Field Evaluation of Grain Yield and Tube-Culture Assessment of Shoot and Root Traits in New Rice for Africa Varieties Under Flooded Lowland Conditions

Although lowland rice ecosystems play a vital role in meeting the growing demand for rice in sub-Saharan Africa, the performance of New Rice for Africa (NERICA) varieties and their root traits under flooded conditions remain insufficiently characterized. We evaluated seven NERICA varieties (NERICA 1, 2, 3, 4, 7, 10, and 14) and the japonica cultivar ‘Haenuki’ as a regional reference from Japan in a two-year field trial for grain yield and in a tube-culture experiment for shoot and root traits. NERICA 1 had the numerically highest average yield among the NERICA varieties and did not differ significantly from Haenuki in either year, whereas NERICA 14 had the lowest yield in both years. The variety × year interaction was not significant. Compared with Haenuki, NERICA varieties were generally taller but produced fewer tillers and nodal roots, lower root length density (RLD), and coarser root systems, as reflected by a lower specific root length and fine-to-thick root ratio (FTR). Haenuki had greater RLD in upper soil layers, whereas no significant varietal differences were detected in deeper layers (10–20 cm). Exploratory path analysis indicated that shoot dry weight was positively associated with tiller number and RLD and negatively associated with FTR, while tiller number was positively associated with RLD. These results suggest that RLD is associated with shoot growth in tube culture, and that NERICA 1 may be a candidate for further evaluation among the tested NERICA varieties. Since this study is a preliminary screening, validation under actual field conditions in African lowland environments is needed.