Potential to breed for mycorrhizal association in durum wheat

The selection of genotypes under high soil fertility may have altered the effectiveness of mycorrhizal symbioses naturally forming between crop plants and the mycorrhizal fungi residing in cultivated fields. We tested the hypothesis that the mycorrhizal symbiosis of five landraces function better than the mycorrhizal symbiosis of 27 cultivars of durum wheat bred after the development of the fertilizer industry. We examined the development of mycorrhiza and the response of these genotypes to mycorrhiza formation after four weeks of growth under high and low soil fertility levels in the greenhouse. The durum wheat genotypes were seeded in an established extraradical hyphal network of Rhizophagus irregularis and in a control soil free of mycorrhizal fungi. The percentage of root length colonized by mycorrhizal fungi was lower in landraces (21%) than in cultivars (27%; P = 0.04) and in the most recent releases (29%; P = 0.02), which were selected under high soil fertility levels. Plant growth response to mycorrhiza varied from –36% to +19%. Overall, durum wheat plant breeding in Canada has increased the mycorrhizal development in wheat grown at low soil fertility level. However, breeding had inconsistent effects on mycorrhizal development and has led to the production of cultivars with patterns of regulation ranging from unimproved to inefficient.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author