|Kallenbach, Robert - UNIV OF CA - DAVIS|
|Mcgraw, Robert - UNIVERSITY OF MISSOURI|
|Ballatti, Pedro - UNLP BUENOS AIRES ARGENTI|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 1, 1997
Publication Date: N/A
Interpretive Summary: Birdsfoot trefoil (Lotus corniculatus L.) is a plant that is grown as feed for livestock. The plant is a legume, and it is able to use nitrogen from the air for growth. The process is called nitrogen-fixation and many legumes fix nitrogen. The nitrogen-fixation process involves growing birdsfoot trefoil with special bacteria, known as Rhizobia or Bradyrhizobia. The purpose of our research was 1) to compare the growth of wild birdsfoot trefoil from Morocco with domesticated birdsfoot trefoil when grown with commercial strains of nitrogen-fixing bacteria and 2) to determine whether wild bacteria isolated from the wild birdsfoot trefoil were more efficient at fixing nitrogen than the commercial strains of bacteria. Seedlings were individually grown with either commercial or wild strains of bacteria. Some seedlings were also grown without bacteria, but they received some nitrogen to support their nutritional needs. Other seedlings were grown without any nitrogen or bacteria. The wild birdsfoot trefoil grew well with the commercial and wild strains of nitrogen-fixing bacteria. One of the domesticated birdsfoot trefoil varieties used in this study grew best when grown with one of the wild bacteria strains. Without any nitrogen or bacteria the wild birdsfoot trefoil grew nearly twice as well as the domesticated birdsfoot trefoil. When nitrogen was supplied, growth of the wild and domesticated birdsfoot trefoil were equal. Since domestic cultivars of birdsfoot trefoil grew well with the wild nitrogen-fixing bacteria, the wild bacteria might be included in commercial inoculants. The wild bacteria could benefit many birdsfoot trefoil varieties by improving nitrogen fixation and yield.
Technical Abstract: Like many legumes, birdsfoot trefoil (Lotus corniculatus L.) fixes atmospheric nitrogen (N2) in symbiosis with bacteria from the genus Rhizobium or Bradyrhizobium. New genotypes of birdsfoot trefoil from Morocco exhibit rhizomes, which could improve persistence of this forage, but little is known about their N-fixing potential. Seedlings of 'Norcen', 'A.U.Dewey', and RBRC (a bulked, reciprocal cross of rhizomatous accessions G31276 and G31272) were individually inoculated with either commercial strains 0.27, 0.28, 0.30, 1710-2, CB756, or Moroccan strains R.L.5797 or R.L.5758. Control treatments were noninoculated seedlings with and without supplemental N (N+ and N-free, respectively). Seedling mass, number of nodules/plant, nodule mass/plant, nitrogenase activity/ plant, specific nitrogenase activity, and whole plant N concentration were measured 45 d after inoculation. In the N-free treatment, RBRC exhibited nearly twice the seedling mass of either Norcen or A.U.Dewey. In the N+ treatment, seedling mass more than doubled for Norcen and A.U.Dewey when compared to the N-free treatment, while RBRC did not show a significant (P>0.05) increase. Norcen exhibited its greatest seedling mass when inoculated with strain 0.27 while A.U.Dewey exhibited its greatest seedling mass with strain R.L.5797. Under N-free conditions, we speculate that RBRC may alter its N metabolism which permits its superior growth in this situation. The Moroccan strains of rhizobia performed well on the domestic cultivars and might be successfully included in commercial inoculants.