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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #135119
Title: VARIED RESPONSE OF MARIGOLD GENOTYPES TO INOCULATION WITH DIFFERENT VA MYCORRHIZAL FUNGI

Author
item Linderman, Robert
item DAVIS, E - OSU BOTANTY & PLANT PATHO

Submitted to: Scientia Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/2002
Publication Date: 1/1/2004
Citation: Linderman, R.G., Davis, E.A. 2004. Varied response of marigold genotypes to inoculation with different VA mycorrhizal fungi. Scientia Horticulturae. v99 p. 67-78.

Interpretive Summary: Most plants form an association between their roots and special soil fungi called mycorrhizae. Mycorrhizae can greatly aid plants, especially under environmental or disease stresses. The largest type of mycorrhizae, called vesicular-arbuscular mycorrhizae (VAM) are believed to be relatively non host specific, i.e. the VAM fungi are able to form an association with most any plant. However, there is an accumulation of observations that not all host plants are equally colonized or responsive. It was the purpose of this study, therefore, to carefully evaluate the relative responsiveness of a genetically narrow group of marigold plants in order to document differences in host specificity and preference by several VAM fungi. There were, in fact, significant differences in host response as well as extent of root colonization by the different VAM fungi. One fungus, Gigaspora albida, did not colonize any marigold genotype, even though it readily colonized onion roots. These results indicate that there can be considerable variation in host responsiveness due to some genetic control by the host, and apparently some preference shown by the fungal symbiont as well. This information underscores the need for caution in predicting benefit from inoculation with VAM fungi under commercial conditions where many different genotypes are grown.

Technical Abstract: Different genotypes of marigolds were evaluated for colonization and responsiveness to inoculation by different VA mycorrhizal (VAM) fungi under low P conditions. Included were Tagetes erecta 'Jubilee', 'Perfection', 'Antiqua', 'Inca', and 'Discovery' as tall and compact forms of the African-type; T. patula 'Aurora', 'Disco', 'Nemagone', and 'Lemondrop' as dwarf types with single or double flowers; and T. signata 'Ursula' as a fine-leaf Mexican-type. Considerable variation occurred in shoot and root biomass response depending on the genotype and VAM fungus used. Plants of most genotypes responded minimally (total plant biomass) but positively to inoculation with VAM fungi (1-22%, compared to the nonVAM controls); however, some combinations resulted in reduced total plant growth (1-12%, compared to the nonVAM controls). Genotypes varied in their biomass partitioning into roots or shoots, with some partitioning more into roots than others with similar shoot biomass. There was also great variation in the extent of VAM colonization, ranging from under 10% to over 70% by Glomus intraradices, G. mosseae, and G. deserticola; notably, Gigaspora albida did not colonize any marigold genotype. Intraradical colonization intensity ratings (arbuscules, vesicles, and internal hyphae) varied significantly among cultivars and VAM fungal inoculants, as did extraradical hyphal development. These results document the potential variation in responsiveness that can occur depending on host genotype and VAM fungal endophyte combination, and indicates the need for caution in predicting benefit from inoculating with mycorrhizal fungi under any set of conditions when different genotypes are grown.