Characterization of diazotrophic bacteria associated with maize: effect of plant genotype, ontogeny and nitrogen-supply

Abstract

The population size of diazotrophic bacteria naturally associated with the maize rhizosphere can be affected by biotic and environmental factors. In this work we have evaluated the effect of two genotypes of maize, with and without nitrogen fertilization, on the population dynamics and distribution of diazotrophic bacteria associated with maize plants over different plant ontogenic stages. The study was carried out in a field experiment with and without nitrogen fertilization, using two maize cultivars (Santa Helena 8447 and Santa Rosa 3063) previously selected from 32 maize cultivars for the lowest and highest response to nitrogen fertilization, respectively. Microbiological and molecular approaches were used to characterize the diazotrophic bacterial population structure. Bacterial population was assessed by the most probable number using semi-solid N-free media, and by DNA isolation from soil and plant tissue followed by amplification of nifH gene fragments using nested PCR, and by RFLP analysis using the restriction endonucleases TaqI and HaeIII. The dynamics of the diazotrophic bacterial population were affected by the ontogenic stage of the maize plants, but not by the cultivar type. Roots were the preferred site of colonization, independent of cultivar type and growth stage. During the first stage of maize growth, addition of nitrogen fertilizer negatively affected the diazotrophic bacterial population.

Desempenho Agronômico Do Milho Em Razão Do Tratamento De Sementes Comazospirillumsp. E Da Aplicação De Doses De Nitrogênio Mineral

“…no desempenho agronômico do milho são bastante variados. Roesch et al (2006) verificaram que a colonização de plantas de milho por bactérias diazotróficas foi inibida por altas doses de N durante os primeiros estádios de crescimento. Isso ocorreu porque o N mineral alterou o estado fisiológico da planta e, por consequência, a sua associação às bactérias diazotróficas.…”

“…na nutrição e produtividade do milho dependem da cultivar utilizada e das condições edafoclimáticas vigentes (Duarte et al, 2012). Influências geográficas e ambientais podem gerar associações diferentes entre bactérias diazotróficas endofíticas e plantas de milho, ocasionando resultados bastante variáveis em relação à inoculação (Roesch et al, 2006).…”

Efficiency of inoculant with Azospirillum brasilense on the growth and yield of second-harvest maize1

“…However, the results of the interaction between these bacteria and maize, in terms of agronomic potential, N fixation and growth promotion, depend on many biotic and environmental factors, including plant genotype, the microbiological community in the soil and nitrogen availability (Roesch et al 2006). According to Hungria et al (2010), it is estimated that the use of inoculants containing selected strains of Azospirillum brasilense may save approximately US$ 2 billion in chemical fertilizers, allowing reduction in transport costs, and leading to a reduction in pollution resulting from the production and use of N-fertilizers.…”

Efeito residual da adubação nitrogenada e inoculação de Azospirillum brasilense na cultura do milho

“…Entretanto, resultados da interação bactérias diazotróficas e milho em termos de potencial agronômico, fixação de nitrogênio ou promoção do crescimento, depende de muitos fatores bióticos e ambientais, tais como genótipo da planta, comunidade microbiológica do solo e disponibilidade de nitrogênio (ROESCH et al, 2006).…”