Nodulating competitiveness amongst strains of Rhizobium meliloti and R. trifolii

1974 ◽  
Vol 25 (2) ◽  
pp. 317 ◽  
Author(s):  
C Marques Pinto ◽  
PY Yao ◽  
JM Vincent
Keyword(s):  
Medicago Sativa ◽  
Trifolium Repens ◽  
Host Plants ◽  
Rhizobium Meliloti ◽  
Root Surface ◽  
Mixed Infections ◽  
Relative Speed ◽  
Nitrogen Fixing ◽  
Single Culture ◽  
The One

The relative nodulating success of strains of Rhizobium meliloti, with Medicago sativa and M. truncatula, and R. trifolii, with Trifolium repens, T. glomeratum and T. subterraneum, has been determined with inocula of paired competitors, supplied in various proportions. Host plants were raised from surface-sterilized seed, grown on agar in enclosed tubes, and populations and strain ratios were determined on the root surface as well as in the supplied inoculum. The use of heavy inoculum did not prevent all growth, and strain representation on the root surface could differ from that of the inoculum, because of either different adherence or the narrowing of extreme ratios with time. The ratios of strains obtained from nodules when related to those on the root surface yielded a 'competitive index', defined as the ratio of nodules due to each strain under conditions of equal representation on the root. In the five available cases inferior nitrogen-fixing effectiveness of a strain with a particular host was reflected in poor nodulating competitiveness, but similar differences were found in six comparisons between equally effective pairs, and with the one ineffective pair. Competitiveness did not correlate with the relative speed with which the strains produced nodules when used as a single culture or with the number of nodules they produced. Cases of mixed infections were encountered throughout the study; they generally accounted for less than 10% of the nodules typed, but in some combinations of host and strains the figure exceeded 25%.

Physiological and morphological aspects of interactions between Rhizobium meliloti and alfalfa (Medicago sativa) in association with Azospirillum brasilense

1993 ◽  
Vol 39 (6) ◽  
pp. 610-615 ◽  
Author(s):  
R. Itzigsohn ◽  
Y. Kapulnik ◽  
Y. Okon ◽  
A. Dovrat
Keyword(s):  
Medicago Sativa ◽  
Rhizobium Meliloti ◽  
Combined Treatment ◽  
Root Hairs ◽  
Background Level ◽  
Root Surface ◽  
Root Surface Area ◽  
Main Root ◽  
Nodule Number ◽  
Infection Threads

In a 50-L pot experiment with Medicago sativa grown under nonsterile conditions, a combined treatment of Azospirillum and Rhizobium was measured against soil inoculated with Rhizobium or Azospirillum alone or a control with a low background level of autochthonous rhizobia. The combined treatment significantly increased the shoot length and weight at 6 weeks and the regrowth shoot weight at 14 weeks when compared with the treatment with Rhizobium alone. In 1.5-L pots in which gnotobiotic conditions were maintained, the combined treatment led to more nodules on the main root at intermediate Rhizobium concentrations, and a greater root surface area at intermediate and high Rhizobium concentrations after 2 weeks but not after 4 weeks. In pouch-grown seedlings, plants were inoculated with either Rhizobium alone or in combination with Azospirillum or applied together with a flavonoid, luteolin (a nodulation gene inducer), or with a cytokinin, benzyl adenine. Luteolin had similar effects to those of Azospirillum in increasing the main root nodule number and the total nodule number. With Fahraeus slides, a significant increase was observed in the number of root hairs and the root diameter in the presence of Azospirillum as compared with the control and Rhizobium alone. There was no increase in the total number of infection threads; however, the combined treatment caused a significant decrease in the percentage of infected root hairs.Key words: Rhizobium, Azospirillum, Medicago, flavonoid, inoculation.

Replacing synthetic N with clovers or alfalfa in bermudagrass pastures. 1. Herbage mass and pasture carrying capacity

2017 ◽  
Vol 57 (3) ◽  
pp. 539 ◽  
Author(s):  
P. Beck ◽  
T. Hess ◽  
D. Hubbell ◽  
M. S. Gadberry ◽  
J. Jennings ◽  
...  
Keyword(s):  
Medicago Sativa ◽  
Trifolium Repens ◽  
Carrying Capacity ◽  
Nutritive Value ◽  
Cynodon Dactylon ◽  
Late Summer ◽  
Early Summer ◽  
Fertilisation Rate ◽  
Medicago Sativa L ◽  
Trifolium Repens L

The objective of this study was to evaluate the effects of including alfalfa (ALF, Medicago sativa L.) or a combination of white (Trifolium repens L.) and red (Trifolium pretense L.) clovers (CLVR) inter-seeded into bermudagrass (Cynodon dactylon L. Pers.) on herbage nutritive value compared with monocultures of bermudagrass fertilised with 0 (0N), 56 (56N), or 112 (112N) kg nitrogen (N)/ha over four grazing seasons. In autumn, at the end of the fourth year and in the spring before the fifth grazing season, alfalfa and clover plants were killed and the carryover N benefit of CLVR or ALF was compared with N fertilisation rates during the fifth year. Across years, N fertilisation rate increased herbage mass and carrying capacity linearly; whereas herbage production from CLVR and ALF swards was equivalent to 56N, were greater than 0N and less than 112N. Herbage mass in CLVR and ALF swards was greater than fertilised bermudagrass swards in the spring and did not differ from fertilised bermudagrass in the early summer. In late summer herbage accumulation of CLVR and ALF swards appeared to decrease, limiting the herbage mass in the legume pastures compared with 56N and 112N. Carrying capacity of CLVR and ALF swards was greater than fertilised bermudagrass in the spring and early summer, but did not differ from fertilised swards in the late summer. The N benefit of including legumes in bermudagrass swards can alleviate the reliance on synthetic N fertilisation with little overall effect on pasture carrying capacity.

Degradation of Nodulation Signals from Rhizobium meliloti by its Host Plants

1997 ◽  
pp. 43-46 ◽  
Author(s):  
Christian Staehelin ◽  
Maud Vanney ◽  
Fabrice Foucher ◽  
Eva Kondorosi ◽  
Michael Schultze ◽  
...  
Keyword(s):  
Host Plants ◽  
Rhizobium Meliloti

scholarly journals Colletotrichum isolates related to Anthracnose of cashew trees in Brazil: morphological and molecular description using LSU rDNA sequences

2010 ◽  
Vol 53 (4) ◽  
pp. 741-752 ◽  
Author(s):  
Ana Maria Queijeiro Lopez ◽  
John Alexander Lucas
Keyword(s):  
Mycelial Growth ◽  
Host Plants ◽  
Large Subunit ◽  
Lsu Rdna ◽  
Rdna Sequences ◽  
D2 Domain ◽  
The One ◽  
High Degree ◽  
Molecular Description ◽  
28S Ribosomal Dna

Thirty six isolates of fungi obtained from anthracnose lesions of cashew and associated host plants in Brazil, were compared by their cultural, morphological and partial sequences of the 28S ribosomal DNA characters. They showed a high degree of cultural variability. The average mycelial growth rate on all tested media ranged from 10.2-13.3 mm/day between the isolates. Most of them produced perithecia (sterile and fertile) and some produced setae (sterile and fertile). All the isolates produced acervuli with predominantly cylindrical conidia (12.4-17.7 µmX 4.8-6.0 µm in width) with round ends, which became septate on germination, and produced unlobed or slightlylobed appressoria. Comparison of the D2 domain of the large subunit (LSU) rDNA sequences with those of other defined species of Colletotrichum and Glomerella grouped 35 of the isolates with known strains of C. gloeosporioides from different hosts (> 98.9% homology). The one exception (LARS 921) was identical to G. cingulata (LARS 238) from Vigna unguiculata.

scholarly journals ABCB transporters in a leaf beetle respond to sequestered plant toxins

2020 ◽  
Vol 287 (1934) ◽  
pp. 20201311
Author(s):  
Paulina Kowalski ◽  
Michael Baum ◽  
Marcel Körten ◽  
Alexander Donath ◽  
Susanne Dobler
Keyword(s):  
Host Plants ◽  
Leaf Beetle ◽  
Protective Role ◽  
Specific Storage ◽  
Toxic Compounds ◽  
Chrysochus Auratus ◽  
Defensive Glands ◽  
The One ◽  
Uptake And Transport

Phytophagous insects can tolerate and detoxify toxic compounds present in their host plants and have evolved intricate adaptations to this end. Some insects even sequester the toxins for their defence. This necessitates specific mechanisms, especially carrier proteins that regulate uptake and transport to specific storage sites or protect sensitive tissues from noxious compounds. We identified three ATP-binding cassette subfamily B (ABCB) transporters from the transcriptome of the cardenolide-sequestering leaf beetle Chrysochus auratus and analysed their functional role in the sequestration process. These were heterologously expressed and tested for their ability to interact with various potential substrates: verapamil (standard ABCB substrate), the cardenolides digoxin (commonly used), cymarin (present in the species's host plant) and calotropin (present in the ancestral host plants). Verapamil stimulated all three ABCBs and each was activated by at least one cardenolide, however, they differed as to which they were activated by. While the expression of the most versatile transporter fits with a protective role in the blood–brain barrier, the one specific for cymarin shows an extreme abundance in the elytra, coinciding with the location of the defensive glands. Our data thus suggest a key role of ABCBs in the transport network needed for cardenolide sequestration.

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