Figure 1.

In vitro and in planta evidence of Calonectria hemileiae antagonistic/biocontrol effect on Hemileia vastatrix.

Urediniospores of H. vastatrix suspended in sterile distilled water (SDW) and germinating after 6 hr incubation in vitro (A, bar 50 μm). Conidia of C. hemileiae suspended in sterile distilled water (SDW) and forming germ tubes and branching – note germinating conidia of C. hemileiae (black arrows) (B, bar 50 μm). C. hemileiae (Ch) in combined suspension in SDW with urediniospores of H. vastatrix—note germinating conidia of C. hemileiae (black arrows) and short and inflated germ tubes emerging from urediniospores (white arrows) (C, bar 50 μm). Coffee leaf discs (D to I) and plants (K to P) from experiments that involved C. hemileiae applications at 72 hr before (G and N) or simultaneously (H and O) with inoculation of H. vastatrix (E and L). Effect of fungicides (trifloxystrobin + tebuconazol) (I and P) on H. vastatrix. Leaf discs and coffee plants sprayed with sterile water (D and K) and C. hemileiae (F and M) without inoculation with H. vastatrix used as controls. Rust disease index (RDI) (J) and coffee leaf rust severity (CLRS) (Q) for coffee plants submitted to different treatments. Asterisks (∗) indicates significant difference (p ≤ 0.05) by the Dunnet-test. Bars represent the standard deviations. n = 3 and 5, respectively, for experiments involving leaf discs and coffee plants. Scanning electron microscopy micrographs showing a healthy pustule of H. vastatrix producing a group of urediniospores (arrowed) on the leaf surface (R, bar 20 μm) and a pustule of H. vastatrix overgown by C. hemileiae, showing collapsing urediniospores (arrowed) (S and T, bar 20 μm) 20 days after spraying with a C. hemileiae conidial suspension.