Influence of Genotype, Growth Stage and Temperature Variations on Anti-Nutritive Properties of Potential Fodder Sorghum in Kenya

Abstract

Sorghum [Sorghum bicolor (L.) Moench] is a fodder crop that thrives well in tropical climates and can offer solution to the feed shortage in Kenya. The aim of this study was to evaluate the influence of genotype, stage and temperature variations on major anti-nutritive quality attributes of selected fodder sorghum genotypes. Three experiments were conducted in the field, greenhouse and growth chamber to obtain data for evaluating the effect of temperature on lignocellulose and Hydrocyanic acid potential (HCN-p) of selected fodder sorghum cultivars. In the field experiment, twenty sorghum cultivars obtained from ICRISAT, commercial varieties and farmers‘ collections were evaluated in a randomized comple block design in 3 locations with vatying temperatures {(Egerton-cool), and (Marigat-hot) respectively} in 2019 nd 2020. Sorghum plants were sampled at booting and dough stages of development to determine the lignocellulose content and hydrocyanic acid potential (HCN-p). The second experiment, which was conducted in and outside a greenhouse under natural light was laid out in a CRD with three replicates, was set up to determine the effect of varying temperature on the HCN-p of sorghum genotypes using five sorghum genotypes. The third experiment consisted of three potted sorghum genotypes: IS11442, IESV91105LT and E6518 grown in the greenhouse then later transferred to a growth chamber. The three genotypes were subjected to controlled temperature and relative humidity. The temperature settings were 35oC/15oC, 25oC/10oC and 18oC/8oC). Analysis of variance was done through generalized linear model in R statistical software version 4.3.0. Treatment means were separated through Tukey‘s honest significant difference (HSD) test at P≤0.05. There was a significant increase in HCN-p and lignin content from a cooler region (Egerton), to a warmer region (Rongai) through to a hotter region (Marigat). HCN-p in the test material ranged from 83 – 147 ppm. The lowest values of HCN-p were obtained from the brown mid-rib (bmr) genotypes; IS 23787, EST 36 and EST 37 whose content were 86.58, 86.24 and 84.43 ppm, respectively, in 2019 and 85.13, 85.73 and 83.79 ppm in 2020. Temperature had a significant effect on HCN-p of sorghum as shown by higher HCN-p in sorghum that was grown in the greenhouse (117.5 ppm) compared to that grown outside the greenhouse (101.5ppm) as well as sorghum held at high temperature (35/15oC) in the growth chamber. Based on lignin content and HCN-p, EST 20, B 35, IS23787 and EST 37 sorghum lines are recommended for safe sorghum fodder provision when harvested at dough stage and grown in cool or warm environments.