VARIABILITY FOR BRIX AND BIOMASS IN SWEET SORGHUM (SORGHUM BICOLOR [L] MOENCH) CULTIVARS AS INFLUENCED BY PLANT SPACING IN A RAIN-FOREST AGRO-ECOLOGY

Abstract

A field experiment was carried out at two environments (August and September dates of planting) at the Teaching and Research Farm of The Federal University of Technology, Akure, Ondo State, South West, Nigeria with the aim of evaluating variability for brix and biomass in sweet sorghum (Sorghum bicolor [L] Moench) cultivars as influenced by spacing in a rainforest agro-ecology. The experiment was laid out in a split plot design with three replications. Spacing was the main plot while genotype was the sub-plot. Each genotype was planted in a 2-row plot of 5 m length. Plant spacings of 25 cm (intra-row) x 75 cm (inter-row) and 15 cm (intra-row) x 60 cm (inter-row) were used in each replication. The plantings were done on 12th August, 2019 and 14th September 2019 for the first and second dates of planting respectively. Data were collected on plant height (cm), stem girth (cm), emergence count, days to 50% booting, days to 50% heading, days to 50% flowering, brix (%), volume of ethanol (ml), volume of juice (ml), weight of stalk prior milling (kg), weight of juice (kg), weight of fresh baggasse (kg), juice yield (ml/kg), sugar yield per area (g/m -2 ), sugar yield per weight (g/kg), and extraction ratio. The data obtained were subjected to analysis of variance and cluster analysis for each environment (date of planting) and for a combination of the two environments. Mean effects that showed significance were separated using Tukey’s Honest Significant Difference test at 5% level of significance. Components of variance, broad-sense heritability, genetic advance, and rank summation index (RSI) were also estimated. Results revealed that genotypic effect was significant for all characters evaluated within and across environments except weight of fresh bagasse, brix, and weight of stalk prior milling in the second environment. Spacing was significant only for emergence count, juice yield, and sugar yield per weight. For the component of variance, Genotypic coefficient of variation was lower than Phenotypic coefficient of variation for all the traits studied in the two environments. Also, there was moderate to high heritability coupled with high genetic advance as a percentage of mean for most of the traits studied in the two environments except days to 50% booting, days to 50% heading, days to 50% flowering, brix, and weight of stalk prior milling in the second environment. Dendrogram from cluster analysis clustered the accessions into three at distance of 300. Cluster I consisted of one accession (FUTA/19/004), Cluster II comprised of four accessions (FUTA/19/006, FUTA/19/010, FUTA/19/007, and FUTA/15/14) while Cluster III comprised of seven accessions namely, FUTA/19/001, FUTA/19/002, FUTA/19/003, FUTA/19/005, FUTA/19/008, FUTA/19/009, and FUTA/15/09. Results from rank summation index (RSI) revealed that FUTA/19/004 had the overall best performance followed by FUTA/19/008, FUTA/15/14, FUTA/19/010, FUTA/19/006, FUTA/19/007, FUTA/19/003, and FUTA/19/009. Conversely, FUTA/19/002, FUTA/19/005, FUTA/19/001 and FUTA/15/09 had the poorest overall performance.