We examined the effect of the use of unsealed culture vessels in floating anther culture of rice at the callus induction, callus proliferation and plant regeneration stages. Anthers including mid-to late uninucleate pollen grains were collected from a definite position in an ear on the main culm of the plants under dense planting conditions in pots. The effect of the use of unsealed vessels during the callus induction period was tested with a Japonica rice cultivar, Kirara 397, by the double chamber method. A 90 mm plastic Petri dish for anther culture was placed on a single layer of wet filter paper in the outer Petri dish (110 mm) to prevent contamination and evaporation during the culture period. In the control, the Petri dish for anther culture was sealed with Parafilm. When an unsealed culture vessel was used during the callus induction period, callus induction was promoted, but the rate of plant regeneration from these calli slightly decreased. The effect of the use of an unsealed culture vessel during the callus proliferation period was tested with another Japonica cultivar, Kita-ake. Plant regeneration from the callus slightly increased by the use of an unsealed plastic Petri dish during the callus proliferation period. The effect of the use of unsealed culture vessels during the plant regeneration period was tested with the cultivar, Kita-ake. A larger number of green plants regenerated from the calli in the unsealed test tubes during the plant regeneration period than from the calli in the sealed test tubes. Contamination was negligible during this period. Thus, for the floating anther culture of rice, we recommend the culture of anthers and calli in unsealed vessels to enhance the culture efficiency.

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Waxy mutants induced by mutagens in O. sativa (cv. "Norin 8", "Reimei" and "Nihonmasari") and "O. glaberrima" were investigated for their processing suitability for rice-cake. To confirm their processing properties in response to the ripening temperature, mutants were cultivated under two different ripening conditions, namely ordinary and late transplanting. In the waxy mutant strain derived from "O. glaberrima" the rice-cake showed a very high hardness and pasting temperature compared with "Koganemochi", whereas in the other strains, the rice-cake showed a lower hardness than that of commercial varieties. In most of the strains derived from "Nihonmasari", the hardness of the rice-cake decreased when the ripening temperature increased. It was also observed that, in several strains derived from "Reimei", waxy starch viscosity was remarkably high regardless of the low rice-cake hardening. Although the ripening temperature of the waxy mutants derived from a variety was almost identical, the hardness of the rice-cake, heat gelatinization properties and apparent amylose content were markedly different among the strains. It is considered that the induced waxy mutants with distinguishing traits could become useful breeding materials for the manufacture of new rice processing foods and would be suitable for various processed products required by the rice processing industries.

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