2022 Volume 91 Issue 4 Pages 315-321
Field experiments using a high-yielding rice cultivar ‘Hokuriku 193’ and two progeny lines were conducted across three years in Nagano Prefecture, the highest-yielding area for rice in Japan. The characteristics of growth, dry matter production, yield and yield components were compared at the high yielding level of over 1200 g m–2 for rough brown rice. The two progeny lines of ‘Hokuriku 193’ showed lower shoot dry weight than ‘Hokuriku 193’ owing to growth duration shortened by early heading. The abundance of available carbohydrate for grain filling represented by the sum of stem non-structural carbohydrate at full heading and dry matter increase during grain filling tended to be lower in the two progeny lines. The total grain number was higher in line A than in ‘Hokuriku 193’ while the thousand grain weight was lighter. The sink capacity represented by the product of grain number and weight were similar or slightly smaller. The ratio of filled grain was similar to that of ‘Hokuriku 193’ or slightly lower. The brown rice yield of line A was lower than ‘Hokuriku 193’. On the other hand, the sink capacity of line B was improved by a heavier thousand grain weight with similar grain number. The ratio of filled grain was lower. As a result, brown rice yield of line B was similar to that of ‘Hokuriku 193’ despite shorter growth duration. Given that earlier heading can avoid low temperature during grain filling, line B is a promising line for Nagano prefecture.
