Figure 1:
Relative abundance (proportion of total field PPN population) for each sampled field in the Spring of 2022 or 2023. Each column represents one sampled field and the total community of PPNs found in that field. Fields are organized by grass species and colored by the proportion of each PPN genus detected in the field. A column with no color (i.e., white) had undetectable populations of PPN. * indicates a field with fewer than four individual nematodes for the total population count.
Figure 2:
Comparative PPN relative abundance (proportion of total field PPN population) in annual ryegrass and orchardgrass seed fields sampled in spring (top) and autumn (bottom) 2022. Each column represents one sampled field at either time point. Fields are organized by grass species and colored by the proportion of each PPN genus detected in a field. A column with no color (i.e., white) had undetectable populations of PPN. * indicates a field with fewer than four individual nematodes for the total population count.
Table 1:
Average plant-parasitic nematode species densities and diversity measures for all grass species sampled in 2022 and 2023.
| Grass species | Nb | Sample time | Average Density (#/100 g soil) | Diversity Measuresa | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Pratylenchus | Meloidogyne | Helicotylenchus | Paratylenchus | Tylenchorhynchus | Xiphinema | Alpha | Beta | Gamma | |||
| Annual ryegrass | 14 | Spring 2022 | 90 | 206 | 0 | 1 | 0 | 0 | 1.9 | 0.6 | 3 |
| Autumn 2022 | 0 | 34 | 0 | 0 | 0 | 0 | 0.7 | 0.4 | 1 | ||
| Bentgrass | 3 | Spring 2023 | 169 | 38 | 0 | 0 | 0 | 0 | 1.7 | 0.2 | 2 |
| Fine fescue | 3 | Spring 2023 | 3 | 0 | 0 | 0 | 0 | 0 | 1.0 | 0.0 | 1 |
| Orchardgrass | 7 | Spring 2022 | 227 | 58 | 22 | 14 | 1 | 0 | 2.1 | 1.4 | 5 |
| Autumn 2022 | 0 | 20 | 7 | 0 | 0 | 1 | 1.1 | 1.7 | 3 | ||
| Perennial ryegrass | 5 | Spring 2023 | 3 | 6 | 1 | 1 | 0 | 0 | 2.0 | 1.0 | 4 |
| Tall fescue | 5 | Spring 2023 | 166 | 4 | 0 | 0 | 0 | 1 | 1.6 | 0.9 | 3 |
a Diversity measures calculated as described by Whittaker (1972). Alpha diversity is expressed as the average number of plant-parasitic nematode species per grass species, or species richness; beta diversity is expressed as the ratio of gamma diversity over alpha diversity minus 1, or heterogeneity; gamma diversity is expressed as the total estimated number of plant-parasitic nematode species per grass species, or the landscape level diversity.
Table 2:
Percentage frequency of occurrence (%FO), mean population densities when present (# nematodes/100 g soil), and maximum population densities (# nematodes/100 g soil) of plant-parasitic nematodes associated with grass for seed crops in Oregon sampled in Spring 2022 or 2023.
| Pratylenchus | Meloidogyne | Helicotylenchus | Paratylenchus | Tylenchorhynchus | Xiphinema | |
|---|---|---|---|---|---|---|
| %FOa | 97 | 54 | 16 | 8 | 3 | 3 |
| Meanb | 117 (30.2) | 172 (61.7) | 26 (18.2) | 32 (26.4) | 7 | 1 |
| Maxc | 1,984 | 2,496 | 288 | 556 | 24 | 2 |
a Percent frequency of occurrence during the spring timepoint of sampling, calculated as the number of fields with detections of a particular nematode species.
b Mean population density for a given nematode species during the spring collection time point based on average population density in fields with detectable populations (i.e., fields with zero counts were not included in the calculation of the mean). Standard errors of the means are presented in parentheses. For those with no value in parentheses, only one sample had a detection of the individual nematode, and thus a standard error could not be calculated.
Table 3:
Pratylenchus spp. identified on grass for seed crops in Oregon.a
| Grass type | P. crenatus | P. fallax | P. neglectus | P. penetrans | P. thornei |
|---|---|---|---|---|---|
| Annual ryegrass | + (11)b | + (2) | + (9) | + (5) | −c |
| Perennial ryegrass | ndd | nd | nd | nd | nd |
| Bentgrass | + (3) | − | − | − | − |
| Tall fescue | + (1) | − | − | − | − |
| Fine fescue | nd | nd | nd | nd | nd |
| Orchardgrass | + (1) | − | + (6) | + (2) | + (2) |
a Species was determined by amplifying COX1 mitochondrial region with the primer set JB3/JB4.5 followed by sequencing.
b + indicates a positive PCR and sequencing result for a Pratylenchus spp. The number of fields from which the species was identified is indicated in parentheses.