Effect of seed hardening, wetting and redrying before sowing, on germination and seedling emergence of a Japanese wheat variety Norin 61 in desiccated soil

Seed hardening, wetting and redrying of the seed before sowing, promotes germination under iow soil-moisture conditions in wheat varieties bred and grown in semi-arid areas. It is unknown, however, whether this is also the case in wheat varieties cultivated in a temperate humid zone. We examined the effect of the seed hardening on germination and seedling emergence under low soil-moisture conditions in a wheat variety, Norin 61, which is cultivated over a wide area of the temperate humid zone in Japan. We first determined the optimum temperature for germination (23°C) and the critical range of soil-moisture (CR) for germination (water-holding capacity of 24%; - 0.30 MPa). Then, we imbibed the seeds of Norin 61 for various periods followed by air-drying, and compared the germination of these seeds and their seedling emergence with those in non-treated seeds at 23°C under CR condition. Imbibition of the seeds for 24 h, which increased the water content to 64%, followed by redrying significantly accelerated the germination and seedling emergence under such conditions. Even in the field, the seed hardening treatment significantly accelerated germination and seedling emergence under both irrigated and non-irrigated conditions. We concluded that seed hardening treatment is available to accelerate the germination of a wheat variety of the temperate humid zone in Japan, Norin 61.