Leaf markers for root colonization by arbuscular mycorrhizal fungi in plants

A method of determining a mycorrhizal association of a first plant with an arbuscular mycorrhizal fungus (AMF), said method comprising:

• (a) determining the amount of a blumenol marker for mycorrhizal association in an aerial part of said first plant, wherein said blumenol marker is 11-hydroxyblumenol-C-9-O-Glc and said first plant is a vascular plant selected from a Nicotiana plant, a Triticum plant, a Hordeum plant, and an Oryza plant, optionally wherein said first plant has been brought into contact with an AMF prior to said determining, and wherein said determining comprises taking a sample from said aerial part and measuring the amount of said blumenol marker at a time point between about two weeks and about ten weeks after a said contact with an AMF
• (b) selecting a second plant from one of (i) a second plant wherein said second plant belongs to the same species as said first plant and is free of any association with an AMF, (ii) a second plant wherein said second plant belongs to the same species as said first plant and has an association with an AMF, (iii) a second plant wherein said first plant and said second plant are the same individual at different points in time, optionally wherein said second plant is the same individual at an earlier point in time than said first plant, and (iv) a second plant wherein the mycorrhization status of said second plant is not known;
• (c) comparing said amount of said blumenol marker in said aerial part of said first plant to the amount of said blumenol marker determined in an aerial part of said second plant;
• and
• (d) determining said association of said first plant with an AMF after said comparing step, selected from at least one of
• (i) selecting said first plant for it having a higher amount of said blumenol marker in said aerial part of said first plant as compared to said second plant when said second plant is free of any association with an AMF, and, thereby, having an increased AMF association as compared to said second plant,
• (ii) selecting said first plant for it having a higher amount of said blumenol marker in said aerial part of said first plant as compared to said second plant when said second plant has an association with an AMF or when said second plant is the same individual at a different point in time, or when said mycorrhization status of said second plant is not known, and, thereby, having a higher degree of AMF association as compared to said second plant,
• (iii) selecting said first plant for it having a lower amount of said blumenol marker in said aerial part of said first plant as compared to said second plant when said second plant has an association with an AMF, and, thereby, having a lower degree of AMF association as compared to said second plant, and
• (iv) selecting said first plant for it having an about equal amount of said blumenol marker in said aerial part of said first plant as compared to said second plant when said second plant is free of any association with an AMF, and, thereby, not having an AMF association.