Plastid differentiation during androgenesis in albino and non-albino producing cultivars of barley (Hordeum vulgare L.)

In order to better understand androgenic albinism in barley, we compared pl astid differentiation during anther culture in two cultivars, an albino (sp ring cultivar Cork) and a non-albino (winter cultivar Igri) producing culti var: The ultrastructure of plastids and the relative amount of DNA containi ng plastids were followed in both cultivars during the androgenic process a nd correlated with the proportion of regenerated chlorophyllous plantlets. For androgenesis, anthers were collected at the uninucleate stage, during m id- or late-microspore vacuolation. At this stage DNA was detected in 15.3 +/- 2. 7% Of microspore plastid sections in the winter cultivar Igri, compa red to 1.7 +/- 0.5% in the spring cultivar Cork. In the winter cultivar Igr i, starch was broken down after anther pretreatment but plastids divided ra pidly during anther culture and thylakoids developed in the stroma. Prior t o regeneration, plastids contained 2.0 +/- 0.2 thylakoids per plastid and s tarch represented 26.1 +/- 3.3% of the plastid volume. In the spring cultiv ar Cork, plastids followed a different developmental pathway. After anther pretreatment, microspore plastids differentiated exclusively into amyloplas ts, accumulating starch and losing their thylakoids as well as their capaci ty to divide. This developmental pattern became progressively more marked, so that by the end of anther culture plastids contained 0.5 +/- 0.4 thylako ids per plastid and starch represented up to 90.3 +/- 4.3% of plastid volum e. Following androgenesis, the response was similar in both cultivars excep t that the winter cultivar Igri provided 87.8% of chlorophyllous plantlets compared to 99.7% albino plantlets in the cultivar Cork. The results presented here suggest that the exclusive regeneration of albin o plantlets in the spring cultivar Cork may be due to degradation of micros pore plastid DNA during early pollen development, preventing the plastids f rom differentiating into chloroplasts under culture conditions.