**4. Pollen fertility restoration in diverse cytoplasmic sterility lines for improved populations**

Superimposed on the major forces of evolution is variation due to the interaction of the mitochondria (cytoplasm) and nuclear genes in mediating resistance to some major stresses and physiological processes in the plant that needs to be exploited to enhance genetic variation. This material is useful in developing hybrids, inbred lines and gene pools based on combining ability for specific traits (components of grain yield). The study identified testers and restorers for extraction of lines from improved populations for yield-related traits such as; seed size, plant height panicle length, panicle width and resistance to stem borers.

### **4.1 Population development**

The experiment was designed to make improvements in quantitative traits to maximize as much as possible the additive effects, maternal, as well as to gather genes with complementary dominant and epistatic effects in genotype. The hypothesis tested was that Hybrids derived from inbred lines (A-lines) with complementary heterotic groups have superior performance. (**Table 7**). A two-way cross hybrids were generated from seven pollinator testers of (*Sorghum bicolor*) with drought tolerant backgrounds mated to A2 cytoplasmic sterile lines using an appropriate model [17]. The lines used were selected from previous studies (1–3) perceived to be containing favorable alleles for the prioritized traits of; robustness (vigor), large seeds, disease resistance and high threshing percentage. Data was analyzed using NCII model appropriate to line × tester crossing design with two reps in the 2022 A season. The variance between the testers was subdivided into variance within cytosteriles and that due to interaction.
