**4.2 Combining ability**

Testers varied significantly for all characters (**Tables 7** and **8**). The differential behavior of the genotypes was reflected in general combining ability (GCA) effects. Variance for GCA is greater than the variance for specific combining ability (SCA) implying large additive gene effects and over-dominance effects. There is a possibility of deriving superior lines from such populations containing balanced cumulative effects of genes. Lines with highly significant positive GCA effect such as DINKIMASH-17 for grain yield could be useful for contributing favorable alleles for breeding for improved grain yield under drought conditions. Female inbred lines; ICSA 12, CK60A, P 9518A and ICSA 90001 and the male lines GE30, KAK-7780, NAROSORGH4, IESV98038/2SH and DINKIMASH-17, were selected for their desirable GCA effects for agronomic traits.


*SCA = specific combining ability, GCA = General combining ability, Var = variance, \*\*\*=significant at 0.01 probability, \*\*p = 0.1, \*p = 0.05, ns = not significant, DF = degrees of freedom, PHT = Plant height, PANL = Panicle Length, GNW = Grain weight, GRNYLD = Grain yield per hectare.*

#### **Table 7.**

*Analysis of variance for key yield components.*


#### **Table 8.**

*Estimates of general combining ability for top 10 ranking genotypes.*

Test cross F1-derived F2 families have been developed by exploiting differences in the cytoplasm (**Table 8**). The identified lines have a positive effect on fertility restoration. The effect of genes carried was likely large enough to influence the full seed set of the panicles among many families. The Partial sterility observed among some F1S does not present a serious problem because the F1 may be either selfed/backcrossed to recurrent parent Populations. This permits the best exploration of the intricate assortment of both major genes and genes with small effects for the traits under consideration [19]. The breeding products from this study are important in enhancing sorghum germplasm base by contributing favorable alleles for expressing vigor of yield and cytoplasmic pest and disease-mediated resistance [20].

*DOI: http://dx.doi.org/10.5772/intechopen.112322 Accelerating Breeding for Drought Tolerance in Sorghum (*Sorghum bicolor*): An Integrated…*
