Rapid breeding of ‘Natsuiro’, a new rice cultivar with resistance to high temperatures and rice blast, using genome-wide marker-assisted selection

• Published in: Breeding Research Vol. 25; no. 1; pp. 16 - 23
• Main Authors: Matsumoto, Kengo, Yamakawa, Tomohiro, Ohno, Teppei, Ota, Yuya, Ando, Tsuyu, Yamanouchi, Utako, Yonemaru, Jun-ichi, Tanaka, Junichi
• Format: Journal Article
• Language: Japanese
• Published: Tokyo Japanese Society of Breeding 01.06.2023; Japan Science and Technology Agency
• Subjects: background selection; blast resistance; Cultivars; Deoxyribonucleic acid; Disease resistance; DNA; DNA marker-assisted selection; Farmers; Genomes; Genotypes; Grain; Heat resistance; High temperature; high-temperature grain-ripening ability; Marker-assisted selection; Oryza sativa; Plant breeding; Production costs; Rice; Rice blast; Ripening; Temperature; Temperature requirements
• ISSN: 1344-7629; 1348-1290
• DOI: 10.1270/jsbbr.22J10

In Japanese rice farming, rice cultivars that can achieve stable sales at high prices while reducing production costs and the environmental footprint are required. Currently, there are only a few early maturing cultivars that can meet the requirements of rice farmers by combining high-temperature grain-ripening ability and disease resistance. ‘Natsuiro’ was bred by rapidly introducing pi21, a rice blast resistance gene derived from ‘Tomohonami’, into the ‘Mie 23’ genetic background, an early maturing rice cultivar with high-temperature grain-ripening ability. In the continuous backcrossing, in each generation from BC1F1 to BC3F1, DNA marker-assisted selection of pi21, in addition to genome-wide marker-based background selection, achieved the desired genotypes in 2 years and 2 months after the first artificial crossings in 2013. After that, after line selection and characterization studies such as productivity tests, an application for cultivar registration was filed six years later in 2019. Compared to ‘Mie 23’, ‘Natsuiro’ has mostly the same agronomic traits except for stronger blast-resistance, slightly longer culm length and panicle length, slightly shorter grain length and slightly smaller 1000-grain weight. The culm length of ‘Natsuiro’ is 10 cm shorter than that of ‘Koshihikari’, and the number of ears is slightly less, resulting in an “intermediate” grass type. The heading dates and maturity dates are 3 and 5 days earlier than those of ‘Koshihikari’, respectively. This cultivar has “very strong” leaf blast resistance enhanced by pi21. The high-temperature grain-ripening ability is the same as that of ‘Mie 23’ and higher than that of ‘Koshihikari’, and the class is “strong”. ‘Natsuiro’ was adopted as a recommended cultivar of Mie Prefecture in 2020. It is expected to be widely distributed as an early maturing cultivar that can meet the requirements of rice farmers by combining high-temperature grain-ripening ability and disease resistance.