I found this paper in the literature; hope will be useful to you.

Thanks,

Ram Singh

There are a variety of kits that may still help with good RNA extraction.

Here is a paper that compares a few Plant RNA Kits for isolation from some challenging woody grapevine samples in this case:

http://bit.ly/1N8G98c

and a poster that compares various kits for RNA extraction from a range of plant types.

http://bit.ly/1TBXo8B

Hope this is helpful

Thanks a lot Ram J Singh, i will have a look in this paper, it seems that they use a similar method i was using before (but for sugar beet)

Thanks also Tom, but i am specially looking for a isolation method without using a kit. But thanks for your links, i will also check them!!