Since the first success in obtaining pollen-plants of maize in 1975 (Ku et al.), much effort has been made by many workers with maize anther culture. Considerable progress has been achieved in this field of research. However, the number of responding genotypes is limited, and almost all of them are Chinese or United States germplasm. In our experiment, we used Japanese and Chinese germplasm reserved in The National Institute of Agro-Biological Resources in Tsukuba, Japan, and some American dent hybrids and an introduced synthetic.
In 1983-1984, over five plantings, plant materials were grown in a greenhouse. Tassels with anthers containing uninucleate or early binucleate microspores were detached and incubated at 8 C for 14 days. After the cold treatment, tassels were sterilized with a saturated solution of calcium hypochlorite and anthers were plated in Yu-Pei medium containing casamino acid 500mg/l, sucrose 120g/l, activated charcoal 5g/l and TIBA 0.1mg/l. At the second planting in 1984, we used three different media, described in Table 2. Plated anthers were incubated at 25 C in the dark. After 30-60 days in culture, callus or embryoid formation was observed.
The response was different between genotype (Table 1): 5 American dent genotypes did not respond at all, but 11 of 14 Japanese genotypes and 5 of 6 Chinese genotypes responded. The frequency of responding anthers was low, and induction frequencies of most genotypes were under 1.0%. The highest response was 1.2% attained in the Japanese local variety 'Aso'. However, wide variation in induction frequency was observed among individual plants as well as among varieties, especially in 'Aso' and 'Kijiyama 33'. The values were 9.3-0% and 12.0-0%, respectively. The variation among individual plants was estimated to be caused by both genetic and environmental factors, and it may be possible to improve the response by selecting highly responsive plants and making hybrids among the selected plants. Though the differences of media were indistinct, Yu-Pei medium was somewhat more effective than N6 medium (Table 2).
Calli or embryoids formed were transferred to regeneration medium (Yu-Pei medium containing sucrose 30g/l, kinetin 1mg/l and other elements same as induction medium) and incubated at 25 C, 14h day length. In this condition, some calli and embryoids regenerated root or shoot: six formed roots and four formed shoots, but no plantlet was obtained. On the other hand, some of the embryoids on B medium (Table 2) were transferred to 16hr light condition without change of medium, and three embryoids grew into plantlets.
Table 1. Variation in callus and embryoid formation by anther culture in different origin of varieties in maize (1983 - 1984, 5 plantings).
Table 2. Effect of culture medium on callus and embryoid formation *(1984 2nd planting)
Keiichi Koinuma, Noboru Mochizuki and Yasuaki Inoue
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