Table 3 Comparison of morphological characters and dimensions, and temperature-growth relations of Phytophthora palmivora, P. frigida, P. alticola (from original description, holotype and paratype material and living isolate CMW 19425 = CMW 34279), P. boodjera, and P. arenaria.
Species and sources of data | P. palmivora (Erwin & Ribero, 1995) | P. frigida (Maseko 2007) | P. alticola (holotype 1 ) PREM 59215 | P. alticola (paratype 2 ) PREM 59217 | P. alticola (Maseko 2007) | CMW 34279 3 (this study) | P. boodjera (this study) | P. arenaria (Rea 2011) | P. arenaria (this study) |
|---|---|---|---|---|---|---|---|---|---|
No of isolates | 10 | 10 | 1 | 12 | 10 | 9 | |||
Sporangia (mm) | |||||||||
LxB mean | 45.3 × 29.8 | 33 × 37 | 31.1 ± 5.0 × 30.9 ± 4.5 | 36 × 28 | 38.9 ± 5.4 × 28.6 ± 4.3 | 39.2 ± 4.4 × 29.7 ± 3.4 | 31.8 ± 4.6 × 23.7 ± 3.5 | 23.9 ± 3.1 × 19.8 ± 3.4 | |
Range | 40–60 × 25–35 | 24–40 × 20–33 | 27.7–45.7 × 23.0–29.4 | 30–45 × 20–35 | 20.4–60.7 × 19.0–38.9 | 15.2–64.5 × 13.9–42.5 | 20.2–53.0 × 12.5–35.0 | 12.7–38.5 × 9.9–30.7 | |
Range of isolates means | na | na | 32.6–44.6 × 24.7–33.3 | 28.9–34.8 × 21.4–28.3 | 19.5–24.9 × 16.0–23.1 | ||||
L/B ratio | 1.2–1.8 | 1.22 | 1.21 ± 0.12 | 1.4 (<1.6) | 1.35 ± 0.03 | 1.27 ± 0.16 | 1.40 ± 0.17 | 1.22 ± 0.20 | |
Range of isolates means | na | na | 1.19–1.35 | 1.2–1.5 | 1.08–1.65 | ||||
Sporangial characteristics | Papillate | Papillate, rarely bipapillate | Papillate | Papillate, rarely bipapillate | Papillate, rarely bipapillate or bilobed | Papillate, rarely bipapillate or bilobed | Papillate, rarely bi/tripapillate or bilobed | Papillate, rarely bipapillate or bilobed | |
Persistence | caducous | caducous | semi-caducous | caducous | persistent | persistent | persistent | persistent | |
Sporangiophores | Lax or close sympodia | simple | Lax or close sympodia | simple or branched sympodia | simple or branched sympodia often with bulbous base, very often laterally attached | simple or branched sympodia often with bulbous base, very often laterally attached | simple or branched sympodia often with bulbous base | simple or branched sympodia often with bulbous base, very often laterally attached | |
Sporangia shape | ellipsoid, ovoid spherical | ovoid, sometimes obpyriform | Usually ovoid to broad ovoid | usually ovoid or ellipsoid, sometimes obpyriform or peanut-shaped | ovoid 66%, limoniform 14%, peanut-shaped 8%, obpyriform 6%, distorted 6% | ovoid 64%, limoniform 20%, peanut-shaped 10%, distorted 6% | usually ovoid, also obpyriform or distorted | ovoid 40%, subglobose 20%, globose 14%, obpyriform 12%, distorted 4% | |
Proliferation | absent | absent | absent | absent | absent | absent | absent | absent | |
Exit pores (mm) | |||||||||
Width | 5–6 | 6 | 6.21 ± 0.53 | 6.09 ± 1.02 | 6.00 ± 1.00 | 5.50 ± 0.95 | |||
Width range | 5–10 | 4–8 | 5.00–7.10 | 4.85–8.89 | 3.40–8.90 | 3.88–7.10 | |||
Chlamydospores (mm) | 32–42 | 24–26 | 42.6 ± 5.8 | Some isolates 28 (20–35) | absent | absent | absent | absent | |
Hyphal swellings | Spherical | Irregular | Catenulate, some with radiating hyphae | Catenulate, some with radiating hyphae | Catenulate, globose to sub-globose, some with radiating hyphae | Catenulate, globose to sub-globose, some with radiating hyphae | |||
Mean diameter (mm) | na | 14.7 | 15.2 | na | 12.8 | ||||
Breeding system | Heterothallic | Heterothallic | Homothallic | Homothallic | Homothallic | Homothallic | Homothallic | Homothallic | |
Oogonia (mm) | |||||||||
Mean diameter | 38 | 26.2 ± 2.3 | 284 | 27.3 ± 1.9 | 29.4 ± 2.3 | 25.3 ± 2.2 | 26.6 ± 1.6 | ||
Diameter range | 22–34.8 | 24–48 | 24–37 | 20–35 | 22.03–31.07 | 24.3–33.9 | 19.6–34.3 | 20.5–29.6 | |
Range of isolates means | na | na | 24.6–33.4 | 24.3–28.1 | 23.6–28.8 | ||||
Oospores (mm) | |||||||||
Mean diameter | 22.8 ± 0.1 | 33 | 26.2 ± 2.1 | 30 (28.3 × 30.5) | 24.9 ± 2.1 | 25.5 ± 1.9 | 22.3 ± 1.8 | 23.8 ± 1.6 | |
Diameter range | 22.8 | 25–42 | 21–31 | 24–36 | 20.3–29.5 | 20.92–29.3 | 16.0–28.3 | 17.8–28.6 | |
Range of isolates means | na | na | 21.3–29.5 | 21.4–23.9 | 21.5–25.9 | ||||
Wall thickness | na | 2.51 ± 0.4 | 2.47 ± 0.33 | 2.30 ± 0.34 | 2.57 ± 0.22 | ||||
Oospore wall index | na | 0.57 ± 0.01 | na | 0.54 ± 0.05 | 0.47 ± 0.05 | 0.50 ± 0.05 | 0.53 ± 0.06 | ||
Oogonial characteristics | Aplerotic | Aplerotic | Aplerotic | Markedly aplerotic, oospores with thick inner walls | Aplerotic oospores Mature oogonia with a slightly wavy surface and golden-brown discoloration often with tapering base | Aplerotic oospores Mature oogonia with a slightly wavy surface and golden-brown discoloration | Aplerotic oospores Mature oogonia with a slightly wavy surface and golden-brown discoloration | Aplerotic oospores Mature oogonia with a slightly wavy surface and golden-brown discoloration | |
Antheridia | Amphigynous | Amphigynous | Amphigynous | Mainly amphigynous | Paragynous, often with finger-like projections | Paragynous | Paragynous, often with finger like projections | Paragynous | |
LxB mean (mm) | na | 10.6 ± 2.3 × 8.3 ± 1.4 | 10.4 ± 1.9 × 8.3 ± 1.5 | 11.2 ± 1.7 × 8.4 ± 1.3 | 10.0 ± 2.1 × 7.5 ± 1.3 | ||||
LxB range (mm) | na | Na | 8.2–10.9 × 7.3–10.6 | 7.9–16.4 × 6.0–10.5 | 6.4–13.8 × 5.6–12.8 | ||||
Growth Characteristics | |||||||||
Max temp (°C) | 34 | 30 to <35 | 30 to <35 | 35 | 35 | 32.5 | 35 | ||
Opt temp (°C) | 27.5–30 | 25 | 25 | 20–25 | 25–30 | 30 | 25 | ||
Min temp (°C) | 11 | >5<10 | >10<15 | >10<15 | >10<15 | >10<15 | 15 | ||
Lethal temp (°C) | na | >37.5 | >37.5 | na | <37.5 | ||||
Growth rate at optimum (mm/day) | ca. 7.5 (CA), ca. 8 (V8A) | ca. 4.5 (CA), ca. 7 (V8A) | 8.20 (V8A) | 9.18 (V8A) | 5.9–7.4 (CA) | 8.65 (V8A) | |||
Growth rate at 20°C (mm/day) | 5 (V8A), 3.0 (CA) | 4.5 (V8A), 3.0 (CA) | 7.75 (V8A) | 6.12 (V8A) | 3.8–5.2 (CA) | 5.96 (V8A) | |||
Colony morphology | On CA, stellate, defined edge, aerial mycelium in centre | Stellate-petaloid on V8, CA, PDA and MEA, moderately fluffy | Uniform and fluffy on MEA and V8A, stellate with limited aerial mycelium on CA and PDA | Appressed and cottony with no distinctive growth pattern and regular smooth margins on CA, V8A and PDA; sparse, slow growth on MEA | Appressed with no distinctive growth pattern and regular smooth margins on CA, V8A, MEA and PDA | Radiate to faintly radiate with very limited aerial mycelium and regular smooth margins on CA, V8A, MEA and PDA | Appressed with no distinctive growth pattern and regular smooth margins on CA, V8A and PDA, sometimes slightly petaloid on V8A; sparse on MEA |