Injection of maize (Zea mays) with Fusarium verticillioides for optimal infection

The optimal spore concentration of F. verticillioides that will be just high enough to cause moderate rotting (infective dosage) in the tissues of maize (Zea mays) stem was investigated. Two inoculation methods viz., toothpick and injection methods were used for the inoculation. Four spore concentration levels of F. verticillioides were employed viz., 1 x 106; 5 x 105; 3 x 105 and 1 x 105 spore/ml. Maize seeds (DMR-LSRW) were planted in several pots in the screenhouse. Four weeks after planting, 5 sets each, of the potted plants were injected on the stems at the second internodes with the different concentration levels of F. verticillioides using both inoculation methods. Inoculation of sterile distilled water served as control. Experiment was conducted in three replications and experimental design was completely randomized design. The stems were later observed and rated for rot severity within the internodes using modified form of Hooker’s scale. Results showed varying extent of rot formation within internodes of stems that received different treatment concentrations of F. verticillioides. Concentration levels of 1 x 106 and 5 x 105 spore/ml of F. verticillioides, for both injection and toothpick methods caused total rotting of inoculated internodes in most plants. Rotting was moderate at 3 x105 spore/ml concentration for both injection and toothpick methods in most plant stands. Concentration level of 1 x105spore/ml had a slightly higher rot formation using toothpick method than using injection method. Rot formation was better with toothpick method than with injection method. 3 x 105 spore/ml inoculum concentration of F. verticillioides could thus be suggested as the appropriate infective but non-lethal dosage that is just high enough to cause infection in tissues of maize stem without killing the entire stem. Toothpick method could also be said to be better than injection method in the inoculation of maize (Zea mays) stem with F. verticillioides.