Seed Health Management for Better Productivity - Govind Ballabh ...

(Seed Health Management for Better Productivity)hours conidiophores and conidia were present on pollen grains. In contrast, few conidiagerminated on unpollinated silks by 24 hours and those that did failed to establish significantmycelial growth. Brown silks also supported little growth of fungus, and growth was centratedaround pollen grains.Aspergillus flavus penetrated yellow-brown silks both directly and indirectly through cracksand intercellular gaps. Internal colonization of the silks was restricted to the parenchymatoustissue, and growth was oriented parallel to the silk axis.Internal silk and kernel colonizationAspergillus flavus grows down silks very rapidly. In a controlled-environment chamber witha 34 0 C day and 30 0 C night, a color mutant of A. flavus was recovered from the tip of the ear twodays after inoculation and from the base four days after inoculation. The fungus was found on theglumes of the kernels and adjacent silks six days after inoculation, but not on the seed pericarp.Growth of the fungus from incubated silk segments was first observed from the cut ends, indicatingthat the fungus may move down the silks internally. Such directed growth down the silks couldexplain the rapidity by which the fungus reaches the base of the ear.Kernel infectionThe colonization silks shortly after pollination and the rapid growth of A. flavus down thesilks suggest that the fungus may be following the same path as does the pollen tube, i.e., thestylar canal. Such a route has been proposed for A. flavus.Factors Influencing the Infection Process• Inoculum levels• Drought stress• Temperature- 138 -