Table 4.
Aggressiveness indices (Ag) of Colletotrichum gloeosporioides populations from six D. alata yam fields tested on four yam cultivars: Kabusah, Pacala, Tahiti and Plimbite (the cultivar of reference for the susceptibility to anthracnose).
| N | Aggressiveness (Ag-index) estimated on four |
D.alata | cultivars | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Levels | cv Kabusah | cv Pacala | cv Tahiti | cv Plimbite (ref) | ||||||||
| host cv Kabusah | 17 | 47.8 | (7.5) | a | 71.1 | (6) | b | 16.6 | (5.2) | b | 51.6 | (7.2) a |
| host cv Pacala | 13 | 36.4 | (9) | ab | 91.5 | (7.1) | a | 11.7 | (6.1) | b | 56.6 | (8.6) a |
| host cv Tahiti | 15 | 20.3 | (8.3) | b | 69.3 | (6.4) | b | 44.7 | (5.5) | a | 54 | (7.7) a |
| KabA – field | 8 | 41.4 | (5.5) | ab | 59.9 | (8.2) | ab | 12.1 | (7.5) | b | 43.4 | (10.4) a |
| KabB – field | 9 | 53.4 | (6.3) | a | 81.1 | (7.7) | ab | 20.7 | (7) | b | 59 | (9.8) a |
| Pacc – field | 7 | 48 | (5.9) | a | 90 | (8.2) | a | 13.5 | (7.5) | b | 65.9 | (10.4) a |
| PacD – field | 6 | 13.3 | (5.7) | b | 94.5 | (11.6) | a | 8 | (10.5) | b | 38 | (14.7) a |
| TahA – field | 9 | 25.8 | (10.8) | ab | 58.8 | (7.7) | b | 37.1 | (7) | a | 59.7 | (9.8) a |
| TahB – field | 6 | 13 | (12.4) | b | 85 | (9.5) | ab | 56.2 | (8.6) | a | 45.5 | (12) a |
| Genetic cluster 1 | 13 | 23.3 | (9.3) | a | 66.2 | (6.9) | a | 43.4 | (6.3) | a | 53.3 | (8.3) a |
| Genetic cluster 2 | 15 | 42.4 | (5.2) | a | 73.2 | (6.5) | ab | 17.5 | (5.9) | b | 54 | (7.7) a |
| Genetic cluster 3 | 16 | 38.6 | (6.1) | a | 86.8 | (6.3 | a | 16.8 | (5.7) | b | 54 | (7.5) a |
| prob F, effect = host cultivar | 0.061 | 0.048∗ | 0.000∗∗∗ | 0.908 | ||||||||
| prob F, effect = field of origin | 0.075 | 0.019∗ | 0.002∗∗∗ | 0.472 | ||||||||
| prob F, effect = genetic group (cluster) | 0.294 | 0.088 | 0.005∗∗∗ | 0.998 | ||||||||
Fields KabA/TahA, and KabB/TahB were contiguous (see Figure 1). a, b stands for the groups of significant differences of aggressiveness tested using Student’s t-test with a p-value p < 0.01. Tests were performed considering separately each of the four inoculated cultivars and each of the fungal population grouping levels, host cv, field and genetic cluster. ∗,∗∗∗, respectively, indicates significant values with p-values below 0.05 and 0.001. Standard errors are specified in brackets.