Severe barrenness of maize (Zea mays L.) occurred in 2003 in eastern Hokkaido (Konsen region), one of the coldest areas in Japan. In many fields, tassels with few or no spikelets were observed in the cultivar widely grown in this region. The anthesis date was delayed 7 days from the silking date in the cultivar in the field at Konsen Agricultural Experiment Station (KAES). In July, when the tassels were developing at the 6- to the 9-leaf stage, the air temperature and sunshine hours were much lower in 2003 than in the average year. Therefore, we hypothesized that the barrenness resulted from these specific climatic conditions in 2003. To examine this assumption, we applied low temperature treatment (10ºC for 7 days) to the plants of the cultivar widely grown in this region in 2003 at around the 6- to 9-leaf stage in a greenhouse at KAES. Tassels were formed at the 7-leaf stage, and developed but they did not reach their full-size at the 8-leaf stage. The tassel length was shorter when the plants were subjected to the low temperature treatment, especially at the 8-leaf stage. The days from silking to anthesis was increased by the treatment in 2 of the 3 test years. The present results suggest that the cultivar is sensitive to the low air temperature at the 8-leaf stage for the development of tassels and may result in barrenness.

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