S. Van Bergen et al., The role of abscisic acid in induction of androgenesis: A comparative study between Hordeum vulgare L-cvs. Igri and Digger, J PL GR REG, 18(3), 1999, pp. 135-143
Under the same mannitol pretreatment and culture conditions, regeneration e
fficiency in the barley cultivar. (cv.) Igri was about 10 times higher than
in the cv. Digger, a difference only partially reflected by a difference,i
n viable microspores after anther pretreatment. Therefore, a comparative st
udy between cvs. Igri and Digger was carried out under various pretreatment
conditions. For both cultivars, under water, CPW buffer and mannitol pretr
eatment conditions, there was a positive correlation between microspore via
bility and regeneration efficiency in that mannitol > CPW buffer >> water.
Mannitol pretreatment of cv. Igri produced a much higher endogenous abscisi
c acid (ABA) level than as to Digger. Addition of ABA stimulated both perce
ntages of viability and regeneration efficiency except in the case of manni
tol pretreatment. Under CPW buffer pretreatment conditions, addition of ABA
significantly stimulated regeneration efficiency and was ABA concentration
dependent. However, cv. Digger was less responsive to ABA than cv. Igri. I
n both cultivars, under less optimal pretreatment conditions (e.g., water a
nd CPW buffer), the effect of ABA was to stimulate increased percentages of
viability and/or to reduce the number of binucleate microspores. Moreover,
in cv. Igri, direct culture of anthers for 4 days without pretreatment cau
sed an increased number of binucleate microspores compared with microspores
with pretreatment for 4 days. These binucleate microspores showed DNA degr
adation in the nuclei. However, with mannitol pretreatment binucleate micro
spores and DNA fragmentation in the nuclei of microspores was rarely observ
ed. On the basis of our observations, we suggest that the difference in reg
eneration efficiency:in cv. Igri and cv. Digger is related to the differenc
es in endogenous ABA production levels under mannitol pretreatment and resp
onsiveness to ABA. One of the effects of ABA is likely due to an inhibition
of cell death.