Fresh weight of vegetative organs improves grain yield prediction in upland rice under pre-anthesis water deficit

Water availability in plant organs is important for survival and yield production but has been underestimated during biomass allocation to organs. Assessment of fresh biomass and moisture content in root, culm and leaf during water deficit stress (WDS) can improve grain yield prediction in upland rice. Four upland rice cultivars, NERICAs 1, 4, 6 and Moroberekan, were subjected to 10-day WDS at reproductive stage. Fresh and dry biomass to organs were taken at the end of stress. Leaf relative water content (LRWC), drought-tolerant degree, soil moisture content, were significantly ( p < 0.01) reduced under WDS. Actual fresh, dry and moisture and their fraction to organs followed a similar trend with culm having the largest weight (14.5 g) and fraction (0.49 g g −1 ). Fresh and moisture fractions to root were higher than that of leaf and vice-versa for dry fractions under a stressed condition. Moroberekan and NERICA 4 maintained a higher fraction of biomasses and moisture to root (0.40 and 0.30, respectively) than leaf and higher LRWC and percentage fertile spikelets at the end of 10-day stress. Actual biomass captured higher variation in yield than fraction of biomass to organs, except for dry biomass. The variation in yield of rice captured are in decreasing order of moisture content (54.82/52.61) > fresh biomass (41.60/34.84) > dry biomass (0.00/22.61) for actual and fraction of biomass to organs, respectively with the leaf accounting for the largest share of this variation. Fresh biomass rather than dry biomass of plant organs can predict grain yield better in upland rice during WDS.