DIFFERENTIAL EXPRESSION OF UPLAND RICE TRAITS AS INFLUENCED BY SOIL-MOISTURE CONDITIONS

The identification of traits that contribute to high crop quality, especially grain yield, is a major step in planning for trait introgression in rice genotypes. Blanket  recommendation of certain cultivars for cultivation across ecology gradients fails to take full advantage of genotype-environment compatibility in terms of superior expression of plant traits. A study was thereby conceived to identify traits that confer distinct genotypic performance under each cultivation condition.Twenty upland rice genotypes comprising interspecific NERICA (Oryza sativa x Oryza glaberrima) and two local ‘Ofada’ selections were cultivated under natural rainfall, in three locations along a toposequence in a derived savannah ecology with intermittent mid-season to terminal drought. The same genotypes were grown in the screenhouse on the toposequence soils with adequate moisture and imposed reproductive stage moisture stress. Genotype, soil and moisture effects produced significant differences in trait expression. Trait heritability estimates were generally low, the highest was 28.3 for leaf dry weight (LDW) on the field and 33.1 for tiller number (TN) in the screenhouse. There were inconsistencies in the traits that best described genotype performance under different growth conditions. Across the growth conditions,TN leaf number (LN), culm dry weight (CDW), panicle number (PN), grain weight per panicle (GWPPN) and grain weigh per plant (GWPP) were identified by factor and discriminant analyses as the foremost traits in describing rice response under adequate moisture and panicle stage moisture stress. Genotype plus genotype-by-environment interaction (GGE) biplots captured between 61.6% and 75.8% of the genotype variation for GWPP and PN respectively, clustered different growing conditions into groups for different traits but identified genotypes (NERICA) 6, 7 and 14  as having across environment adaptation for CDW, GWPPN and PN respectively.