Influence of artificial lodging at grain-filling stage on plant growth, yield and quality of super rice

Rice lodging has been one of the main constraints to high yield and good quality rice production in China. Because lodging not only makes mechanized harvesting difficult, it also impedes assimilate, water and nutrient transport in grains, limiting the realization of rice yield potential. Lodging conditions under high humidity are prone to diseases and pests, resulting in poor grain quality. In recent years, the potential risk of rice lodging has been increasing because of the release of high-yielding varieties characterized by large panicle, increased nitrogen fertilizer application and shifts from labor-intensive to simplified planting techniques such as direct-seeding or seedling broadcasting. In addition, extreme weather conditions, such as typhoon accompanied with heavy rains at late growth stage, has been another main reason behind lodging, often affecting large areas of croplands. Therefore, it was of utmost importance to further study the mechanisms of lodging-resistance of rice and the related regulation strategies. In this experiment, the effect of artificial lodging at grain-filling stage on plant growth, yield and grain quality of super rice ('Nanjing 9108') was investigated by comparing plants with normal growth (CK), artificial lodging after 30 days of heading (AL30) and artificial lodging after 15 days of heading (AL15). Compared with CK, AL30 and AL15 artificial lodging treatments decreased dry matter production of aboveground organs of 'Nanjing 9108', which resulted in decrease in total dry matter production by 7.3% (P < 0.05) for AL30 and 24.3% (P < 0.01) for AL15. The proportion of biomass distribution in reproductive organs decreased for AL15, but had no significant change for AL30. AL30 and AL15 artificial lodging treatments decreased grain yield by 8.3% (P < 0.05) and 36.4% (P < 0.01), respectively. Yield loss caused by lodging at grain-filling stage was mainly associated with decreases in filled-grain rate and 1000-full-grain weight. Filled-grain rate and 1000-full-grain weight decreased by 5.6% (P < 0.05) and 3.3% (P < 0.05) for AL30, and by 30.8% (P < 0.01) and 6.7% (P < 0.01) for AL15. Lodging-induced decrease in grain weight was mainly associated with smaller brown rice, which was attributed to poorer grain filling at grain-filling stage. Head rice rate decreased by 7.5% (P < 0.05) for AL30 and 14.7% (P < 0.01) for AL15. AL30 treatment had no effect on protein or amylose contents of rice grain, but AL15 increased protein content by 20.2% (P < 0.05). Artificial lodging had no significant effect on RVA profile of rice grain. The results suggested that the effect of plant lodging at late grain-filling stage (30 days after heading) on yield and grain quality of 'Nanjing 9108' super rice was relatively small. In contrast, plant lodging at early grain-filling stage (15 days after heading) inhibited dry matter production and grain-filling process, resulting in yield loss and grain quality deterioration.