Endophytic Bacteria In Induced Root Nodules On Eggplant And Tomato

G. Yongjun

G-Laboratory, Beijing Liuhe Newstar Biological Technology Co. Ltd.

Beijing, 100832 China

Through optical microscopes, transmitting electron microscopes and scanning electron microscopes, the ultrastructure of and endophytic bacteria in artificially-induced nodules on the roots of eggplant (Solarium melongena L.) and tomato (Lycopersicon esculentum Mill.), plants were observed and studied. The results show that a large number of nodules formed on the root system due to intrusion of autogenous azotobacters. Within the root nodule cells, two strains of azotobacters were found. One was bacillus-brevis-type azotobacter of genus Berjerinckia Derx 1950 and the other Azotobacter chroococcum Beijerinck 1901. The latter was found in three different development forms, i.e. thallus, sporangium and sporangiospores, in the root nodule. They and their host plant formed a new type of symbiosis, which is quite rare in nature. This new type of symbiotic relationship between them will be elaborated in this paper.

ENDOPHYTIC ASSOCIATION BETWEEN RHIZOBIUMLEGUMINOSARUM BY. VICIAE AND ROOTS OF NONLEGUME CROPS

N.Z. Lupwayi1, G.W. Clayton1, Y.O. Biederbeck2, W.A. Rice1

Agriculture and Agri-Food Canada, Lacombe-Beaverlodge Research Centre, AB, Canada 2Agriculture and Agri-Food Canada, SPARC, Swift Current, SK, Canada

1. Introduction

Endophytic rhizobia have been observed in nonlegumes and it is speculated that they improve the nutrition of these crops. The objective of this work was to investigate the effects of pea-based crop rotations on endophytic rhizobia and other bacteria in barley, wheat and canola roots.

2. Procedures

Barley, wheat and canola were each grown (a) continuously, (b) following uninoculated peas, or (c) following inoculated peas. Plants were sampled at flag-leaf stage (barley and wheat) or flowering stage (canola), and roots were surface-sterilized and macerated to extract endophytic bacteria. The endophytes were plate-counted on nutrient agar (NA), and their diversity was evaluated using the BIOLOG method. Endophytic rhizobia in the macerate were enumerated by the most probable number (MPN) method. At crop maturity, grain yields and N were measured.

3. Results and Discussion

Table 1. Effects of previous crop on populations of wheat endophytic bacteria and yield.

Previous crop

Endophytic rhizobia

Endophytic bacteria

Diversity of bacteria

Wheat grain yield

Wheat grain N

Log (cells

g"1 soil)

H'

Mg ha"1

kg ha"1

Wheat

0.69b

6.64a

2.72b

1.03b

19.5b

Uninoculated peas

3.27a

7.00a

2.83b

1.70a

34.0a

Inoculated peas

2.00c

6.49a

3.12a

1.64a

32.7a

Wheat results are presented (Table 1). Endophytic rhizobium populations were in the order: crop following uninoculated peas > crop following inoculated peas > continuously-grown crop. This means either (a) that indigenous rhizobia, stimulated by growing a legume crop, are better endophytic colonizers than inoculant rhizobia, or (b) that the inoculant rhizobium strain used in this experiment was a poor endophytic colonizer. The diversity, but not the populations, of all bacteria was greatest after inoculated peas. Grain yields and N uptake of crops grown after peas were significantly greater than yields of continuously-grown crops. Yield was correlated more with populations of endophytic rhizobia than with those of all endophytic bacteria, implying that endophytic rhizobia probably contribute to the rotational benefits of legumes to nonlegumes.

ACETOBACTER DIAZOTROPHICUS AND HERBASPIRILLUM SEROPEDICEAE NITROGENASE ACTIVITY IN THE SANDY-LOAM SOIL UNDER ITALIAN RYEGRASS (LOLIUMMULTIFLORUM LAM.) CULTIVATION

A. Sawicka, J. Klama

Department of Agricultural Microbiology, Agricultural University of Poznan, Wolynska 35, 60-635 Poznan, Poland

1. Introduction

Acetobacter diazotrophicus and Herbaspirillum seropediceae were discovered in crop plants characteristic for tropical climate such as sugarcane, sorghum, sweet potatoes and grasses. Until now, very little is known about the occurrence of these bacteria in the climate of the temperate zone. Therefore, the objective of this experiment was to recognize possibilities of the influence of the inoculation of Italian ryegrass with Acetobacter and Herbaspirillum on N2 fixation activity.

2. Material and Methods

Italian ryegrass (Lolium multiflorum Lam.) cultivar Kroto was cultivated in an experimental box with loamy sand soil in a cold greenhouse. Grass seeds were inoculated with Acetobacter diazotrophicus and Herbaspirillum seropediceae directly before sowing. Non-inoculated seeds were treated as control. Nitrogenase activity in the soil under grass was measured after 3, 7, 9 and 12 weeks after sowing date using the acetylene to ethylene reduction method (ARA).

3. Results

The activity of N2 fixation increased up to the 9th week of grass development (Table 1).

Table 1. Nitrogenase activity in the soil under Italian rye grass.

C2H4 (nanomoles h"1 plant"1)

Experimental combinations

After 3 weeks from sowing

After 7 weeks from sowing

After 9 weeks from sowing

After 12 weeks from sowing

Grass without inoculation (control)

0.8

7.2

9.3

3.5

Grass inoculated with Acetobacter

1.8

11.5

18.6

7.1

Grass inoculated with Herbaspirillum

1.2

7.4

10.2

4.3

Grass inoculated with Acetobacter and Herbaspirillum

1.5

9.6

14.7

5.6

The highest nitrogenase activity was observed 7 and 9 weeks after sowing of inoculated seeds irrespective of the bacteria used for inoculation. The best effect was recorded when grass seeds were inoculated with Acetobacter.

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