Maize seed orientation in the substrate and its influences on germination, seedling structure, and transmission of Fusarium moniliforme
de Neergaard, E.
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The percentage of seedlings emerging during the first 4 days after sowing and the mesocotyl length after 7 days in sand at 25°C was strongly influenced by the orientation of the seed in the seedbed. Maize seeds emerged faster when oriented vertically with the pedicel end facing down (VD) or horizontally with the embryal side facing up (HU). The mesocotyl portion of the seedling was shorter (t 1mm) when sown at HU and VD, providing a fast and easy emergence to the seedling. It was much longer (20mm) when the seed was oriented horizontally with the embryal side facing down (HD) and vertically with the pedicel end facing up (VU). We concluded that the length of the mesocotyl portion of the seedling varies with the orientation of the seed in the substrate at the same depth. The seeds sown in the orientation HU and VU disclosed a higher germination of 95 percent and 88 percent respectively, compared to the seeds sown in the orientation HD and VD which had 68 percent and 53 percent germination respectively. Seed to seedling transmission of Fusarium moniliforme was recorded at a ratio of 1:1 in the untreated seeds, and infection of the fungus was found in the third leaf lamina and other sections of 10 day old seedlings. This demonstrates for the first time the systemic development of F. moniliforme above the crown portion of 10 day old seedlings. Treatment with Thiram contact fungicide improves the germination of highly infected seeds and also reduces the seed to seedling transmission of F. moniliforme. The efficiency of this seed treatment depended on the orientation of the seeds in the seedbed.