SELECTION OF RHIZOBIUM-LEGUMINOSARUM STRAINS FOR LENTIL (LENS-CULINARIS) UNDER GROWTH ROOM AND FIELD CONDITIONS

Most of the production of lentil (Lens culinaris) on the Great Plains occurs on soils that are free of indigenous Rhizobium leguminosarum. Inoculation is required to increase yields through N2 fixation. A screening program to evaluate the effectiveness of R. leguminosarum strains for lentil was initially carried out under controlled environments followed by an evaluation under field conditions. In two separate growth room experiments, the effectiveness of 185 and 24 different strains of R. leguminosarum were tested for Laird and Eston lentil. Significant differences between strains in number of nodules, shoot weight and nitrogenase activity (acetylene reduction activity, ARA) were found for lentil grown for 5 weeks. When lentil were grown for 7 weeks, significant differences between strains in number of nodules, total plant weight, total N, and % N were observed. Fourteen strains plus Nitragin 'C' inoculant were selected for further field testing on Eston and Laird lentil at two locations in 1986 and one site in 1987. Inoculation increased yield up to 135%. Percent Ndfa and total N2 fixed ranged from 0 to 76 and 0 to 105 kg ha-1, respectively. N2-fixing activity was site specific and higher spring soil NO3-levels resulted in lower N2-fixing activity. Depending on site and growing conditions, strains 99A1 and I-ICAR-SYR-Le20 appeared to be superior to the other strains tested. A good agreement was found between the estimates for N2 fixation based upon the 15N-isotope dilution and the classical N difference methods. Number of nodules, dry weight of nodules and ARA of Eston and Laird lentil grown under growth room conditions failed to show positive correlations with total dry matter production, total N or total N2 fixed of field grown lentil. However, total plant weight and total N of lentil grown under growth room conditions were highly correlated with field parameters, and were the most reliable screening parameters for the selection of superior rhizobial strains. © 1990 Kluwer Academic Publishers.