scholarly journals Study of the genetic organization of the strain Rhizobium leguminosarum bv. trifolii forming a symbiosis with clover Trifolium ambiguum

2020 ◽  
Author(s):  
T. S. Aksenova ◽  
O. P. Onishchuk ◽  
O. N. Kurchak ◽  
E. E. Andronov ◽  
N. A. Provorov
Keyword(s):  
Host Specificity ◽  
Rhizobium Leguminosarum ◽  
Trifolium Ambiguum ◽  
Genetic Organization

R. leguminosarum bv. trifolii strains are characterized by narrow host specificity. We have identified a strain that forms nodules on several types of clover and studied the genetic organization of its symbiotic region.

scholarly journals Genetic organization of the hydrogen uptake (hup) cluster from Rhizobium leguminosarum.

1990 ◽  
Vol 172 (3) ◽  
pp. 1647-1655 ◽  
Author(s):  
A Leyva ◽  
J M Palacios ◽  
J Murillo ◽  
T Ruiz-Argüeso
Keyword(s):  
Rhizobium Leguminosarum ◽  
Hydrogen Uptake ◽  
Genetic Organization

scholarly journals Lysogeny in Rhizobium Leguminosarum and Rh. Trifolii

1963 ◽  
Vol 16 (3) ◽  
pp. 597 ◽  
Author(s):  
E A Schwinghamer ◽  
DJ Reinrardt
Keyword(s):  
Host Range ◽  
Host Specificity ◽  
Ultraviolet Light ◽  
Rhizobium Leguminosarum ◽  
Clear Plaque ◽  
Rhizobial Species ◽  
Lysogenic Conversion ◽  
Light Inducibility

Seven lysogenic strains-three of Rh. legumino8urum and four of Rh. trifoliiwere identified among a total of 54 strains from these two species and Rh. phaseoli. The Rh.leguminosarum strains may be multiply lysogenic; two of them also produce lethal agents resembling bacteriocins in their effect. Lysogeny was confumed by standard criteria of ultraviolet light inducibility, self.immunity, and reductive ability. Lysogenic conversion involving symbiotic characteristics was not observed. A minimum of six different temperate phages and two clear-plaque-forming variant phages were identified. The host range includes strains of the above three rhizobial species, but not of Rh. melilotii. Variation in host specificity of some phages following host passage is under investigation.

scholarly journals Competitive Nodulation Blocking of cv. Afghanistan Pea Is Related to High Levels of Nodulation Factors Made by Some Strains of Rhizobium leguminosarum bv. viciae

2002 ◽  
Vol 15 (1) ◽  
pp. 60-68 ◽  
Author(s):  
Bridget Hogg ◽  
Andrea E. Davies ◽  
Karen E. Wilson ◽  
Ton Bisseling ◽  
J. Allan Downie
Keyword(s):  
Gene Expression ◽  
Host Specificity ◽  
Rhizobium Leguminosarum ◽  
Gene Region ◽  
Nod Factors ◽  
Nod Factor ◽  
Present Evidence ◽  
Factor Production ◽  
Nodulation Factors ◽  
Nod Gene Expression

Cultivar Afghanistan peas are resistant to nodulation by many strains of Rhizobium leguminosarum bv. viciae but are nodulated by strain TOM, which carries the host specificity gene nodX. Some strains that lack nodX can inhibit nodulation of cv. Afghanistan by strain TOM. We present evidence that this “competitive nodulation-blocking” (Cnb) phenotype may result from high levels of Nod factors inhibiting nodulation of cv. Afghanistan peas. The TOM nod gene region (including nodX) is cloned on pIJ1095, and strains (including TOM itself) carrying pIJ1095 nodulate cv. Afghanistan peas very poorly but can nodulate other varieties normally. The presence of pIJ1095, which causes increased levels of Nod factor production, correlates with Cnb. Nodulation of cv. Afghanistan by TOM is also inhibited by a cloned nodD gene that increases nod gene expression and Nod factor production. Nodulation of cv. Afghanistan can be stimulated if nodD on pIJ1095 is mutated, thus severely reducing the level of Nod factor produced. Repression of nod gene expression by nolR eliminates the Cnb phenotype and can stimulate nodulation of cv. Afghanistan. Addition of Nod factors to cv. Afghanistan roots strongly inhibits nodulation. The Cnb+ strains and added Nod factors inhibit infection thread initiation by strain TOM. The sym2A allele determines resistance of cv. Afghanistan to nodulation by strains of R. leguminosarum bv. viciae lacking nodX. We tested whether sym2A is involved in Cnb by using a pea line carrying the sym2A region introgressed from cv. Afghanistan; nodulation in the introgressed line was inhibited by Cnb+ strains. Therefore, the sym2A region has an effect on Cnb, although another locus (or loci) may contribute to the stronger Cnb seen in cv. Afghanistan.

Genetic variation for rate of establishment in caucasian clover

1998 ◽  
pp. 213-217
Author(s):  
K.H. Widdup ◽  
T.L. Knight ◽  
C.J. Waters
Keyword(s):  
Genetic Variation ◽  
Root Growth ◽  
Seedling Growth ◽  
White Clover ◽  
Seedling Emergence ◽  
Red Clover ◽  
Dry Weight ◽  
Cool Season ◽  
Trifolium Ambiguum ◽  
Root Dry Weight

Slow establishment of caucasian clover (Trifolium ambiguum L.) is hindering the use of this legume in pasture mixtures. Improved genetic material is one strategy of correcting the problem. Newly harvested seed of hexaploid caucasian clover germplasm covering a range of origins, together with white and red clover and lucerne, were sown in 1 m rows in a Wakanui soil at Lincoln in November 1995. After 21 days, the caucasian clover material as a group had similar numbers of emerged seedlings as white clover and lucerne, but was inferior to red clover. There was wide variation among caucasian clover lines (48-70% seedling emergence), with the cool-season selection from cv. Monaro ranked the highest. Recurrent selection at low temperatures could be used to select material with improved rates of seedling emergence. Red clover and lucerne seedlings produced significantly greater shoot and root dry weight than caucasian and white clover seedlings. Initially, caucasian clover seedlings partitioned 1:1 shoot to root dry weight compared with 3:1 for white clover. After 2 months, caucasian clover seedlings had similar shoot growth but 3 times the root growth of white clover. Between 2 and 5 months, caucasian clover partitioned more to root and rhizome growth, resulting in a 0.3:1 shoot:root ratio compared with 2:1 for white clover. Both clover species had similar total dry weight after 5 months. Unhindered root/ rhizome devel-opment is very important to hasten the establishment phase of caucasian clover. The caucasian clover lines KZ3 and cool-season, both selections from Monaro, developed seedlings with greater shoot and root growth than cv. Monaro. KZ3 continued to produce greater root growth after 5 months, indicating the genetic potential for improvement in seedling growth rate. Different pasture estab-lishment techniques are proposed that take account of the seedling growth characteristics of caucasian clover. Keywords: establishment, genetic variation, growth, seedling emergence, Trifolium ambiguum

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