In this section:
Acid Tolerant Lucerne and Rhizobia
DEVELOPING LUCERNE AND RHIZOBIA WITH IMPROVED TOLERANCE TO ACIDIC SOILS: A NOVEL APPROACH
contact: alan.humphries@sa.gov.au
SUMMARY
A multidisciplinary approach to improving the tolerance of lucerne and rhizobia to acid soils is being pursued, involving the selection of plants, rhizobia and the symbiosis between plants and rhizobia.
Lucerne plants have had 4 cycles of selection for improved root length in solution culture at low pH with toxic levels of aluminium. In greenhouse trials, lucerne selections grown in acidic soils, collected from Victoria and NSW, showed an increase in root mass of between 0 and 225% and an increase in shoot mass of 0 to 26% compared with commercial cultivars.
Two hundred and twenty strains of rhizobia were isolated from acidic soils under mature lucerne stands in NSW. Solution screening has shown that at least 4 of these strains are able to nodulate 50% of lucerne plants at pH 4.8 compared with less than 10% of plants nodulated with the commercial strain (RRI 128). One of these strains (SRDI 675) almost doubled plant nodulation compared to the commercial strain when it was used to inoculate lucerne plants grown in an acid soil collected from Inman Valley, SA.
Solution culture screening has also shown variation among lucerne populations for their ability to nodulate at pH 5. Plants with pink nodules after 4 weeks of growth in this system have been recovered in a nitrogen free environment and then crossed to generate the 1st cycle of lucerne population with improved nodulation.
We have worked in this area for almost 10 years to develop successful screening systems and subsequently select plants and rhizobia that are tolerant to acidic soils.
Screening lucerne for improved nodulation in acidic solution culture
