Identification and characterization of new sources of resistance to striga hermonthica among diverse maize germplasm
Karaya, Haron G
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This study was designed to identify and characterize new sources of variations in Striga resistance. Four hundred and twenty (420) maize genotypes which included 370 landraces, 10 improved populations, 36 inbred lines and 4 commercial checks were used both in laboratory and field studies. In the laboratory experiments, preconditioned Striga seeds were dabbed on glass fibre discs and arranged radially away from the source of germination stimulants in petridishes. Striga germination counts were made after 24-48 hours under the light microscope. Field evaluation was conducted under both artificially infested and Striga free plots. Twenty inbred lines of putative diverse resistance sources were crossed in a Line x Tester fashion where 14 inbred lines were designated as females and 6 (IITA) inbred lines as males to generate 84 Fl hybrids. Highly significant differences (P=O.OOl) among the germplasm in terms of production of Striga germination stimulants were exhibited in the laboratory. Landraces CRIC 51, CUBA-T- 31, BRAZ 1758, BRAZ 1279 and VERA 217 had the lowest Striga germination ranging from 3.7- 5.9% and inbred lines were generally found to significantly (P=O.OOl) induce higher Striga germination as opposed to the land races. The best performing land races were CHIS 53, JAMA 8, SNLP 104, PAZM 14140 and CUBA-I-66 and these outperformed the commercial checks with a yield of between 50 and 80% under Striga infestation. The inbred lines ll-30-19 and OSU231//56/44-6-4-17-3 consistently performed well under both Striga free and Striga infested environments. The best performing F1 hybrids yielded an average of 6.8 t/ha which was 127% above the commercial checks. A preponderance of additive gene effects and relatively little dominance gene effects in the inheritance of Striga resistance traits was exhibited. Inbred lines TESTR 151 and OSU231//56/44-6-4-17 were the best general combiners. These studies identified 5 landraces, 2 inbred lines and 15 single crosses as new sources of resistance to S. hermothica which should be of great potential for use in breeding programs in eastern Africa.