EVALUATING INTRA-ROW SPACING TO OPTIMIZE STRIGA INFESTATION FOR RESISTANCE SCREENING IN SELECTED MAIZE GENOTYPES

Abstract

Striga hcrmonihica (Del.) Benth, is considered the greatest biological threat to maize production in sub-Saharan Africa. The success in breeding for resistance to Striga depends on a high and uniform field infestation with the parasite. One of the factors that can optimize infestation of maize plants with Striga is intra-row spacing. The objective of this study was, therefore, to assess the effects of different intra-row spacing of maize hills on Striga infestation. Five different maize genotypes were infested with 5000 germinable Striqa seeds in the field at intra-row spacings of 20 cm, 25 ern, 33 cm, and 50 ern. The experiment was conducted at Mokwa (901S'N lat., 5004E long., 457 m altitude and 1100 mm annual rainfall), for two seasons and at Abuja (9016'N 'lat., 7020'E long., 300 m altitude and 1500 mm annual rainfall), for one season in Nigeria. There was high significant (P< 0.001) location influence on Striga emergence, host plant damage scores, plant height, stalk lodging, ear height and grain yield. High significant differences (P< 0.00 1) were also exhibited among the genotypes for all these parameters. Differences in intra-row spacing significantly affected Striga emergence' count, host damage symptoms, stalk lodging, ear aspect and grain yield. Location x genotype interaction was highly significant (P< 0.001) for host plant damage scores, plant height (non-infested plots), ear aspect scores (infested plots) and grain yield (infested plots). There was a significant (P< 0.05) in fraction of location x spacing for stalk lodging in the infested plots. Mean square for genotype x spacmg interaction was not significant in each test environment, suggesting that the same intra-row spacmg may be used to effectively screen maize genotypes of different genetic backgrounds. On the average, the 20 em intra-row s pucmg had 100</';)more Striqa emergence than the 50 em intra-row spacing that is currently used on trials by breeders and scientists. However, the 20 em intra-row spacing produced the lowest grain yield under non-infested condition because of severe competition among maize plants within the row. The 25 em spacing gave high Striga emergence and host-plant damage symptoms as well as acceptable grain yield for all genotypes. Ba scd on the results or this study, it ('(111 therefore be concluded that in order to have a successful resistance breeding for Striqa with high and uniform field infestation and to optimize the present artificial field infestation technique, the 25 ern intra-row spacing should be adopted for field screening by breeders and scientists for effective separation of reaction of genotypes to Striga.