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Some Characteristics of Rhizobium meliloti Isolates from Alfalfa Fields in Oregon
Author(s) -
Bottomley P. J.,
Jenkins M. B.
Publication year - 1983
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1983.03615995004700060019x
Subject(s) - rhizobium , biology , medicago sativa , inoculation , agronomy , rhizobiaceae , medicago , botany , horticulture , symbiosis , bacteria , biochemistry , genetics , gene
Field populations of Rhizobium meliloti were sampled from root nodules of alfalfa ( Medicago sativa L.) growing in 61 sites in five regions of Oregon. In four of the regions, 60 to 92% of the sites had no previous history of alfalfa. Most probable number (MPN) determinations of R. meliloti in the soils of these regions showed that 50 to 70% of the sites possessed < 10 4 R. meliloti /g of soil, and 17 to 50% had plants showing extremely poor nodulation. Neither preinoculation nor slurry/dusting inoculation practices had been completely satisfactory. In effectiveness studies, only 24 isolates out of 422 evaluated could be classed as superior N fixers. That is, they produced plants equal in weight to nitrate‐grown plants. Twenty‐eight to forty‐four percent of isolates within each region were inferior N fixers, and 40 to 58% of the sites in each region contained 50% or more inferior isolates. Only in 13% of sites were inferior isolates absent. The highest percentage of inferior isolates was found in the Willamette Valley, where most sites had (i) a long history of alfalfa, (ii) the largest soil populations of R. meliloti , and (iii) suboptimum fertility levels.