A Challenge to Achieve High Yield in Newly Developed Rice Cultivar ‘Tsukiakari’ in Hokuriku Regions

A newly developed early maturing and high palatability rice cultivar Tsukiakari has been disseminated in the Hokuriku region. It showed 10% higher grain yield than an early maturing rice cultivar Akitakomachi. This study aimed to clarify the high-yielding characteristics of Tsukiakari through the multi-environmental testing in the Hokuriku region. A total of 47 yield trials during 2017–2019 revealed that the grain yield of Tsukiakari reached a plateau around 750 g m–2. From the significant linear regression among grain yield, yield components, and shoot nitrogen content in Tsukiakari, the values obtained were 35,700 spikelets per square meter, 423 panicles per square meter, 83.8% of filled grains, 25.1 g of one-thousand grains, and 14.0 g m–2 of shoot nitrogen content at a grain yield of 750 g m–2. The percentage of perfect grains and grain protein content was estimated to be 72.5% and 7.1% at a grain yield of 750 g m–2 using the significant linear regression with spikelet number per square meter, which was developed using the data set obtained in 2017–2018 and 2017–2019, respectively. Note that the percentage of perfect grains in 2019 was much lower than that in 2017–2018 due to an extremely high temperature during ripening. Calculated culm length of Tsukiakari at a grain yield of 750 g m–2 was 80.4 cm, and it is expected to avoid lodging at maturity up to approximately 80 cm. Overall results indicate that Tsukiakari is an elite cultivar that can achieve high yield and grain quality without lodging if rice plants are not subjected to an extremely high temperature during ripening.