Table 7.
Morphological characters and dimensions (mean ± SD; μm), cardinal temperatures (°C) and temperature-growth relations (mm/d) on V8-juice agar of Phytophthora species from Subclades 10b and 10c. Most discriminating characters are highlighted in bold. Percentages in brackets are ranges of isolate means; – means character not observed.
| Subclade 10b | Subclade 10c | |||||||
|---|---|---|---|---|---|---|---|---|
| P. subarctica | P. tonkinensis | P. ukrainensis | P. boehmeriae b | P. boehmeriae c | P. t. boehmeriae-liked | P. morindae | P. gondwanensis | |
| No. of isolates/source | 4a | 4a | 4a | Tucker 1931 | Chowdappa et al. 2014 | Frazzi 1950 | Nelson & Abad 2010 | 5a |
| Sporangia | 72.8 % ovoid-elongated ovoid, 7.2 % limoniform, 7.2 % ampulliform, 6.1 % obpyriform (pyrif., ellips. | 36.4% sub-globose, 35.7% broad-ovoid, 25.3% ovoid (obpyrifornì, ellipsoid) | 73.6% ovoid, 23.6% obpyriform (ellipsoid, subglobose, ampulliform) | globose, ovoid, ellipsoid, obturbinate | globose, ovoid, ellipsoid, (obturbinate, obpyriform) | globose to subglobose, ovoid | ellipsoid, obpyriform, limoniform, mouse-shaped | 59.3% ovoid to broad-ovoid, 36.7 limoniform, (subglobose, obovoid, obpyriform) |
| apex | nonpapillate | nonpapillate | nonpapillate | papillate, few bipapillate | papillate | papillate | papillate, few bipapillate | papillate, few bipapillate |
| Ixb mean | 53.8 ± 11.5 x 31.6 ± 4.1 | 29.0±3.2 x 23.7±3.1 | 35.9±4.7 x 26.2±3.4 | 51.8 x 40.1 | 35.3±4.8 x 20.5±3.4 | 42 x 34 | 42 x 21.8 | 44.7±3.9 x 28.7±2.9 |
| range of isolate means | 43.5–58.2 x 29.2-34.1 | 27.8-29.8 x 23.0-24.0 | 34.0-38.1 x 23.5-29.9 | n.a. | 32.8-38.8 x 18.2-28.6 | n.a. | n.a. | 42.9-46.0 x 27.7-30.0 |
| total range | 32.7-127.6 x 16.3-39.5 | 19.5-37.1 x 14.5-31.6 | 26.3-58.2 x 18.7-36.3 | 28-69 x 20-51 | n.a. | 18.5-53 x 11.5-46 | 30-54 x 19.2-24 | 35.7-62.2 x 21.5-35.7 |
| l/b ratio | 1.73 ± 0.46 | 1.23 ± 0.15 | 1.38 ± 0.19 | 1.29 | 1.72 (1.22-1.96) | 1.20 | 1.93 | 1.57 ± 0.16 |
| caducity | (+) | – | – | + | + | + | + | + |
| pedicels | – | – | – | <5 | 4.1 ±0.6 | 4.5 (3.5-16) | 26 (8-66) | 3.5 ± 1.3 |
| internal proliferation | nested and extended | nested and extended | nested and extended | – | – | – | – | – |
| exitpores | 10.4 ± 1.7 | 9.8 ± 1.7 | 8.4 ± 1.5 | n.a. | n.a. | n.a. | n.a. | 3.3 ± 0.5 |
| sympodia | rare, lax | – | – | frequent | n.a. | loose, up to 16 sporangia | dense, umbellate | dense, 3-5 sporangia |
| zoospore cysts | 10.6 ± 0.9 | 10.4 ± 1.0 | 10.4 ±1.1 | n.a. | n.a. | 11.5-14 | n.a. | 9.5 ± 0.7 |
| Breeding system Oogonia | sterile | homothallic golden-brown with age | sterile | homothallic globose to subglobose | homothallic | homothallic | homothallic | homothallic |
| mean diam | – | 46.2 ± 6.2 | – | 26.5 | 22.5 ± 3.9 | 31.5 | 30.4 | 28.1 ± 3.0 |
| range of isolate means | – | 45.1-48.4 | – | 20.9-31.7 | 21.9-25.1 | n.a. | n.a. | 27.2-28.9 |
| total range | – | 30.3-59.1 | – | n.a. | n.a. | 19-38 | 21.6-39.6 | 14.1-33.0 |
| tapering base | – | 11% (0-22%) | – | n.a. | n.a. | occurring | frequent | 13.3% (10-16%) |
| comma-shaped | – | 23% (12-40%) | – | n.a. | n.a. | n.a. | n.a. | 31.3% (24-38%) |
| elongated/excentric | – | – | n.a. | n.a. | n.a. | – | 22.7% (20-26%) | |
| Oospores | – | |||||||
| plerotic oospores | – | 69% (56-84%) | – | predominantly | predominantly | predominantly | 100% | 75.3% (70-80%) |
| mean diam | – | 42.9 ± 5.5 | – | 23.3 | n.a. | 27.5 | 30.3 | 23.9 ± 2.6 |
| Total range | – | 28.4-56.9 | – | 15.7-27.6 | n.a. | 16-34 | 21-38.9 | 11.6-28.7 |
| wall diam | – | 1.6 ± 0.3 | – | <2 | n.a. | n.a. | 3.2 (2.4-3.6) | 2.0 ± 0.34 |
| oospore wall index | – | 0.24 ± 0.03 | – | n.a. | n.a. | n.a. | n.a. | 0.42 ± 0.04 |
| Abortion rate | – | 6.3% (4-8%) | – | n.a. | n.a. | n.a. | n.a. | 44.7% (24-66%) |
| Antheridia | – | 98% paragynous | – | 100% amphigynous | 100% amphigynous | 100% amphigynous | 100% amphigynous | 100% amphigynous |
| size | – | 14.1±2.2 x 10.8±2.0 | – | 12-16 x 11-15 | 12.4±2.1 x 10.0±1.3 | 16.5x14.5 (12.5-21 x 8-16) | 11.2 x 8.5 | 12.4±2.1 x 10.0±1.3 |
| Chlamydospores | – | – | – | rare; thickwalled (2pm) | + (27 out of 43 isolates) | + | – | – |
| size | – | – | – | 41.4 (16-51) | - | 29.5 (17-42) | – | – |
| Hyphal swellings | limoniform, rare | coralloid, irregular hyphae | ovoid, limoniform; 9.1 ± 1.5; coralloid hyphae | – | – | – | – | – |
| Hyphal aggregations | – | + | + | n.a. | n.a. | n.a. | n.a. | – |
| Maximum temperature | >30-<32.5 | >20-<25 | >32.5-<35 (30-32.5) | 32.5 | <35 | <35 | 27 | >30-<32.5 |
| Optimum temperature | 25 | 20 | 32.5 (30) | 25 | n.a | n.a. | 20 | 27.5 |
| Growth rate at 20 °C | 1.21 ± 0.14 | 1.13 ± 0.1 | 1.48 ± 0.21 | 4.4 | n.a. | n.a. | 2.9 | 3.17 ±0.3 |
| Growth rate at 25 °C | 1.31 ± 0.16 | 0 | 2.15 ± 0.12 | 6.6 | 7.6 ± 0.06 | n.a. | n.a. | 5.05 ± 0.21 |
a Numbers of isolates included in the growth tests: P. subarctica = 4; P. tonkinensis = 5; R ukrainensis = 4; P. gondwanensis = 5.
b Morphological studies and temperature-growth test performed on cornmeal agar.
c Morphological studies performed on CA; temperature-growth test performed on CA and only at 24 and 35 °C.
d Morphological studies performed on PDA; temperature-growth test performed on PDA.