and the most effective strains of PGPM and be used in the production of microbial preparations in order to achieve higher yields and facilitate the maintenance and increase fertility of soil.