Material load from asset bundle are missing texture

hi, i load a lot of small asset bundle for my application, it work well for near everything ( Prefabs, images, meshes ) but when i load a material, the associate texture don't come with it and the standard material in the editor seems strange :

in the .manifest, the dependencies are good :

the PC.manifest :

     Info_53:
       Name: optimiz/materials/matmagnolias
       Dependencies:
         Dependency_0: optimiz/textures/magnolia

the asset.manifest :

 ManifestFileVersion: 0
 CRC: 3409349384
 Hashes:
   AssetFileHash:
     serializedVersion: 2
     Hash: b577b564055f70f5b346428ec5937e35
   TypeTreeHash:
     serializedVersion: 2
     Hash: e3d1bbda6b47c8af72022fe7ef4d8576
 HashAppended: 0
 ClassTypes:
 - Class: 21
   Script: {instanceID: 0}
 - Class: 28
   Script: {instanceID: 0}
 - Class: 48
   Script: {instanceID: 0}
 Assets:
 - Assets/ResourcesBundles/Materials/MatMagnolias.mat
 Dependencies:
 - C:/Users/Dev01/Desktop/WorkSpace Unity4/application/AssetsBundle/PC/optimiz/textures/magnolia
 

if anyone have an idea or a solution, i would be so happy ^^

EDIT :

The problem, in fact, is that when i get the material from the asset bundle, the mainTexture ( the dependencie ) is null, and i don't know why since dependencies are meant to be auto manage...