Figure 1.
Schematic representation of the developmental phases of rust infection on wheat and example of macroscopic symptoms.
A) Confocal microscopy of isolated haustoria from Pst-wheat infected tissue [34] stained with the lectin Concanavalin A (which has affinity for α-D-mannosyl and α-D-glucosyl groups present in various sugars, glycoproteins, and glycolipids), conjugated to Alexa Fluor 488. B) Massive uredospore production at advanced stages of the stripe rust disease on wheat seedlings. C) Representation of the asexual cycle of Puccinia spp. on wheat. The dikaryotic uredospore (S) lands on the leaf surface and produces a germination tube (GT) within 6 hours. Subsequently, it produces an appresorium (A) over the stomatal aperture and enters to the leaf interior through the stoma (ST), where it differentiates into a substomatal vesicle (SV). Primary infection hyphae (IH) propagate through the leaf, and once in contact with mesophyll cells, haustorial mother cells (HMC) differentiate. These penetrate the host mesophyll cell (MC) wall to form the haustorium (H). The haustorium remains separated from the host cell cytoplasm by the extrahaustorial matrix (EHMx) and the host-derived extrahaustorial membrane (EHM). After the establishment of the first haustorium, secondary hyphae develop, colonize the intercellular spaces, and give rise to more HMCs and haustoria. The cycle is completed within 10–11 days, when the invasive hyphae form sporogenous basal cells in the uredia (U) and thousands of new infective uredospores erupt through the leaf epidermis.