Frankia strains of soil under Betula pendula : Behaviour in soil and in pure culture

Plant and Soil (Impact Factor: 3.24). 01/1990; 122(1):129-136. DOI: 10.1007/BF02851920

ABSTRACT The development of the nativeFrankia population was studied in a pot experiment in two types of soil; one from aBetula pendula Roth stand, with a high nodulation capacity, and one with a low nodulation capacity from aPinus sylvestris L. stand. The soils were kept at 22°C and 80% WHC. The capacity of the soils to form root nodules onAlnus incana (L.) Moench seedlings was followed over time. An increase in nodulation capacity was observed in the birch soil at pH 6 (attained
by liming). The increase was most pronounced when the soil was planted withBetula pendula seedlings. Nodulation capacity decreased in the birch soil at its original pH of 4.2, and in the pine soil (original pH 3.7),
irrespective of whether it was limed or planted.

Frankia strains were isolated fromAlnus incana root nodules, induced by soil samples from twoBetula pendula stands devoid of actinorhizal plants but showing a high nodulation capacity. The effect of various aqueous soil extracts
on the growth of the strains in propionate medium was studied. Extracts either inhibited or did not affect the growth of the
strains. No adaptation to normal soil pH and temperature conditions was found.

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    ABSTRACT: A SYBR Green based qPCR method was developed for the quantification of clusters 1 and 3 of the actinomycete Frankia in soils. Primer nifHr158 was designed to be used as reverse primer in combination with forward primer nifHf1 specifically amplifying a 191-bp fragment of the nifH gene of these Frankia. The primer combination was tested for specificity on selected pure cultures, and by comparative sequence analyses of randomly selected clones of a clone library generated with these primers from soil DNA extracts. After adjustments of DNA extraction conditions, and the determination of extraction efficiencies used for sample normalization, copy numbers of nifH genes representing Frankia of clusters 1 and 3 were quantified in different mineral soils, resulting in cell density estimates for these Frankia of up to 10(6) cells [g soil {dry weight}](-1) depending on the soil. Despite indications that the nifH gene is not a perfect target for the quantification of Frankia, the qPCR method described here provides a new tool for the quantification and thus a more complete examination of the ecology of Frankia in soils.
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    ABSTRACT: Frankia populations were analyzed in three soils devoid of actinorhizal plants but containing monocultures of birch (Betula pendula Roth), pine (Pinus sylvestris L.) or spruce (Picea abies (L.) Karsten). Bioassays using seedlings of Alnus incana as capture plants resulted in nodulation capacities of 3160±7, 2267±13, and 2747±6 nodulation units g−1 of these soils, respectively. Comparative sequence analysis of an actinomycetes-specific insertion in domain III of the 23S rRNA allowed a grouping of isolates obtained from nodules of the capture plants into three distinct groups of the Alnus host infection group. This separation was confirmed by the analysis of genomic fingerprints of the isolates generated by rep-PCR fingerprinting with the BOX primer. Genomic fingerprints also demonstrated that all isolates differed from each other. The isolates accounted for a significant proportion of the Frankia population in root nodules of the capture plants as shown by in situ hybridization with specific probes. However, only those Frankia strains isolated from soil of the birch stand via Alnus seemed to represent the total Frankia population in root nodules. Nodules induced after inoculation with soil from the pine or spruce stand also contained Frankia populations which were not isolated during this study and which could not be identified by in situ hybridization. Depending upon whether the soil originated from a birch, pine or spruce stand, different Frankia populations were found in the nodules of the capture plants. Because a nested PCR on nucleic acids extracted from these different soils did not indicate differences in the diversity of the total Frankia populations, it was concluded that Frankia populations in nodules of the capture plants represent the fraction of physiologically active, infecting frankiae in the soils rather than the total Frankia population.
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    ABSTRACT: Red alder (Alnus rubra Bong.) stands in the Pacific Northwest are the common first stage in succession following disturbance. These stands are highly productive and contribute a large amount of N to the soils as a result of their N2-fixing symbiosis with Frankia. As these alder stands age, the soils not only increase in total N, but concentrations of NO– 3 increase and pH decreases as a result of nitrification. The objective of this study was to determine how the nodulation capacity of Frankia varies as red alder stands age and if differences in nodulation capacity are related to changes in soil properties. Nodulation capacity was determined by a red alder seedling bioassay for soils from red alder stands in the Oregon coast range covering a wide range of ages. Six chronosequences were sampled, each containing a young, an intermediate, and an older alder stand. Soil total N, total C, NO– 3, NH+ 4, and pH were measured on the same soil samples. These factors as well as alder stand characteristics were compared with nodulation capacity in an attempt to identify soil characteristics typical in developing alder stands that most strongly affect nodulation capacity. Soil pH and NO– 3 concentration were highly correlated with nodulation capacity and with each other. Cluster analysis of the sites using these two variables identified two groups with distinctly different nodulation capacities. The cluster with the higher nodulation capacity was lower in NO– 3 and higher in pH than the other cluster, which included the majority of sites. There was substantial overlap in the age ranges for the two clusters and there was no significant correlation between age and nodulation capacity. Thus nodulation capacity appears to be most closely related to soil properties than to stand age.
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