<p>A total of 36 root‑nodule bacteria were isolated from southern Ethiopia using the Red Wolaita common bean variety, and 26 were authenticated as rhizobia and then screened for symbiotic effectiveness in a greenhouse at Arba Minch University. Among the authentic isolates, strains AMU23, AMU74, and AMU3A had symbiotic effectiveness values of 138%, 117%, and 116.7%, respectively, and were further evaluated along with a commercial strain, HB429, in farmers’ fields at varying altitudes with the Red Wolaita common bean variety. The selected rhizobial isolates were introduced by seed inoculation with coal‑based formulations prepared under controlled laboratory conditions, along with a commercial reference inoculant. In the field trial, the native strain AMU23 showed the highest nodule number (138.3), nitrogen derived from the atmosphere (84%), and grain yield (2.24 tons ha⁻¹), with superior production‑induced traits and larger effects at the lower altitude (Arguba site, 1160&#xa0;m.a.s.l.). On the other hand, the strain AMU74 had the highest performance at the higher altitude (Tegecha site, 2174&#xa0;m.a.s.l.), suggesting that native strains’ symbiotic efficiency and yield improvement were influenced by altitude. However, their effectiveness was also influenced by soil fertility parameters and environmental factors. In comparison, the commercial strain exhibited significantly lower grain yield and symbiotic performance (<i>p</i> &lt; 0.05) than the native strains at both locations, yet it still improved productivity, indicating the superior efficacy of the locally sourced strains over the commercial inoculant. A multi‑locus sequence analysis (MLSA) clustered the native strains within the <i>Rhizobium etli–Rhizobium phaseoli</i> species complex, including <i>Rhizobium etli CFN42 and Rhizobium phaseoli VMW4</i>, whereas the commercial strain HB429 clusters tightly with the <i>Rhizobium etli</i> strain HBR51.</p>

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Agro‑ecological and Genetic Drivers of Symbiotic Efficiency of Indigenous Rhizobium etli Strains in Common Bean in Southern Ethiopia

  • Meseretu Melese,
  • Endalkachew Wolde-meskel,
  • Ashenafi Hailu Gunnabo

摘要

A total of 36 root‑nodule bacteria were isolated from southern Ethiopia using the Red Wolaita common bean variety, and 26 were authenticated as rhizobia and then screened for symbiotic effectiveness in a greenhouse at Arba Minch University. Among the authentic isolates, strains AMU23, AMU74, and AMU3A had symbiotic effectiveness values of 138%, 117%, and 116.7%, respectively, and were further evaluated along with a commercial strain, HB429, in farmers’ fields at varying altitudes with the Red Wolaita common bean variety. The selected rhizobial isolates were introduced by seed inoculation with coal‑based formulations prepared under controlled laboratory conditions, along with a commercial reference inoculant. In the field trial, the native strain AMU23 showed the highest nodule number (138.3), nitrogen derived from the atmosphere (84%), and grain yield (2.24 tons ha⁻¹), with superior production‑induced traits and larger effects at the lower altitude (Arguba site, 1160 m.a.s.l.). On the other hand, the strain AMU74 had the highest performance at the higher altitude (Tegecha site, 2174 m.a.s.l.), suggesting that native strains’ symbiotic efficiency and yield improvement were influenced by altitude. However, their effectiveness was also influenced by soil fertility parameters and environmental factors. In comparison, the commercial strain exhibited significantly lower grain yield and symbiotic performance (p < 0.05) than the native strains at both locations, yet it still improved productivity, indicating the superior efficacy of the locally sourced strains over the commercial inoculant. A multi‑locus sequence analysis (MLSA) clustered the native strains within the Rhizobium etli–Rhizobium phaseoli species complex, including Rhizobium etli CFN42 and Rhizobium phaseoli VMW4, whereas the commercial strain HB429 clusters tightly with the Rhizobium etli strain HBR51.