Sink production and grain-filling ability of a new high-yielding rice variety, Kitagenki

•Kitagenki is a promising high-yielding rice variety adapted to a cool climate in the Hokkaido region, Japan.•Kitagenki showed the maximum grain yield of more than 1000 g m−2.•Grain yield of Kitagenki was stably superior to the other three varieties.•Kitagenki had higher sink capacity than Tachijoubu and Nanatsuboshi.•Kitagenki had higher grain-filling ability than Kita-aoba, due to higher source ability per spikelet and spikelet fertility.