PERFORMANCE AND EXPRESSION OF STAY GREEN INTROGRESSED SORGHUM [Sorghum bicolor (L.) Moench] GENOTYPES FOR POST FLOWERING DROUGHT STRESS UNDER FIELD AND GREENHOUSE ENVIRONMENTS

Abstract

Drought is among the most important obstacles in agriculture that retard the production as well as productivity of the crops across the entire world. Since sorghum is highly produced from arid to semi-arid tropics, it is one of the staple and strategic crops for farmers. However, there are a number of constraints that reduces production and productivity of sorghum in the country. Stay greenness resulting in higher grain per mass yield and lodging resistance to boost sorghum grain yield (GY) in the face of post-flowering dryness. The experiment consisted a total of 56 lines for evaluation. From which 36 lines are BC2F4 stay-green introgressed sorghum lines crossed with B35 using marker-assisted backcrossing (MAB), fifteen elite lines from ICRISAT, two recurrent parents, one donor parent and two OPV checks (Melkam and Argiti) were evaluated. It was laid out in 4x14 alpha lattice design under both field and greenhouse environments during 2020/21, respectively. These introgressed sorghum lines had one or more of the four stable stay-green QTLs (Stg1 to Stg4) from the donor parent B35. This evaluation was done to examine the performance and expression of stay green introgressed sorghum lines for post-flowering drought stress under irrigated in green house and rain-fed environments in Ethiopia. The Analysis of Variance (ANOVA) showed highly significant (p≤0.05) variation for most of the studied traits under field condition except for stand count at harvest and number of heads per plot. For the greenhouse experiment, ANOVA, highly significant (p≤0.05) difference was recorded for most traits except days to flowering, days to maturity, stay green, stand count, number of heads and hundred seed weight for non-stress part and drought score, stay green, stand count, number of heads, chlorophyll content and hundred seed weight for the stress condition. The over location field experiment analysis showed that the minimum and maximum grain yield was 0.93 and 4.38 t ha-1 , respectivelyThe controlled greenhouse experiment grain yields ranged from 1.2 to 6.9 t ha-1 and 1.1-5.1 t ha-1 for the non-stress (optimum) and stress conditions respectively. The GCV and PCV for combined analysis of field experiment ranged from 1.55 (number of heads per plot) to 42.20% (grain yield) and 7.51 (days to maturity) to 46.06% (grain yield) respectively. For greenhouse non-stress experiment, the GCV and PCV ranged from 1.15 (days to maturity) to 37.14% (stem lodging) and 4.57 (stand count at harvest) to 38.79% (plant height) in respective order. The greenhouse stress experiment GCV and PCV values ranged from 1.60 (days to maturity) to 25.03% (grain yield) and 3.30 (days to maturity) to 37.15% (grain yield) respectively. Genetic advance as percentage of mean and broad sense heritability for the combined field experiment ranged from 0.25(harvest index) to 79.63% (plant height) and 1.00(dry biomass) to 94.00% (Chlorophyll content) respectively. Heritability and genetic advance for non-stress greenhouse experiment ranged from 0.13 (stand count) to 94.26% (drought score) and 2.25 (dry biomass) to 73.27% (harvest index) respectively, however, under stress condition it ranged from 5.20 (number of heads per plot) to 97.24% (plant aspects) and 2.99 (number of heads per plot) to 34.72% (grain yield), respectively. Combined analysis of the field locations declared high heritability coupled with GAM for plant height and chlorophyll content. The field experiment showed that grain yield had positive and highly significant correlation with number of heads per plot, harvest index, plant height, dry biomass, stay green and hundred seed weight both at genotypic and phenotypic level. Under non stress conditions of the greenhouse experiment grain yield had positive and highly significant correlation with harvest index, dry biomass, stem lodging and hundred seed weight, while the stress part grain yield had positive and highly significant correlation with dry biomass and harvest index both at genotypic and phenotypic level. Stay green is highly correlated with drought score and grain yield under field experiment, whereas it is correlated with days to maturity and dry biomass under non-stress and stress conditions respectively. The clustering approach Unweighted Pair Group Method with Arithmetic Means (UPGMA) grouped the 56 sorghum genotypes evaluated at field, greenhouse non-stress and stress condition in to IV, III and IV clusters, respectively. In general, the variation found in the tested genotypes supported the idea that sorghum genotypes could be improved through selection and hybridization to increase yield for the study area