Culm Morphological Traits Contributing to Lodging Resistance in First Generation NERICA Cultivars Under Foliar Application of Orthosilicic Acid Fertilizer

Purpose Lodging resistance in upland rice requires adequate knowledge of the mechanical basis of culm morphological traits (CMTs) with potential for improved structural integrity under orthosilicic acid (OSA) fertilizer. However, assessment of lodging in NERICAs has been based solely on visual scoring which is inadequate to establish resistance to lodging. Methods Ten upland rice cultivars, comprising NERICAs 1 to 8, Moroberekan, andOfadawere grown on loamy-sand soil under four rates (0, 250, 500 and 750 ml ha(- 1)) of OSA. At 20 days after heading, CMTs related to lodging were assessed among the rice cultivars. Results Application of 500 and 750 ml ha(- 1)of OSA gave the highest CMTs with reduced lumen diameter. Lodging resistance index (LRI) varied significantly among the cultivars (0.34 in NERICA 1 to 0.70 inOfada). Moroberekan had the highest CMTs with average LRI (0.47). Using Genotype and Genotype x Environment (GGE) comparisons bi-plot, NERICAs 4,6,7,8 and Moroberekan compared well with NERICA 1 for LRI. Bending stress had the highest but negative significant correlation (-0.74**) with LRI. Conclusions Assessment of CMTs in NERICAs under OSA fertilizer can reveal variations in lodging resistance obscured by visual scoring. OSA fertilizer can improve lodging resistance through increased culm wall thickness and reduced lumen diameter in resistant cultivars such as Moroberekan and NERICA 4. NERICA cultivars with lower LRI will be more desirable to minimize lodging at moderate rate(s) of foliar OSA fertilizer. The need to characterize the CMTs of other NERICAs to establish LRI that confers susceptibility, moderate and high resistance to lodging was emphasized.