Agalinis

Figure 1. Haustorium on Agalinis purpurea 24 hours after induction. Reprinted with permission from Dr. Vance Baird.)...

While the activity and the structural specificity of the xenognosins were very encouraging, Astragalus gummifer is native to the Middle East and would not be expected to have co-evolved as a host for the southeastern U.S. native, Agalinis purpurea. The questions of whether molecules of this type were actually exuded from host roots in sufficient quantities to constitute host selection still remained. For that reason, John Steffens switched his attention to Lespedeza... 

Figure 11. Relative activities of haustorial inducers when presented in solution to 2—to-3 week-old plants of Agalinis purpurea. Plants developed an average gf two haustoria each when presented with xenognosin A at 10 M.(13).

Axenic cultures of Agalinis grown in the absence of a host develop few or no haustoria (4,11). Induction of this organ is rapid upon... 

This specificity seemed quite remarkable since Agalinis parasitizes a broad spectrum of hosts. Nevertheless, flavanoids and phenolics have frequently been cited as playing a role in allelopathy (15). Xenognosin A has also been found in Pisum as a... 

Steffens, J.C. et al., Molecular specificity of haustorial induction in Agalinis purpurea (L.) Raf. 

Leguminosae host of Agalinis species, has been described as a haustoria-inducing compound [16]. Glycinoeclipin A is a pentanortriterpene which stimulates the parasitization of the soybean (Glycine max) by cyst nematodes [14]. 

The haustorial inducer from Lespedeza sericea for the parasite Agalinis purpurea, however, proved to be a triterpene, soyasapogenol B (Lynn, 1985). 

As the roots of parasitic plants attach to those of the host plant, a special structure, Ae haustorium, is formed. The formation of haustoria in induced by exudates from the host plant. When the roots of the Agalinis purpurea... 

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