Table 1.
The latitude and longitude for field experiment sites and the associated weather stations over three growing seasons (2010/11, 2011/12 and 2012/13).
Table 2.
Oilseed rape (Brassica napus) cultivars/lines and Leptosphaeria maculans isolates used in the controlled environment experiments to confirm the presence of Rlm genes or quantitative resistant (QR).
Fig 1.
Phoma stem canker symptoms on plants from a winter oilseed rape field experiment.
Stems of cultivar Adriana (A) (Rlm4+QR) with resistance gene Rlm4 and quantitative resistance (QR) had less severe stem canker than cultivar Bilbao (B) (only Rlm4); similarly those of cultivar DK Cabernet (C) (Rlm1+QR) had less severe stem canker than cultivar Capitol (D) (Rlm1). Stems were sampled from the field experiment at Morley, Norfolk on 8 July 2013.
Table 3.
Comparison of phoma stem canker severity and seed yield between different oilseed rape cultivars grown in winter oilseed rape field experiments at 13 sites over three growing seasons (2010/2011, 2011/2012, 2012/2013).
Fig 2.
Distribution of relative phoma stem canker severity.
The distribution of relative phoma stem canker severity for each cultivar from winter oilseed rape field experiments at 13 sites in three growing seasons (2010/11, 2011/12 and 2012/13). Each box-plot shows the mean (broken line) and median (solid line) percentage relative phoma stem canker severity. The lower and upper boundaries of the boxes indicate relative phoma stem canker severity for the 25th and 75th percentiles, while whisker bars below and above each box indicate relative phoma stem canker severity for the 5th and 95th percentiles. The black dots below and above each box-plot represent the minimum and maximum relative phoma stem canker severities, respectively.
Fig 3.
Relationships between cultivar phoma stem canker severity (SCi) and site mean phoma stem canker severity (SSj).
The relationships between SCi and SSj in winter oilseed rape field experiments at 13 sites in three growing seasons (2010/11, 2011/12 and 2012/13). Analysis of position and parallelism showed five distinct groups, with three groups in Fig 3A: Drakkar (broken short line, SC = 2.53+0.96SS), Capitol and Bilbao (broken long line, SC = 0.22+1.14SS), NK Grandia (solid line, SC = 0.14+0.88SS) and with two groups in Fig 3B: Adriana and DK Cabernet (broken long-short line, SC = -0.50+1.05SS), Ex-Astrid, Roxet and Excel (dash-dot line, SC = -0.70+0.92SS).
Table 4.
The simple correlation coefficients calculated between stem canker score at harvest and the mean temperature (°C) or the total rainfall (mm) over three growing seasons (2010/2011, 2011/2012, 2012/2013) at 13 sites.
Fig 4.
Distribution of relative seed yield.
The distribution of relative seed yield for each cultivar from field experiments at 13 sites in three growing seasons (2010/11, 2011/12 and 2012/13). Each box-plot shows the mean (broken line) and median (solid line) relative seed yield. The lower and upper boundaries of the boxes indicate relative seed yield for the 25th and 75th percentiles, while whisker bars below and above each box indicate relative seed yield for the 5th and 95th percentiles. The black dots below and above each box-plot represent the minimum and maximum seed yields, respectively.
Fig 5.
Relationship between individual cultivar seed yield (YCi) and site mean seed yield (YSj).
The relationship between YCi and YSj in winter oilseed rape field experiments at 13 sites in three growing seasons (2010/11, 2011/12 and 2012/13). Analysis of position and parallelism showed five distinct groups, with three groups in Fig 5A: Excel (broken short line, YC = 0.03+1.18YS), NK Grandia and Adriana (solid line, YC = -0.01+1.11YS), Drakkar (dash-dot line, YC = -0.39 + 0.58YS) and with two groups in Fig 5B: Ex-Astrid, DK Cabernet and Bilbao (broken long line, YC = 0.40+1.02YS), Roxet and Capitol (broken long-short line, YC = -0.29+0.99YS).
Fig 6.
Relationship between relative cultivar seed yield (RY, %) and relative cultivar phoma stem canker severity (RS, %).
The relationship was fitted (broken short line) by the logistic equation () using the data from winter oilseed rape field experiments at 13 sites (see Table 1) in three growing seasons (2010/2011, 2011/2012, 2012/2013).
Table 5.
Characteristics of the race structure of Leptosphaeria maculans populations at different experimental sites in the UK, France and Germany.
Fig 7.
Phoma stem canker severity in controlled environment experiment.
Cultivar difference in the severity of phoma stem canker scored on a 0–6 scale (A) and the internal length of phoma stem canker symptoms (B) that had developed at 20°C by 49 days after inoculation of leaf petioles of different cultivars/lines with conidial suspensions of Leptosphaeria maculans isolates. For details of isolates, see Table 2. Error bars are standard errors of the difference. Multiple comparisons were done using the least significance difference at significance level P≤0.05. The values for phoma stem canker severity or the internal length of phoma stem canker symptoms that had different letters differed significantly at P≤0.05.
Fig 8.
Phoma stem canker symptoms that developed in a controlled environment experiment.
External (A, B, C) and internal (D, E, F) phoma stem canker symptoms on DH line A30 (A, D), cultivars Bilbao (B, E) and Adriana (C, F). A30 with no known Rlm resistance genes and no quantitative resistance (QR), Bilbao (Rlm4) with resistance gene Rlm4, Adriana (Rlm4 + QR) with Rlm4 and QR. Leaf petioles were inoculated with conidia of Leptosphaeria maculans isolate v23.11.9, which is virulent against Rlm4. Inoculated plants were kept at 20°C with 12h light/12h darkness and sampled at 49 days after inoculation.