Figure 2: Pre-penetration and penetration of Puccinia arachidis through epidermal cell on groundnut variety TMV 2 during 1–3 days after inoculation (dai). A. Pre-penetration encompassing germ tube (Gt) and appressorium (App) formation from a single urediniospore (U). Attachment of the appressorium to the epidermal cell resulting in necrosis (brown discoloration) of the attacked epidermal cell. B. Formation of penetration hypha (Ph, arrow) at the site of appressorial attachment. C. Penetration hypha (Ph, arrow) traversing the epidermal cell. D, E and F. Initiation of Primary hypha (prh, arrow and inset) and traversing across the intercellular spaces of mesophyll at 3 dai. Leaves were stained with trypan blue and observed with differential interference contrast microscopy using Olympus BX 51 microscope. Scale bar represents 20 µm.

Figure 3: Post-penetration of Puccinia arachidison six groundnut genotypes observed during 3–5 days after inoculation (dai). In the susceptible genotypes TMV 2 (A) and K-6 (B), extensive growth of the fungus in the intercellular spaces of mesophyll and presence of haustoria in the mesophyll cells were clearly seen at 4 and 5 dai. In the moderately resistant genotypes ICGV 17015 (C) and ICGV 13229 (D), two events were observed simultaneously between 3 and 5 dai. While the fungus attempted to spread between the intercellular spaces of the meosphyll cells, the host attempted to arrest the spread of hyphae through initiation of defence as evident by mesophyll cell death (visualized by retention of trypan blue stain). In the resistant genoytpes ICG 11426 (E) and GPBD 4 (F), the growth of P. arachidis inside the mesophyll was arrested by extensive mesophyll cell death visualized by the retention of trypan blue stain at 3 to 4 dai. Leaves were stained with trypan blue and observed with differential interference contrast microscopy using Olympus BX 51 microscope. Scale bar represents 20 µm.

Figure 1: Pre-penetration and penetration of Puccinia arachidis through stomata on groundnut variety TMV 2 observed during 1–3 days after inoculation (dai). A. Pre-penetration encompassing germ tube (Gt) and appressorium (App) formation from a single urediniospore (U). B and C. Penetration by formation of penetration hypha (Ph) through the stomata at 1–2 dai. D and E. Primary hypha (Prh, inset) traversing into the intercellular spaces of mesophyll. F. Formation of haustorial mother cell (Hmc, inset) at 3 dai on the mesophyll cells. Leaves were stained with trypan blue and observed with differential interference contrast microscopy using Olympus BX 51 microscope. Scale bar represents 20 µm.

Figure 3: Post-penetration of Puccinia arachidison six groundnut genotypes observed during 3–5 days after inoculation (dai). In the susceptible genotypes TMV 2 (A) and K-6 (B), extensive growth of the fungus in the intercellular spaces of mesophyll and presence of haustoria in the mesophyll cells were clearly seen at 4 and 5 dai. In the moderately resistant genotypes ICGV 17015 (C) and ICGV 13229 (D), two events were observed simultaneously between 3 and 5 dai. While the fungus attempted to spread between the intercellular spaces of the meosphyll cells, the host attempted to arrest the spread of hyphae through initiation of defence as evident by mesophyll cell death (visualized by retention of trypan blue stain). In the resistant genoytpes ICG 11426 (E) and GPBD 4 (F), the growth of P. arachidis inside the mesophyll was arrested by extensive mesophyll cell death visualized by the retention of trypan blue stain at 3 to 4 dai. Leaves were stained with trypan blue and observed with differential interference contrast microscopy using Olympus BX 51 microscope. Scale bar represents 20 µm.

Figure 1: Pre-penetration and penetration of Puccinia arachidis through stomata on groundnut variety TMV 2 observed during 1–3 days after inoculation (dai). A. Pre-penetration encompassing germ tube (Gt) and appressorium (App) formation from a single urediniospore (U). B and C. Penetration by formation of penetration hypha (Ph) through the stomata at 1–2 dai. D and E. Primary hypha (Prh, inset) traversing into the intercellular spaces of mesophyll. F. Formation of haustorial mother cell (Hmc, inset) at 3 dai on the mesophyll cells. Leaves were stained with trypan blue and observed with differential interference contrast microscopy using Olympus BX 51 microscope. Scale bar represents 20 µm.

Figure 2: Pre-penetration and penetration of Puccinia arachidis through epidermal cell on groundnut variety TMV 2 during 1–3 days after inoculation (dai). A. Pre-penetration encompassing germ tube (Gt) and appressorium (App) formation from a single urediniospore (U). Attachment of the appressorium to the epidermal cell resulting in necrosis (brown discoloration) of the attacked epidermal cell. B. Formation of penetration hypha (Ph, arrow) at the site of appressorial attachment. C. Penetration hypha (Ph, arrow) traversing the epidermal cell. D, E and F. Initiation of Primary hypha (prh, arrow and inset) and traversing across the intercellular spaces of mesophyll at 3 dai. Leaves were stained with trypan blue and observed with differential interference contrast microscopy using Olympus BX 51 microscope. Scale bar represents 20 µm.