Bacillus spp. como promotores de crescimento na cultura do algodão.
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2018-03-09
Autores
Diaz, Paola Andrea Escobar
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Universidade Estadual Paulista (Unesp)
Resumo
O uso contínuo de fertilizantes minerais na agricultura promove o excesso de nutrientes como fósforo, nitrogênio e potássio o que ocasiona danos ao ecossistema e leva à alteração da microbiota do solo. Além disso, existe uma baixa eficiência das plantas em absorver e utilizar esses nutrientes o que gera perdas da adubação mineral. Neste sentido o uso de bactérias promotoras de crescimento de plantas (BPCP) é uma alternativa promissora para melhorar a eficiência das plantas na utilização dos fertilizantes minerais. O presente trabalho teve por objetivo avaliar o potencial de dez isolados Bacillus (oito isolados de Bacillus subtilis, um isolado de Bacillus velezensis e um isolado de Bacillus amyloliquefaciens) quanto à sua capacidade de promoção de crescimento na cultura de algodão em condições de vaso em casa de vegetação. O experimento foi realizado em delineamento inteiramente casualizado com 11 tratamentos e cinco repetições. Os parâmetros avaliados foram altura da planta, massa seca da parte aérea e raiz, teores de clorofila nas folhas, nitrogênio e fósforo na planta e no solo. A massa seca total (parte aérea e raiz) foi maior nos isolados 248 e 290 (B. subtilis), e maiores valores de altura das plantas foram obtidos para o isolado 248. O teor de clorofila nas folhas foi superior nas plantas inoculadas com o isolado 290, indicando que o mesmo foi capaz de aumentar a atividade fotossintética das plantas de algodão. Os teores de nitrogênio na parte aérea e na raiz foram superiores nos tratamentos com os isolados 248 e 290, o que indica que houve estabelecimento dessas bactérias na rizosfera melhorando a disponibilidade e absorção de nitrogênio pela planta. O teor de fosforo na raiz foi maior em plantas que receberam o isolado 001 (B. amyloliquefaciens) o que indica que esse isolado favorece a absorção de fósforo pela planta. O isolado 248 apresentou maior quantidade de fósforo solúvel disponível no solo o que demostra que B. subtilis atua positivamente na solubilização do fósforo. A análise molecular do DNA ribossomal 16S de isolados obtidos do reisolamento a partir do solo e raiz das plantas do algodão confirmam a identidade das linhagens utilizadas. Finalmente, os isolados 248 e 290 de B. subtilis têm a capacidade de aumentar os teores de clorofila e nitrogênio nas plantas, altura e matéria seca, e também solubilizam fósforo, o que os torna agentes potencias para uso como bioinoculantes nas plantas de algodão.
The continuous use of mineral fertilizers in agriculture promotes the excess of nutrients as phosphorus, nitrogen and potassium in the ecosystems which causes damages and leads to the instability of the soil microbiota. Moreover, a low efficiency of the plants to absorb and use these nutrients causes losses of the mineral fertilization, but the use of plant growth promoting bacteria (PGPB) is a promising alternative to improve plant efficiency in the use of mineral fertilizers implying in the reduction of its application on the crops. This work aimed to evaluate the potential of ten Bacillus strains (eight of B. subtilis, one of B. velezensis and one of B. amyloliquefaciens) about their capacity to promote growth of cotton seedlings on greenhouse conditions. The experiment was carried out in a completely randomized design with 11 treatments and five replicates. The parameters evaluated were plant height, dry matter of aerial part and root, chlorophyll content in leaves, nitrogen and phosphorus in the plant and soil. The total dry matter (aerial part and root) was higher to the isolates 248 and 290 of B. subtilis, and higher values of plant height were obtained for the isolate 248. The chlorophyll content in leaves was higher in plants inoculated with the isolate 290 what indicates that this isolate was able to increase the photosynthetic activity of cotton seedlings. The nitrogen content in the aerial part and roots was higher at the treatments with the isolates 248 and 290 indicating that the bacteria were established in the rhizosphere improving the nitrogen availability and absorption by the plant. The phosphorus content in the roots was higher in seedlings treated with the isolate 001 of B. amyloliquefaciens, what demonstrates that this isolate favors its uptake by the plant. The isolate 248 provided the highest amount of soluble phosphorus available in the soil, which shows that B. subtilis acts positively on phosphorus solubilization. The molecular analysis of 16S Ribosomal DNA from isolates obtained from reisolation from the soil and roots of cotton seedlings confirms the identity of the strains used at the experiment. Finally, isolates 248 and 290 of B. subtilis are able to increase nitrogen and chlorophyll contents in the plants, high and dry matter, and also solubilize phosphorus, which make them potential agents for use as bioinoculants in cotton plants.
The continuous use of mineral fertilizers in agriculture promotes the excess of nutrients as phosphorus, nitrogen and potassium in the ecosystems which causes damages and leads to the instability of the soil microbiota. Moreover, a low efficiency of the plants to absorb and use these nutrients causes losses of the mineral fertilization, but the use of plant growth promoting bacteria (PGPB) is a promising alternative to improve plant efficiency in the use of mineral fertilizers implying in the reduction of its application on the crops. This work aimed to evaluate the potential of ten Bacillus strains (eight of B. subtilis, one of B. velezensis and one of B. amyloliquefaciens) about their capacity to promote growth of cotton seedlings on greenhouse conditions. The experiment was carried out in a completely randomized design with 11 treatments and five replicates. The parameters evaluated were plant height, dry matter of aerial part and root, chlorophyll content in leaves, nitrogen and phosphorus in the plant and soil. The total dry matter (aerial part and root) was higher to the isolates 248 and 290 of B. subtilis, and higher values of plant height were obtained for the isolate 248. The chlorophyll content in leaves was higher in plants inoculated with the isolate 290 what indicates that this isolate was able to increase the photosynthetic activity of cotton seedlings. The nitrogen content in the aerial part and roots was higher at the treatments with the isolates 248 and 290 indicating that the bacteria were established in the rhizosphere improving the nitrogen availability and absorption by the plant. The phosphorus content in the roots was higher in seedlings treated with the isolate 001 of B. amyloliquefaciens, what demonstrates that this isolate favors its uptake by the plant. The isolate 248 provided the highest amount of soluble phosphorus available in the soil, which shows that B. subtilis acts positively on phosphorus solubilization. The molecular analysis of 16S Ribosomal DNA from isolates obtained from reisolation from the soil and roots of cotton seedlings confirms the identity of the strains used at the experiment. Finally, isolates 248 and 290 of B. subtilis are able to increase nitrogen and chlorophyll contents in the plants, high and dry matter, and also solubilize phosphorus, which make them potential agents for use as bioinoculants in cotton plants.
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Palavras-chave
BPCP, Fixação de nitrogênio, Solubilização de fósforo, Teor de Clorofila, Massa Seca, Altura, Eficiência de adubação, nitrogen fixation, phosphorus solubilization, chlorophyll content, shoot and root dry matter, height, fertilization efficiency