Previous PageTable Of ContentsNext Page

Nodulation and growth of serradella at low root temperatures

R. A. Ballard

Department of Agriculture, Kybybolite, SA 5262

Poor growth of serradella, Ornithopus spp., during the winter months has been largely attributed to a deficiency in the legume/Bradyrhizobium symbiosis. Selection of strains of Bradyrhizobiurn lupini which result in quicker nodulation and/or better nitrogen fixation at low root temperatures could markedly improve the production of serradella. This study examines effect of strains of B. lupini on nodulation and growth of serradella at two root temperatures.

Methods

Six inoculation treatments (uninoculated, uninoculated plus nitrogen and B. lupini strains WU425, WSM471, USDA3709 and NA419) were imposed on two cultivars of serradella (Tauro and Grasslands Koha) were grown at a root temperature of 9 or 20C. Plants were grown in glass tubes with shoots exposed to the atmosphere. Nitrogen (1 mg as KNO3) was added at 12, 19, 26, 33 and 40 days after inoculation (DAI) to plants assigned to the nitrogen treatment. The mean ambient shoot temperature during the experiment was 23/13C (day/night). Shoot weight and nodulation (1) were determined at 23, 33 and 43 DAI.

Results and discussion

At a root temperature of 20C, inoculated plants were well nodulated by 23 DAI. Continued nodulation and rapid plant growth were a feature in subsequent harvests (Table 1).

At a root temperature of 9C, inoculated plants were only poorly nodulated at 23 DAI. Although the nodulation of these plants subsequently increased, little shoot growth occurred. The addition of nitrogen was the only treatment which resulted in a substantial growth response of plants grown at 9C by 43 DAI. The poor response of plants at 9C to nitrogen until 33 DAI indicates delayed nodulation had little effect on shoot growth . From 33 to 43 DAI increases in the nodulation of these plants failed to increase shoot growth, suggesting symbiotic nitrogen fixation was limiting. Significant growth response to added nitrogen at 9C (43 DAI) suggests there may be considerable merit in the selection of cold tolerant strains of B. lupini.

References

Howieson, J.G. and Ewing, M.A. 1989. Aust. J. Agric. Res. 70, 843-850.

Previous PageTop Of PageNext Page