Abstract

Six elite sorghum varieties, ICSV 111, ICSV 400, KSV 4, Gaya Early, CS 54, and CS 95 were used to improve Striga resistance through pedigree breeding. SRN 39 and IS 9830 varieties were confirmed resistant to Striga hermonthica (Del.) Benth in field trials. The two Striga resistance lines were crossed with the six elite varieties. Three hundred and sixty Striga-free plants from F₂s of good agronomic traits were identified, and selfed to produce F₃s. The number of selections varied from 12 (ICSV 400 x IS 9830) to 59 (ICSV 400 x SRN 39) per F₂ population. About 50% more plants were selected from the crosses involving SRN 39 as donor parent for Striga resistance than the crosses involving IS 9830. In addition, 58 out of the 100 plants selected were from a cross, ICSV 111 and SRN 39. Crosses from which Striga free plants were obtained were CS 54 x SRN 39 (12 plants selected), CS 95 x SRN 39 (9), ICSV 400 x SRN 39 (6), Gaya Early x IS 9830 (6), Gaya early x SRN 39 (5), and KSV 4 x IS 9830 (4). Crop syndrome reaction score was higher in 1995 (2.3 - 4.0) than in 1996 (1.0 - 2.7). Our results suggest that SRN 39 is a better donor parent for Striga resistance than IS 9830.  ICSV 00090 NG, a cross between ICSV 111 and SRN 39 gave the highest grain yield of 2.02 t/ha in a replicated trial compared to the two parents, ICSV 111 (1.11 t/ha) and SRN 39 (0.86 t/ha). This variety combines potential for high yield and resistance to Striga. Our data indicates that the elite varieties can be improved forStriga resistance using pedigree breeding. A large F₂ population (500 to 1000 plants per cross) is recommended for the selection of transgressive segregants. Further efforts are required to back cross-promising segregants with established Striga resistant variety in order to develop durable Striga resistant varieties with acceptable agronomic traits.

Key words. Sorghum, Striga hermonthica, parasitic weed, resistance.