RE: HYB - Embryo Rescue

Walter is right in that attention to detail and technique is  critical.
 
The most significant difference between plant tissue culture and embryo  
culture is the use of hormones. Generally, you do not need them with embryo  
culture, as the embryo is programmed to grow without them. I didn't really want  to 
get into the details here, but a little clarification is in order.  In tissue 
culture, the concentration and proportion of hormones is critical for  the 
stages of development. It is usually species specific. There are many  
references on this subject.
 
As for which media to use, it is not nearly so important as controlling  
contamination. There are many different formulas for the media. By far, the most  
common is Murashige and Skoog, commonly referred to as MS. There are 
variations  in this formula also. I have found that 1/2 strength MS media without  
micronutrients works quite well for embryo culture. By the way, MS  media (which 
was first reported in the literature in 1962) differs  significantly from the 
formula that Randolph used in his early work (reported  in 1945) with embryo 
culture.
 
It is important to make a distinction between embryo culture and embryo  
rescue. It is based on where the embryo comes from. Embryo CULTURE is  the growth 
of the embryo from the complete healthy seed. This is what  Randolph did. The 
reasons he cited were avoiding stratification and reliable  germination. 
Embryo RESCUE is the growth of the embryo from a seed lacking  endosperm. Embryo 
culture is much easier than embryo rescue.
 
Technically, the most difficult part of embryo culture is excising the  
embryo. With embryo rescue, it may be finding a healthy embryo.  However, my 
experience is that few embryo rescue attempts are successful.  Remember that embryo 
rescue is fighting against nature. By failure of the  endosperm to develop 
correctly, it has already been determined that this embryo  should not be allowed 
to live. The results that you get might be spectacular,  the it is more 
likely that the embryo will not develop properly or that the  resultant plant will 
have some terrible flaw. I have a few plants in my  garden and many more that 
died in the test tube to back up this statement.  Perhaps, judicious use of 
plant hormones could help produce a viable plant  from some of these ill-fated 
embryos, but that's an endeavor  that will require much time and effort.
 
 If anyone is interested, I published an anecdotal report of  one of the 
failures in the Review of the Society for Japanese  Irises a few years ago.
 
Dennis Hager
_hager@aredee.com_ (h*@aredee.com) 
 

 
Rita  Gormley
Gormley Greenery
Cedar Hill,  MO
http://www.gormleygreenery.com/

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