Chickpea-Ascochyta rabiei interaction as revealed by light and electron microscopic studies

Light microscopic and ultrastructural studies revealed that entry of the fungus Ascochyta rabiei occurred through host stomata in addition to direct penetration caused by dissolution of the host cuticle. Direct entry of the host was mostly at the junctions of the epidermal cell walls. Germ tubes got attached to the host surface and caused dissolution of the host wall to achieve penetration. Fine peg-like structures sometimes issued forth from pycnidiospores proper or germ tubes, possibly for anchoring them to the host surface. Appressorial formation was not common. The site of the host near the bases of glandular hairs was highly favourable for entry by the fungus. Inside the host tissue the hyphae of the fungus ramified through cell wall junctions and the interior of the cells and caused degeneration of host cell cytoplasm and its various organelles. The effect of infection was particularly conspicuous on chloroplasts. Lysis of chloroplast outer membrane and dialation of thylakoids were the most common effects.