The ability of nodule bacteria of the pea and of the clover groups to infect each other's host plants has been claimed (Wilson, 1939), but these two groups have usually been regarded as distinct and have indeed been given different specific names. The existence in each inoculation group of strains serologically related to some from the other group suggested that certain strains having a specific ability to cross-infect may exist in the two groups (Kleczkowski and Thornton, 1944). The following experiments were made to examine this possibility

Bond, G.

Kleczkowska, J.

Nutman, P. S.

PubMed

Rothamsted Repository

Patron:		Her	Majesty	The	Queen	 	 Rothamsted	Research	Harpenden,	Herts,	AL5	2JQ		Telephone:	+44	(0)1582	763133	Web:	http://www.rothamsted.ac.uk/			 			Rothamsted Research is a Company Limited by Guarantee Registered Office: as above.  Registered in England No. 2393175. Registered Charity No. 802038.  VAT No. 197 4201 51. Founded in 1843 by John Bennet Lawes.		Rothamsted Repository DownloadA - Papers appearing in refereed journalsKleczkowska, J., Nutman, P. S. and Bond, G. 1944. Note on the Ability of Certain Strains of Rhizobi from Peas and Clover to Infect Each Other's Host Plants. Journal of Bacteriology. 48 (6), pp. 673-675. The output can be accessed at: https://repository.rothamsted.ac.uk/item/8ww17.© Please contact library@rothamsted.ac.uk for copyright queries.10/06/2019 14:14 repository.rothamsted.ac.uk library@rothamsted.ac.ukNOTE ON THE ABILITY OF CERTAIN STRAINS OF RHIZOBIFROM PEAS AND CLOVER TO INFECT EACHOTHER'S HOST PLANTSJ. KLECZKOWSKA Arn P. S. NUJTMANRothamsted Experimental StationANDG. BONDDepartment of Botany, Glasgow UniversityReceived for publication July 26, 1944The ability of nodule bacteria of the pea and of the clover groups to infect eachother's host plants has been claimed (Wilson, 1939), but these two groups haveusually been regarded as distinct and have indeed been given different specificnames. The existence in each inoculation group of strains serologically relatedto some from the other group suggested that certain strains having a specificability to cross-infect may exist in the two groups (Kleczkowski and Thornton,1944). The following experiments were made to examine this possibility.INFECTION OF RED CLOVER BY STRAINS DERIVED FROM PLANTS OF THE PEA GROUPIn these tests red clover was grown from externally sterilized seeds on a nitro-gen-deficient mineral salts agar medium in test tubes, previously plugged andsterilized in the autoclave. After germination, the cultures were inoculatedwith the strain to be tested. At Rothamsted, 18 strains of Rhizobium frompeas, beans, and vetches were tested, using 4 parallel tubes, each containing 3 to4 clover seedlings, and 4 uninoculated control tubes which remained withoutnodules. Of the 18 strains, 6 produced totals of from 9 to 22 nodules in the fourtubes, and 6 more strains produced from 1 to 4 nodules. In all cases the firstappearance of nodules was delayed for about six weeks and the nodules whichthen appeared were small and conferred no visible benefit to the host plant.At Glasgow, a similar test was made using 14 strains derived from peas. Ofthese, only one strain produced nodules on clover. This one, however, pro-duced nodules in five out of six replicates. Six control tubes remained withoutnodules.Further tests were carried out with 2 strains that had produced at Rothamsted14 and 17 nodules, respectively, on red clover. The two strains, B and 313,originally derived from peas by the Wisconsin Agricultural Experiment Station,were selected because their serological behavior towards six antisera was knownand because a homologous antiserum against one of them, B, had been obtained.These two strains were reisolated from clover nodules at Rothamsted and inocu-lated onto pea plants, upon which they readily developed nodules. They werethen reisolated from peas and their serological behavior found to be identicalwith that of the original cultures, which had not been passed through clover.An independent cross inoculation test was then made at Glasgow with these673J. KLECZKOWSKA, P. S. NUTMAN, AND G. BONDtwo strains, using the original cultures and those that had been reisolated fromclover nodules. The nodulation produced at Glasgow in 12 replicates was asfollows:No. of tubeswith nodules Total numberCulture on red clover of nodulesPea strain B, original .......................................... 5 11The same, reisolated from clover............................... 4 11Pea strain 313, original......................................... 10 38The,same, reisolated from clover............................... 9 41h Eight uninoculated control tubes remained without nodules.The figures show no evidence that passage through clover produced any adapta-tion increasing the strains' ability to infect this plant.INFECTION OF PEAS BY STRAINS DERIVED FROM CLOVERDifficulty has often been experienced in obtaining nodules on peas grownunder rigidly aseptic conditions, even after inoculation with bacteria from peanodules. For this reason, it was thought best to make preliminary cross inocula-tion experiments with clover nodule bacteria on peas grown in pots of sterilizedsand supplied with a nitrogen-deficient culture solution. The risk of air con-mination was met by using strains of bacteria that could easily be identifiedserologically. Eight strains, originally derived from clover nodules, were tested,and of these, three, strains R, C, and Pentyr 4, produced nodules on peas in 6weeks. Each of these strains was reisolated, passed through clover, reisolated,passed a second time through peas, reisolated, and passed a second time throughclover. After this series of passages the three strains were tested against sixantisera which, in the case of two of the strains, included their homologous anti-sera. All three strains were found to give agglutination reactions identical withthe original cultures which had not been passedthrough peas. In this experi-ment some nodules developed on the control plants, but isolations made fromthese bore no serological resemblance to any of the three strains, R, C, or Pentyr4. These-three strains were then sent to Glasgow, where they were independ-ently tested on peas. This test was made in large test tubes, containing sandand a nitrogen-deficient culture solution, which were plugged, sterilised, andsown with externally sterilised peas. Eleven uninoculated control tubeswereincluded, and all of them remained free from nodules. Ten parallel tubes wereinoculated with each culture. All three strains produced some nodules on thepeas, but only in a few of the replicates. As the peas were harvested after 7weeks, this may have been due to a delay in nodule formation similar to thatobserved in the reciprocal cross inoculation. Concurrent cultures of peas sup-plied with strains originally derived from peas developed plentiful nodules. Thedevelopment of nodules by strains R, C, and Pentyr 4 was as follows:No. of tubeswith nodules Tota numberCulture on peas ofnodulesClover strain R, original culture ................................ 1 4Clover strain Pentyr 4, original culture .......................... 3 31Clover strain C, original culture.................................0 0The same, reisolated from pea at Rothamsted ......... .......... 1 4674RHIZOBIIJM STRAINS INFECTING HOST PLANTSIsolations from the nodules on plants supplied with strains R and C, and froma single nodule that grew in a tube supplied with strain Pentyr 4, were foundto agree in their agglutination reactions with the original cultures. The other 30nodules in replicate tubes supplied with the last strain were found to be con-taminants.In the same experiment, 14 other strains, obtained from clover nodules, weretested on peas, but of these only 4 strains produced nodules.Thus the ability of certain strains of Rhizobium from clover to produce noduleson peas and of certain strains from peas to infect red clover has been confirmedby independent cross inoculation tests made at Rothamsted and at Glasgow.In these tests, strains were cross-inoculated two or three times and, after reisola-tion, were found to agree in serological behavior with the original cultures.The formation of nodules on such cross inoculations, however, took placeonly to a limited extent, and, at least in the case of pea strains on clover, after anunusually long interval. In no case did the host plant derive visible benefitfrom the strain belonging to the other inoculation group. The fact that onlycertain strains will cross-inoculate may explain the disagreement in the findingsof other workers.REFERENCESKLECZKOWSKI, A., AND THORNTON, H. G. 1944 A serological study of root nodule bacteriafrom pea and clover inoculation groups. J. Bact., 48, 661-672.WILSON, J. K. 1939 Leguminous plants and their associated organisms. Cornell Univ.Agr. Expt. Sta., Mem. 221, 48 p.675

Note on the Ability of Certain Strains of Rhizobi from Peas and Clover to Infect Each Other's Host Plants

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Note on the Ability of Certain Strains of Rhizobi from Peas and Clover to Infect Each Other's Host Plants

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