216
P. T. Lacava et al.
2012; Edrisi et al. 2015), but only a few studies in Brazil have focused on the analysis
of the microbial community associated with this species (Moniruzzaman et al. 2016).
Jatropha can survive with limited nutrients and under harsh environmental conditions. Planting jatropha is also recommended for pest control, bioremediation, and
soil reclamation. Jatropha exhibits drought tolerance, rapid growth, easy propagation,
and adaptation to a wide range of environmental stress conditions. These features
make it the most popular second-generation biofuel resource (Abhilash et al. 2011).
It is not clear how jatropha adapts to extreme conditions. However, Mohanty et al.
(2017) hypothesize that its ability to adapt to environmental stresses could be due to
its endophytes (Qin et al. 2012; Madhaiyan et al. 2013).
Our research group reported the characterization of seventy-two endophytic
bacteria associated with J. curcas plants that had the potential to promote plant
growth. Of the tested isolates, 43% solubilized inorganic phosphate. These endophytic strains were identified by partial sequencing of the 16S rDNA gene, and the
most common genera were Bacillus, Citrobacter, Curtobacterium, Enterococcus,
Klebsiella, Microbacterium, Promicromonosporaceae, Sanguibacter, and Serratia
(Machado 2015). Among the endophytic genera identified and acted as potential phosphate solubilizers, Bacillus, Citrobacter, Curtobacterium, Klebsiella, and
Serratia showed a high phosphate solubilization index.
Bacillus spp. exist as endophytes that help the host plant in different ways, one
of which is supplying soluble phosphorus by solubilizing phosphorous (Kang et al.
2014; Pérez-García et al. 2011). Andrade (2012) reported six different species of
Bacillus sp. that were capable of solubilizing calcium phosphate, with solubilization indexes varying from 0.42 to 2.28 cm. Dias et al. (2009b) analyzed endophytes
isolated from strawberry, mainly Bacillus subtilis and B. megaterium, both of which
were able to solubilize phosphate. In vitro phosphate solubilization activity has also
been documented in Citrobacter sp. strains; this genus belongs to the Enterobacteriaceae family (Kämpfer 2003). In studies conducted by Reginatto (2008), a strain of
Citrobacter werkmanni with the ability to solubilize phosphate was endophytically
isolated from Vriesea friburgensis.
Recently, Machado (2019) reported on the inoculation in corn seeds of eight
endophytic bacterial strains consisted of a control (C1) containing only TSB culture
medium and the application of bacterial suspensions of EPM-2 Serratia sp. strain
(T1), EPM-4 Klebsiella sp. strain (T2), EPM-34 Curtobacterium sp. strain (T3),
EPM-41A Bacillus sp. strain (T4), EPM-54 Bacillus sp. strain (T5), EPM-63 Klebsiella sp. strain (T6), EPM-63B Citrobacter sp. strain (T7) and EPM-92 Bacillus sp.
strain (T8). Need-based irrigation was carried out, the plants were grown in a greenhouse, and Hoagland and Arnon (1950) nutrient solution was added to the plants
after 30 and 60 days of the experiment. At 30 and 60 days after sowing, the plant
vegetative parameters such as: shoot height (APA), shoot diameter (DM), shoot dry
weight (PSPA), and dry weight of the root system were examined. In the evaluations
performed at 30 and 60 days, it was observed that for the variable APA, none of the
treatments differed significantly from each other; however, the control presented a
significant difference in stem diameter from the other treatments. The DM value of
the control treatment was greater than those of the other treatments, and at the 60-day
P. T. Lacava et al.
2012; Edrisi et al. 2015), but only a few studies in Brazil have focused on the analysis
of the microbial community associated with this species (Moniruzzaman et al. 2016).
Jatropha can survive with limited nutrients and under harsh environmental conditions. Planting jatropha is also recommended for pest control, bioremediation, and
soil reclamation. Jatropha exhibits drought tolerance, rapid growth, easy propagation,
and adaptation to a wide range of environmental stress conditions. These features
make it the most popular second-generation biofuel resource (Abhilash et al. 2011).
It is not clear how jatropha adapts to extreme conditions. However, Mohanty et al.
(2017) hypothesize that its ability to adapt to environmental stresses could be due to
its endophytes (Qin et al. 2012; Madhaiyan et al. 2013).
Our research group reported the characterization of seventy-two endophytic
bacteria associated with J. curcas plants that had the potential to promote plant
growth. Of the tested isolates, 43% solubilized inorganic phosphate. These endophytic strains were identified by partial sequencing of the 16S rDNA gene, and the
most common genera were Bacillus, Citrobacter, Curtobacterium, Enterococcus,
Klebsiella, Microbacterium, Promicromonosporaceae, Sanguibacter, and Serratia
(Machado 2015). Among the endophytic genera identified and acted as potential phosphate solubilizers, Bacillus, Citrobacter, Curtobacterium, Klebsiella, and
Serratia showed a high phosphate solubilization index.
Bacillus spp. exist as endophytes that help the host plant in different ways, one
of which is supplying soluble phosphorus by solubilizing phosphorous (Kang et al.
2014; Pérez-García et al. 2011). Andrade (2012) reported six different species of
Bacillus sp. that were capable of solubilizing calcium phosphate, with solubilization indexes varying from 0.42 to 2.28 cm. Dias et al. (2009b) analyzed endophytes
isolated from strawberry, mainly Bacillus subtilis and B. megaterium, both of which
were able to solubilize phosphate. In vitro phosphate solubilization activity has also
been documented in Citrobacter sp. strains; this genus belongs to the Enterobacteriaceae family (Kämpfer 2003). In studies conducted by Reginatto (2008), a strain of
Citrobacter werkmanni with the ability to solubilize phosphate was endophytically
isolated from Vriesea friburgensis.
Recently, Machado (2019) reported on the inoculation in corn seeds of eight
endophytic bacterial strains consisted of a control (C1) containing only TSB culture
medium and the application of bacterial suspensions of EPM-2 Serratia sp. strain
(T1), EPM-4 Klebsiella sp. strain (T2), EPM-34 Curtobacterium sp. strain (T3),
EPM-41A Bacillus sp. strain (T4), EPM-54 Bacillus sp. strain (T5), EPM-63 Klebsiella sp. strain (T6), EPM-63B Citrobacter sp. strain (T7) and EPM-92 Bacillus sp.
strain (T8). Need-based irrigation was carried out, the plants were grown in a greenhouse, and Hoagland and Arnon (1950) nutrient solution was added to the plants
after 30 and 60 days of the experiment. At 30 and 60 days after sowing, the plant
vegetative parameters such as: shoot height (APA), shoot diameter (DM), shoot dry
weight (PSPA), and dry weight of the root system were examined. In the evaluations
performed at 30 and 60 days, it was observed that for the variable APA, none of the
treatments differed significantly from each other; however, the control presented a
significant difference in stem diameter from the other treatments. The DM value of
the control treatment was greater than those of the other treatments, and at the 60-day