RizobactÃrias promotoras de crescimento e fungos micorrÃzicos arbusculares no desenvolvimento de mudas micropropagadas de bananeira




In order to study the effect of plant growth promoted bacteria (PGPB) and arbuscular mycorrhizal fungi (AMF) on development of micropropagated banana seedlings three experiments were performed. Endophytic and epiphytic bacteria were isolated from roots of six cultivars of banana and characterized regarding production of pectinase, celulase, indolacetic acid, β-1,3-glucanase and chitinase. In the first experiment, the rhizobacteria were evaluated regarding growth promotion of micropropagated seedlings of banana cv. Grand Naine, in a greenhouse, with 74 treatments of bacterization + a control, and 8 replicates. Seedlings with aproximately 10 cm were transplanted and bacterized in pots containing 1 kg of disinfested soil. In the 2nd experiment, the antagonic in vitro effect of selected PGPR against Fusarium oxysporum f. sp. cubense was evaluated. In the 3th experiment, in a greenhouse, the associated effect of PGPR and AMF on development of seedlings of banana cv. Grand Naine was studied. The experimental design was entirely at random, with seven PGPR bacterization treatments (BAN29, BAN36, BAN81, BAN82, S1, S2 and a control) Ã 3 inoculation treatments with AMF (Glomus etunicatum, Glomus clarum and a control) Ã 7 replicates. The inoculation (200 glomerospores/plant) occurred during the transplant to pots with 1.5 kg of disinfested soil. The bacterial suspensions (50 mL/plant) were adjusted to 108 UFC/mL. The control treatment without AMF and PGPR received only destilled sterilized water. For isolation of the endophytic bactaria different desinfectant substances and application times were tested. The best result was provided by 5% calcium hipoclorite during 20 minutes. Eighthy bacterial isolates, mostly epiphytic (53,7%) and Gram-positive (67,1%) were obtained. Nine isolates produced pectinase, 37 indolacetic acid and two β-1,3-glucanase. No isolate produced celulase, cianidric acid, chitinase ou solubilized phosphorus. Improvement on development of micropropagated seedlings of banana cv. Grand Naine were shown 30 days after bacterization with 40 isolates. There was an increment of up to 82% to the aerial fresh biomass and up to 263% for fresh biomass of roots associated with BAN29, BAN36, BAN81, BAN82, S1 e S2 (Experiment 1). The isolate BAN36 was able to inhibit mycelial growth of Fusarium oxysporum f. sp. cubense in Petri dishes (up to 67%) (Experiment 2). In general, the joint inoculation of PGPR and AMF did not increment growth, with interaction observed only between AMF and the isolates S1 and S2. Only in the absence of AMF the seedlings treated with BAN29, BAN36, BAN81 and BAN82 differed from the control. There was stimulus on colonization of banana roots by G. clarum when associated with BAN82. Epiphytic and endophytic bacterial isolates are able to produce, in vitro, substances with biotechnological potential to promote growth of micropropagated seedlings of banana cv. Grand Naine in order to control F. oxysporum f. sp. cubense. The interaction PGPR and AMF showed conflictant results, and we conclude that the associated effect depends on the specific isolate of each microorganism


fusarium oxysporum glomus musa aclimation amf glomus aclimatizaÃÃo musa rpcp fma pgpr ciencias biologicas fusarium oxysporum

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