Effects of different water management practices on the dry matter production process and characteristics in NERICAs

Abstract

In this study, we aimed to clarify the effects of different water management strategies on dry matter production and yield performance of New Rice for Africa (NERICA) varieties. Dry matter production of NERICA 1 and NERICA 5 was compared with that of Yumenohatamochi, a Japanese upland variety, and Hinohikari, a Japanese lowland variety under three water regimes, i.e. continuously flooded, supplemental irrigation, and non-irrigation (rainfed). Total carbohydrate content in the panicles under different watering regimes was more closely related to post-heading photosynthates than pre-heading reserve assimilates. Dry matter production during ripening tended to decrease under low soil water conditions, whereas the dry matter translocated from the leaf and stem to the panicle tended to increase. Consequently, the distribution ratio of post-heading photosynthates in the total carbohydrate content declined in response to the reduction in available soil moisture. These results indicate that the total carbohydrate content vary depending on the soil water conditions. In NERICAs, dry matter production during ripening was lower than that in Japanese varieties, indicating that their dependence on pre-heading reserve assimilates was greater. In particular, post-heading photosynthate content of NERICA 1 was strongly affected by the variation in water management in comparison with that of other varieties. The decrease in crop growth rate during ripening in NERICA 1 can be mainly attributed to the lower post-heading photosynthate content. Thus, the ability of NERICA 1 to assimilate carbon after heading was considered to be potentially low, which has to be improved to achieve higher yield.

The outstanding rooting1 mutation gene maintains shoot growth and grain yield through promoting root development in rice under water deficit field environments

“…These results are consistent with the findings reported by Kikuta et al. (2019) that reduced crop growth resulting from decreased NAR from the panicle initiation to maturity stage suppressed dry matter production and grain yield under intermittent irrigation.…”

“…Specifically, water stress decreases the leaf photosynthetic rate, thereby reducing NAR (Lu et al. 2000; Praba et al., 2009) and RGR shows a much stronger correlation with NAR than with LAR under water deficit conditions (Kikuta et al., 2019). These findings suggest that the our1 ‐type genotypes maintained a high growth rate from the heading to maturity stages under AWD through increased photosynthetic ability (Table ), resulting in higher dry matter production and grain yield.…”

“…Therefore, the ability to promote root development, particularly LR formation, is a desirable attribute for efficient water and nutrient uptake from large soil areas (Suralta et al., 2018). Under low soil moisture conditions, whole SDW during ripening decreased due to decline in photosynthetic rate because of low root activity (Kikuta et al., 2019). Thus, the high yield and growth rate in the our1 ‐type genotypes under AWD might be attributed to the high photosynthetic ability maintained by enhanced root development and root function until the maturity stage.…”

“…The shoot‐to‐root ratio was calculated as the shoot dry weight (SDW) divided by the root dry weight. The total carbohydrate content of the panicles, composed of post‐heading photosynthates and translocated pre‐heading reserve assimilates, was calculated as described (Kikuta et al., 2019). The dry matter translocated from the leaf and stem to the panicle during ripening (pre‐heading reserve assimilates) was quantified from the dry weight of the leaf sheaths and stems from the heading to maturity stages.…”

Morpho-physiological and molecular mechanisms of phenotypic root plasticity for rice adaptation to water stress conditions

“…Thus, lateral root formation may be induced by carbohydrate allocation, which is supported by the exogenous glucose application that promotes L-type lateral roots (Lucob-Agustin et al 2020c). Recently, Kikuta et al (2019) observed that some drought-tolerant rice varieties could use basal shoot starch for root development during the heading period for the maintenance of yield production under water-limited conditions. These studies highlighted a novel physiological action of both the shoot and root in the regulation of root plasticity in rice.…”