Histopathology ofAlbugo tragopogonison stems and petioles of sunflower

摘要

Stem lesions in sunflower caused byAlbugo tragopogonis(Pers.) S.F. Gray developed individually from primary infections and did not result from a systemic infection. Cell division and callose formation were not observed, but weak lignin deposition occurred in infected tissues. Hyphae occurred intercellularly in stems in the cortex, cambium, vascular rays, and pith. In petioles parenchymatous tissue was heavily colonized in contrast to lightly colonized collenchymatous hypodermis. The middle lamellae of cells in infected tissue were dissolved, and cells degenerated and eventually collapsed. Stem infections lead to deterioration of tissue integrity, weakening of stems, and finally to lodging of stems (breaking over).Key words:Albugo tragopogonis,Helianthus annuus, histopathology, stem lodging.