Rizobactérias - ARTIGO

Rizobactérias - ARTIGO

(Parte 1 de 3)

International Research Journal of Microbiology Vol. 2(2) p. 070-078 February 2011 Available online@ http://www.interesjournals.org/IRJM Copyright ©2011 International Research Journals

Full Length Research

Isolation and selection of growth-promoting bacteria of the genus Bacillus and its effect on two varieties of lettuce (Lactuca sativa L.)

J.T. P. Ferreira1 , T.M.C. Santos2*

, L. S. Albuquerque3

, J.V.Santos,4 J.A. Cardoso Filho2 . C. E.

Ramalho Neto2 .

1Universidade Federal Rural de Pernambuco - Pos-Graduate Program in Soil Science 2Universidade Federal de Alagoas – UFAL 3Agronomist - Universidade Federal de Alagoas – UFAL 4Fellow Industrial Technology Development of CNPq -Universidade Federal de Lavras

Accepted 05 January, 2011

The objective of this study was to assess rhizobacteria isolates of the genus Bacillus and check which are more promising for the production of seedlings of two varieties of lettuce (Lactuca sativa L.). Seeds of two varieties of lettuce (Babá de Verão Manteiga (smooth) and Monica SF 31 SF 31 (crisp) were inoculated in styrofoam trays where each cell received substrate with 5 ml of bacterial suspension containing Bacillus spp. adjusted A580 = 0.7, and taken to a greenhouse for 25 days as being variables: weight of dry matter of aerial part (WDMAP), root

(WDMR), total (WDMT), leaf area (LA), length leaf (L), length root (LR) and number of leaves (NL). For Babá de Verão Manteiga variety the isolated 8 highlighted variables WDMAP, WDMR and WDMT and increase index (I) 62.3% 38.5% 59.1% respectively while for what LA and L and the isolate 7 showed better results with I of 73.3% and 28.4%. The variety Monica SF 31 the best results for WDMAP and L were obtained with the strain 1 having I of 31.0% and 29.1% respectively, while for WDMR and WDMT, isolate 4 showed I 6.7% and 3.7% respectively. To variable LR the isolate 6 highlighted for both varieties.

Keywords: Lactuca sativa L., rhizobacteria, Bacillus spp., PGPR

Lettuce (Lactucca sativa), a leafy vegetable most commonly consumed among Brazilians, is sensitive to the adverse conditions of temperature, humidity and rain, requiring special attention regarding the control of pests and diseases, polluting the environment, enhancing the product and can harm the health of consumers.

Plant growth is influenced by the interaction of these with the environment to the root system. This environment is represented by the soil or the planting substrate. The microflora interacts with the roots and plays an important role in the growth and survival of plants. The bacteria that promote plant growth represent an important segment of these microorganisms by promoting growth, increasing productivity and health of plants (Bettiol, 1995).

*Corresponding author’s email: tmcs@ceca.ufal.br

Among the most studied groups of bacteria and of great potential for use in agriculture are plant growth promoting rhizobacteria (PGPR), representing a diverse subset of bacteria that colonize the roots. The study of these microorganisms comes with prominence in recent years. Due to great demand for technology 'clean', ie the viability of sustainable agriculture can be expected that in future, a greater percentage of these bacteria is used in food production.

The rhizobacteria are bacteria that inhabit the rhizosphere, ie the region that is influenced by the roots. These bacteria can be beneficial, for example, PGPR, neutral or pathogenic to plants. Among the key PGPR include: Pseudomonas fluorescent spp., Bacillus spp. Azospirillum spp. and Azotobacter spp (Gomes et al., 2003; Silveira et al., 2004; Coelho, 2006).

The PGPR can increase plant growth by promoting the mineralization of nutrients, the mineral phosphate solubilization, production of growth hormones like auxin

Ferreira et al. 071

Table 1. Characterization of isolates of Bacillus spp

Isolates Origin

1, 2, 3 Lettuce roots gathered in the garden of the School

Agrotécnica Federal de Satuba in the municipality of Satuba - AL.

4,5,6 Lettuce roots collected in growing organic business in the city of Arapiraca - AL.

7, 8 Collection of plant pathology laboratory UFAL.

and gibberellin (Asghar et al., 2002; Joo et al., 2004). Moreover, PGPR are important biological control agents because they can eliminate pathogens from the rhizosphere, the production of beta-1, 3-glucanase, chitinases, antibiotics, hydrogen cyanide, and siderophores, which are composed of low molecular weight iron chelators produced by most bacteria under limiting conditions of this element. (Owen and Zdor, 2001; Pidello, 2003; Coelho, 2006.) Can also act as bioremediation of contaminated areas by degrade xenobiotics.

The inoculant production of low cost rhizobacteria promote plant growth (PGPR) is an alternative to reduce the use of pesticides and chemicals, which, if used wrongly, can reach the water table and contaminate water resources. Furthermore, the use of such inoculants can increase agricultural production, making the product more competitive and differentiated as well as reduce the costs to the producer, the less need for inputs.

Within this context, the objective of this study was to isolate rhizobacteria of the genus Bacillus and check which rhizobacteria isolates were more promising in the production of lettuce.

The experiments were conducted at the Federal University of Alagoas (UFAL) in the laboratory of Agricultural Microbiology and Experimental Field in the city Rio Largo situated in the geographic coordinates 9°27'57,3” S and 35°49'57,4” W.

Roots and stems of healthy lettuce were collected in commercial crops of vegetables. To make the insulation used the method of the World Health Organization (World Health Organization, 1985). One gram of soil and macerated roots of each sample were placed in sterile tubes with 10 ml of saline and agitated in vortex for 2 minutes. Then 1.5 ml were transferred to sterile tubes and subjected to heating for 12 minutes at 80° C and 5 minutes on ice.

The samples were then diluted 1000 times in sterile saline solution, seeded in Petri dishes containing nutrient agar, spread with the aid of handle Drigalski and incubated at 30° C. After 48 hours logged to an examination of the colonies and isolated to those typical of the bacilli with absence of pigmentation, wavy edges, opaque and positive reaction for amylolyse were isolated.

The seedlings were grown in sterilized by autoclaving substrate at 121°C for an hour, contained in tray polystyrene, seeds of cultivars Babá de Verão Manteiga (smooth) and Monica SF 31 (crisp) were bacterized, depositing aliquots of 5ml of a tuned suspension with a colorimeter at 580 nm, control consisted of a solution of 0.1 M. of MgSO4. After 25 days the following variables were analyzed: weight of dry matter of aerial part (WDMAP), root (WDMR), total (WDMT), leaf area (LA), length leaf (L), length root (LR) and number of leaves (NL). It was used the formula I (%) = [(bacterized-control) / control] X 100, to verify the increase index (I).

Leaves and stems of lettuce plants were placed in an oven at 65°

C until they had constant weight and weighed in the balance of precision WDMAP determined. Performing the same procedure was determined WDMR and the sum of two-and results WDMAP and WDMR was observed the WDMT.

LA was determined woodpecker "weighing method of discs" of

Blackman and Wilson (1951), cited by Luchesi (1987). Is to perforate the sheet with a punch of known area, where this part is placed, along with the rest of the sheet that was perforated to dry in oven at 600° C until constant weight present to be weighed in the balance of precision. Is subsequently used the formula: LA = (known area of perforated sheet X part of the remaining leaf weight) / weight of the area known part of the perforated leaf.

L was established by choosing the two largest leaves of each plant and with the aid of a ruler held measurements. The roots were washed carefully to avoid loss of roots, and with the aid of a ruler held the measurements for the LR.

The design was a randomized block design with four replications and experimental units consisted of 16 plants. Data were submitted to analysis of variance and test F (5% of probability) and averages compared by Scott Knott at 5% probability. The isolates are caracterized in of Table 1.

The eight isolates were obtained from roots of lettuce from the garden School Agrotecnica Federal Satuba, city of Satuba - AL (Figure 1) and commercial organic farming in the city of Arapiraca - AL (Figure 2) showed rod- shaped cells and clusters of cells in pairs or chains characteristic of bacteria of the genus Bacillus.

For data on weight of dry matter of aerial part

(WDMAP) is the F test at 1% probability detected significant differences between treatments. There were significant differences at the level of 1% in the F test between the two varieties of lettuce (Lactuca sativa L.) among isolates of Bacillus spp. and the interaction (Variety x Bacteria).

The values ranged from 0.053 g WDMAP 0.086 g for variety Babá de Verão Manteiga and the mean equal to 0.073 g while the variety Monica SF 31 values ranged from 0.050 g to 0.076 g with an average 0.061. Figure 3 presents the data WDMAP. Isolates of Bacillus spp. 1, 2, 5, 6, 7 and 8 did not differ statistically and

072 Int. Res. J. Microbiol.

Figure 1. Isolates of Bacillus spp. obtained from the roots of lettuce Horta School Agrotécnica Federal Satuba.

Figure 2. Production of seedlings of two varieties of lettuce in a greenhouse unit of agricultural sciences academic center ((A) BABÁ SUMMER BUTTER (smooth) (B) MÔNICA SF 31 (crisp)).

provided the best results for a variety Babá de Verão Manteiga with an I averaged 47.2%, however, the 8 isolate presented the highest result, with I from 62.3% to WDMAP compared to control. The isolates 3 and 4 differed from isolates 1, 2, 5, 6, 7 and 8, WDMAP demonstrating the variety below for Babá de Verão Manteiga. For variety Monica SF 31 (crisp) isolates of Bacillus spp. 1, 3 and 4 did not differ statistically and the best results on average a I of 24.1% with isolate 1 showed the highest result, increasing 31.0% over the WDMAP the control.

Isolates 2, 5, 6, 7 and 8 differ from the isolated 1, 3 and 4, with lower results for the variety Monica SF 31. Isolates 2, 5, 6 and 7 were lower than the control on average 8.6% for WDMAP.

The isolated 1, not statistically different in the two varieties of lettuce showing good results in an average I of 36.2% for both varieties in comparison with the controls, showing an interaction with this isolate varieties. It was also noted that the variety Babá de Verão Manteiga differed significantly from the variety Monica SF 31, being more than Monica SF 31, a difference of 19.7% I of WDMAP.

For WDMR significant differences were detected at 1% probability among the varieties of lettuce and among isolates of Bacillus spp. in relation to WDMR. For the

significance level of 5% by F test

interaction (Variety x bacteria) were detected at In figure 4 are the data WDMR, where isolates of

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