Identification of Rice (Oryza spp.) Landraces with Nitrogen Use Efficiency in Ghana

Abstract

Sustainability in rice cultivation requires increasing yield while protecting the environment against pollution from the over-use of fertilizers through the utilization of varieties that are nitrogen use efficient. Hence, the goals of the study were to: 1) characterize the assembled landraces of rice 2) describe the growth response of rice landraces under different nitrogen levels 3) assess the relationship between yield related traits and NUE components and 4) evaluate the extent of genotypic variations of NUE components and yield related traits among the landraces. Two experiments were conducted in pots and on the field which involved 20 rice landraces tested under two nitrogen levels; (no nitrogen fertilizer application) and low nitrogen (i.e. 50 kg/ha of nitrogen fertilizer). The experiments were conducted in the University of Ghana farm from February 2019 to June 2019. The experimental design for the pot experiment was completely randomized design in a factorial arrangement with three replicates. A split plot design was used for the field experiment with three replicates. Average diversity index was 0.70 and 0.33 for quantitative and qualitative traits respectively. Five clusters were created at a similarity index of 67 % among the landraces. Principal component analysis showed four independent principal components accounted for 71.9 % of the total variation. Root dry weight, leaf length, leaf width, shoot dry weight, number of leaves, plant height, chlorophyll content, culm number and grain yield significantly increased at 50 kg/ha of nitrogen (N) fertilizer. Root length increased by 8.79 % in the absence of N fertilizer. There was a reduction in yield related traits under 0 kg/ha of nitrogen fertilizer compared to 50 kg/ha of nitrogen fertilizer. A significant increase in NUE by 31.72% and 5.73 % in pot and field experiments respectively was observed under no N conditions compared to low N. NUE correlated significantly with filled spikelet, grain yield, panicle length, 1000 - grain weight and Nitrogen Uptake efficiency (NUtE). Genotypic coefficient of variation was lower than its corresponding estimates for phenotypic coefficient of variation in all yield related traits and NUE. It can be concluded that GH1550, GH1801, GH1822 and GH2145 were nitrogen efficient and may be used for cultivation and/or used in future breeding programmes to decipher loci involved in NUE for developing superior varieties.