Nonstructural carbohydrate content in the stubble per unit area regulates grain yield of the second crop in rice ratooning

Abstract

Rice (Oryza sativa L.) ratooning has attracted attention due to its higher yield potential. In the present study, a field experiment on rice ratooning using two rice genotypes, near isogenic line (NIL)-GN1A Takanari and Koshihikari, was conducted in 2019 and 2020 in southwestern Japan to obtain direct evidence for the role of stubble nonstructural carbohydrate (NSC) concentration and/or content per unit area on grain yield of the second crop and to determine the effectiveness of a gene producing more spikelets. NIL-GN1A Takanari is a near isogenic line carrying an allele of GN1A, which is a gene regulating the number of spikelets per unit area derived from an indica cultivar Takanari in the genetic background of a japonica cultivar Koshihikari, and it can produce more spikelets than Koshihikari. NIL-GN1A Takanari did not produce a higher grain yield of the first crop than Koshihikari in both years because NIL-GN1A Takanari had more spikelets m −2 but fewer filled spikelets and a lower grain weight. NIL-GN1A Takanari produced a lower grain yield of the second crop than Koshihikari because NIL-GN1A Takanari had fewer spikelets m −2 due to the fewer panicles. Also, NIL-GN1A Takanari had a lower NSC content than Koshihikari due to the lower leaf sheath plus stem weight in the stubble in 2019. Thus, the lower grain yield in the second crop of NIL-GN1A Takanari may result from the lower NSC content in the stubble. Additionally, the ability to produce more spikelets per unit area of NIL-GN1A Takanari was not demonstrated in ratoon crop under the condition of low NSC content in the stubble.

Grain yield response to planting date and cutting height of the first crop in rice ratooning

“…However, the number of filled spikelets did not differ between cutting heights in 2021 but was higher at low cutting height in 2022. The result in 2021 was in agreement with previous studies (Daliri et al, 2009;Ling et al, 2019;Nakano et al, 2020Nakano et al, , 2022Shahri et al, 2012).…”

“…Several previous studies reported that stubble NSC content per unit area positively correlated with grain yield, the number of spikelets, and the number of panicles of the second crop (Nakano et al., 2020, 2022; Turner & Fund, 1993). Our recent study found that the lack of stubble leaf blade decreased grain yield by decreasing the number of spikelets, number of panicles, number of spikelets per panicle, percentage of filled spikelets, and 1000‐grain weight (Nakano et al., 2021).…”

“…Grain yield is affected by weather and stubble conditions (Nakano et al, 2020(Nakano et al, , 2021(Nakano et al, , 2022Tanaka et al, 2022). We examined the relationships between grain yield and weather and stubble conditions of the second crop (Table 7).…”

“…Cutting height of the first crop is one of the most performed treatments in the study of rice ratooning. Several previous studies reported that the optimal cutting height from the ground surface to obtain high grain yield of the second crop was 40–50 cm (Nakano et al., 2020, 2022) in Japan and 40 cm in Iran (Daliri et al., 2009; Shahri et al., 2012). Similarly, a recent modeling study in China indicated that the optimal cutting height was 40 cm (Ling et al., 2019).…”

Ratoon rice research: Review and prospect for the tropics

“…It has been considered that crop duration of ratoon crop is also regulated by stubble cutting and with low cutting height, crop duration can be extended ( Wang et al, 2020 ). Yang et al (2022) supported this theory, whereas studies from Japan and India had the opposite result ( Nakano et al, 2022 ; Lal et al, 2023 ). This could be also attributed to the varietal difference in adaptation to cutting height.…”