Response Of The Coffee Plant To The Inoculation With Azospirillum Sp

T. Jiménez-Salgado, L. Vázquez-Chávez, A. Tapia-Hernández, M.A. Mascarúa-Esparza,

M. Rosas-Morales, L.E. Fuentes-Ramírez

Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Universidad Autónoma de Puebla, Apdo. Postal 1622, CP 72000, Puebla, Pue., México

The coffee plant is a crop that is cultivated in large areas of the tropics. It produces one of the greatest incomes of the non-developed countries. Competitive production of grain demands the application of large quantities of fertilizers. Nevertheless, it also produces pollution and additional impact on the finance of the farmers.

Strains of the genus Azospirillum have been used in agriculture. Several of those experiments showed plant-growth promoting activity by inoculation with Azospirillum. Beneficial effects of those strains have been reported for different crops like maize, wheat and oak. We show experiments of inoculation of coffee plantlets with different homologous Azospirillum isolates.

Samples of coffee plants from 2 to 4 years old, cv. Caturra, as well as rhizosphere were obtained from cultivated fields from Puebla and Veracruz states, México. Surface and inner tissues of coffee roots, leaves, and rhizospheric soil were inoculated in N-free semisolid NFb. After incubation of 3-5 d at 30°C, the growth was streaked in Congo Red plates and incubated for 3-5 d at the same temperature. Isolated red colonies were tested for acetylene reduction activity (ARA) and for phenoptypic identification. Four coffee Azospirillum sp. isolates were grown in N-rich NFb broth and inoculated in coffee seeds, cv. Caturra (ca. 107 CFU seed"1). The controls were non-inoculated seeds. We measured the percentage of germination at day 30, and after 180 d registered dry weight, N content and number of leaves.

The isolation frequencies oí Azospirillum ranged from 20 to 40% in samples of rhizosphere, rhizoplane and inner tissues. The samples of coffee soils were acidic or slightly acidic. Azospirillum was more abundant in slightly acidic soils. On day 30, control seeds showed germination percentage of 42% while inoculated ones increased to 67-88%. Inoculation also induced increases in biomass and N-content (Table 1), depending on the Azospirillum isolate. As has been observed in inoculation experiments with other plants, different strains can show different growth-promotion activity. We only tested cv. Caturra, but other plant genotypes could show effects different to those reported in this work.

Table 1. Effect of inoculation of four Azospirillum isolates from coffee on growth and N-content of coffee plantlets, cv. Caturraa,b.

Dry weight (g)

Number of leaves

N-content (%)

Control

0.857+ 0.1181

6.9 + 0.301

1.226+ 0.0431

CaBuap60

1.361 +0.1102

8.3 + 0.182

1.846+ 0.0562

CaBuapl20

1.617+ 0.0452'3

8.9 + 0.302

1.962+ 0.0672

CaBuap290

1.886 + 0.0823'4

9.3 + 0.262'3

2.279 +0.1023

CaBuap38

2.021 + 0.0754

10.3 + 0.413

2.867 + 0.0934

a The measures were registered 180 days after inoculation. b Mean of 10 plants + standard error

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