Heterosis and combining ability of drought tolerant sorghum [Sorghum bicolor (L.) Moench] genotypes using line x tester analysis

Abstract

Sorghum [Sorghum bicolor (L).Moench] is the leading crop in the arid and semiarid tropics, where drought significantly affects crop production. The use of improved cultivar, in particular hybrid, was found to be the major component as part of the integrated approach of extenuating the extreme effect of drought. A line x tester analysis involving 32 hybrids that resulted from crossing among eight lines and four testers along with two standard checks were studied for 16 characters to generate information on combining ability, gene action and heterosis with respect to growth, phenological and yield and yield components linked to drought tolerance. All 46 entries (32 F1s, 12 parents and 2 checks) were evaluated at drought prone area, Sirinka Agricultural Research Center Kobo trial site, using randomized complete block design (RCBD) with three replications. AGROBASE 20 and SAS version 9.1 were used for analysis of variance (ANOVA) as well as for GCA and SCA analysis. In the analysis the total genotypic variances were partitioned into variation due to lines, testers and their interaction. The GCA and SCA effects were significant for most of the characters studied. The SCA effects were of greater magnitude than GCA effects, which showed greater manifestation of nonadditive gene effects. The ratio of SCA to GCA also revealed predominance of non additive gene effects. Performances of M90950 and P-9529 among the CMS and PDL 984928, WSV 387 and ICSR 161 among the restorers were better for most of the traits. CMS lines P-851015, P-9532 and P-850341 and restorer ICSR 161 and WSV 387 were the best general combiners for most of the traits studied. Mean grain yield of crosses was 3.63 t ha-1 with a range of 2.73 to 5.51 t ha-1. Cross combination P851015xWSV 387 gave the maximum grain yield 5.51 t ha-1. Not a single cross combination showed consistent promising results for all traits, however, the cross combinations P-9532 x PDL 984928, P850341 x ICSR 161, P-851015 x WSV 387, P-9534 x WSV 387 and P- 851063 x WSV387 showed higher specific combining effects for grain yield, number of green leaves per plant and other yield components. Most of the crosses exhibited significant positive heterosis over the mid- parent and standard check value for all traits, however, some of the crosses also depicted negative but desirable heterosis for traits like days to 50% emergency, flowering, maturity and seedling vigor. Generally, this study gave valuable information on the effect of gene action on the performance of crosses as well as identified best general and specific combiners for drought tolerance. However, these should be confirmed further over many locations and seasons.