Louise Jackson, Debbie Miller, Sally Smith

Lettuce (Lactuca sativa) is a crop with high water and nutrient demand. Its nearest wild relative, L. serriola, is tolerant of low moisture and nutrient-poor conditions. Due to selection in different types of environments, the two taxa may differ in response to arbuscular mycorrhizae (AM), symbiotic fungi associated with the roots of almost all plants.

Pot experiments were used to determine if mycorrhizal colonization, growth, root allocation, and P and N tissue concentrations differed between the two Lactuca taxa when inoculated with Glomus intraradices (Jackson et al., 2002, Scientia Horticulturae).

• Both taxa had strong and generally similar responses of mycorrhizal colonization and growth to P availability.
• Plant N acquisition was enhanced by mycorrhizal symbiosis, presumably because exploration of the soil volume was increased.
• Mycorrhizae were more effective at scavenging N from low vs. higher soil N treatments, probably because colonization was higher.
• Use of wild lettuce for breeding improved cultivars of lettuce will at least maintain any ability to benefit from mycorrhizas, since especially in organic farming systems with low P inputs, for which cultivated lettuce tends to have high colonization levels (Miller and Jackson, 1998, J. Agric. Sci. Cambridge).

References

Jackson, L.E., D. Miller, and S.E. Smith. 2002. Arbuscular mycorrhizal colonization and growth of wild and cultivated lettuce in response to nitrogen and phosphorus. Scientia Horticulturae 94: 205-218

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