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Epistasis of rj1 Nonnodulation of Soybean to Nodulation by Sinorhizobium fredii
Author(s) -
Rasooly Avraham,
Isleib T. G.
Publication year - 1993
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1993.0011183x003300020023x
Subject(s) - biology , bradyrhizobium japonicum , inoculation , bradyrhizobium , epistasis , sinorhizobium , genetics , microbial inoculant , symbiosis , allele , gene , genotype , rhizobiaceae , botany , horticulture , bacteria
Utilization of highly efficient N‐fixing, improved strains of Bradyrhizobium japonicum in soybean [ Glycine max (L.) Merr.] inoculants has been hampered because these strains cannot compete in the rhizospbere with indigenous strains. Development of host genotypes that selectively nodulate with introduced strains could improve the field response of soybean to inoculation. Our objective was to determine whether Sinorhizobium fredii USDA 205 could overcome the nodulation block in soybean plants homozygous for the rj1 gene. The rj1 gene produces a nonnondulating phenotype with most strains of B.japonicum . ‘Peking’ is homozygous for the recessive allele conferring the ability to nodulate with S. fredii . Peking was crossed with an isoline of ‘Harosoy’ bearing rj1 . We identified F 2 plants homozygous for the recessive allele for S. fredii nodulation by selecting for the ability to form nodules with S. fredii . F 3 progeny of these F 2 selections segregated for the ability to nodulate with B. japonicum 110, indicating segregation for rj1 . The results indicate that the two traits are controlled by different loci that are not tightly linked. In a separate test, F 2 plants homozygous for rj1 were selected and allowed to self. Ten seeds from each of four F 2 rj1 plants were inoculated with S. fredii , but none formed nodules, showing that rj1 nonnodulation is epistatic to nodulatlon by S. fredii . We surmise that rj1 cannot be used in conjunction with an S. fredii inoculum to overcome the problem of bacterial competition for nodule occupancy.