(a) Nodes of Hypocotyl. During last year 2479 sections of the nodes of hypocotyl of different diploid maize seedlings were cultured on the modified MS medium supplemented with a high content of sucrose. The cultures were equally divided into two groups, one was kept in the light (800 lux) with 12-hour daily illumination, and the other was kept continuously in the dark. The temperature was 72 F during the day and 60 F in the night. On the average, six weeks later, about 0.2% of the sections grew into callus. Two weeks later, the calli were transferred to new medium prepared by following the same formula as for the previous culture. These calli are now growing in the culture room. As soon as they have reached a certain size, they will be subjected to further experiments.
(b) Anthers. In the last year, about 3365 anthers having pollen at approximately mononucleate stage, of different strains of diploid maize were grown on modified MS medium with high sucrose content (15%) and 2,4-D (8 mg/l). About 50% of those anthers were kept in light having 800 lux intensity. The period of daily illumination was 12 hours and the average temperature was the same as for culturing the hypocotyl nodes. The other 50% were under continuous darkness. Six weeks after being cultured, about 0.5% of them had grown into callus varying in size; however, none of those calli regenerated into green plantlets, even though some of them were transferred to new media in which NAA was substituted for 2,4-D.
For continued maize anther culture, we have obtained two new strains of maize from the People's Republic of China. Those two maize strains were employed and selected there for anther culture. Both of them successfully grew in vitro into callus and later the calli regenerated into pollen plants.
Y. C. Ting, Anne Boyer, and Greg McSweeney
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