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Effects of Interactions Between Arbuscular mycorrhizal Fungi and Rhizobium leguminosarum on pea and lentil

by Johnny, Liset

Abstract (Summary)
Legumes form tripartite symbioses with arbuscular mycorrhizal fungi (AMF) and rhizobia which influence plant productivity. This study assessed factors that influence the tripartite symbioses between AMF, Rhizobium leguminosarum bv. viceae and pea (Pisum sativum L.) or lentil (Lens esculenta L.), in order to determine if specific combinations of AMF and rhizobia enhanced plant productivity. A survey of soil and plant samples from 12 field sites in Saskatchewan indicated that AMF activity (i.e., number of spores and root colonization) was higher under lentil (n = 7) than pea (n = 5) crops. The efficacy of commercial rhizobia inoculants, reference strains and isolates obtained from root nodules of field-grown pea and lentil was assessed under gnotobiotic conditions. Some strains significantly increased the shoot dry weight and shoot N content of plants, whereas other strains varied in their effectiveness. Effective and ineffective rhizobia strains were selected for co-inoculation studies with AMF in a growth chamber. Results suggest that specific AMF+rhizobia combinations enhanced plant growth and yield. Furthermore, effective AMF can enhance the performance of inferior rhizobia and ' vice versa'. A subsequent study determined the influence of soil-P levels on the tripartite symbiosis. Application of P fertilizer did not alter pea response to either AMF+rhizobia combination, but significantly increased the yield and nutrition of co-inoculated lentil plants. Furthermore, inoculation of pea or lentil with rhizobia or rhizobia+AMF combinations yielded growth equivalent to or better than 20 ppm. of P fertilizer. Selected spore wall bacteria (SWB) isolated from ANF spores stimulated or inhibited the germination of NT4 spores 'in vitro'. The stimulatory SWB enhanced growth and ANF root colonization of NT4-inoculated pea plants, whereas the inhibitory SWB had no effect. However, in the presence of the rhizobia strain LX43, this trend was reversed. My research showed that interactions between AMF, rhizobia and the legume host were specific, and that microsymbiont efficacy, soil-P level, and SWB can alter the outcome of the tripartite symbioses. Therefore, it is important to assess the effect of AMF-rhizobia-legume interactions in the development of commercial inoculants for enhancing legume productivity. (Abstract shortened by UMI.)
Bibliographical Information:

Advisor:Germida, James J.

School:University of Saskatchewan

School Location:Canada - Saskatchewan

Source Type:Master's Thesis

Keywords:no keywords supplied

ISBN:

Date of Publication:01/01/1999

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