Some Limiting Factors and Improvement for the Overwintering Ability of Spring Wheat Sown before Continuous Snow Cover.

Abstract

It has been known that spring wheat sown immediately before continuous snow cover has higher quality and yield than that sown in spring in the heavy snowfall areas of Hokkaido. To increase the stability of the overwintering of spring wheat sown before continuous snow cover, some limiting factors for overwintering and improvement of wintering ability were studied. The number of germinated seeds increased from the 30th day under snow, and thereafter seminal root and coleoptile elongated. Though the seeds reached their germination percentage measured at 20°C before the 40th day under snow, the percentage of overwintering plants after snow thaw largely decreased. Under snow, snow mold (Typhura ishikariensis) on plants sown before continuous snow cover was observed, which seems to affect the overwintering ability. Germinating seeds at 20°or 2°C before sowing did not improve their overwintering ability. A low germination percentage did not affect overwintering ability, but a smaller number of plants and number of panicle per area decreased grain yield. These results suggest that overwintering ability was not related with the germination process, but it was limited by injury after germination under snow. Overwintering ability was improved by the use of large seeds, more than 2.2mm in diameter, which also affected rapid growth after snow thaw and increased grain yield. It was suggested that large seeds containing much nutrient can enhance plant growth under snow and especially regrowth after snow thaw.