Resistance to a highly aggressive isolate of Sclerotinia sclerotiorum in a Brassica napus diversity set

Abstract

Sclerotinia stem rot (SSR) of oilseed rape (OSR, Brassica napus), caused by Sclerotinia sclerotiorum, is a serious problem in the UK and worldwide. As fungicide-based control approaches are not always reliable, identifying host resistance is a desirable and sustainable approach to disease management. This research initially examined the aggressiveness of 18 Sclerotinia isolates (17 S. sclerotiorum, one S. subarctica) on cultivated representatives of B. rapa, B. oleracea and B. napus using a young plant test. Significant differences were observed between isolates and susceptibility of the brassica crop types, with B. rapa being the most susceptible. Sclerotinia sclerotiorum isolates from crop hosts were more aggressive than those from wild buttercup (Ranunculus acris). Sclerotinia sclerotiorum isolates P7 (pea) and DG4 (buttercup), identified as 'aggressive' and 'weakly aggressive', respectively, were used to screen 96 B. napus lines for SSR resistance in a young plant test. A subset of 20 lines was further evaluated using the same test and also in a stem inoculation test on flowering plants. A high level of SSR resistance was observed for five lines and, although there was some variability between tests, one winter OSR (line 3, Czech Republic) and one rape kale (line 83, UK) demonstrated consistent resistance. Additionally, one swede (line 69, Norway) showed an outstanding level of resistance in the stem test. Resistant lines also had fewer sclerotia forming in stems. New pre-breeding material for the production of SSR resistant OSR cultivars relevant to conditions in the UK and Europe has therefore been identified.

Resistance to Sclerotinia sclerotiorum in wild Brassica species and the importance of Sclerotinia subarctica as a Brassica pathogen

“…As line 81 is a DH line, the resistance should be genetically fixed, which should allow a more straightforward route for introgression into B. napus . In resistance screen 2, lines 14 and 81 exhibited a significantly higher level of resistance in petiole tests than B. napus line 62, a line which was previously identified as the most resistant of 96 lines from a B. napus diversity set (line 69; Taylor et al ., ). To the authors’ knowledge, this is the first report of S. sclerotiorum resistance in B. cretica , which hence provides another potential source of useful breeding material.…”

“…Using this test, only a single wild Brassica line (39, wild B. oleracea ) was significantly more resistant than the commercial B. napus cultivar Temple (line 57). Brassica napus line 59, which showed consistent resistance over the two leaf assays, also showed partial resistance in previous work using stem inoculation of mature plants (line 83; Taylor et al ., ). As observed in the petiole tests, some S. sclerotiorum resistance was also evident in B. incana lines using the leaf test, although a different line (line 17) was the most resistant.…”

“…The aim of this study was to screen wild Brassica species for resistance to S. sclerotiorum to attempt to identify new and higher level sources of resistance than those identified previously in B. napus (Taylor et al ., ). To achieve this, and overcome the problem of highly variable wild Brassica morphotypes, improved detached petiole and detached leaf assays were developed.…”

Who is sowing our seeds? A systematic review of the use of plant genetic resources in research

“…R.J. Snowdon, Bus et al 2011). UKVGB accessions have also been incorporated into a lettuce diversity set (Burns et al 2011), carrot diversity set (see Table 1), onion diversity set (see Table 1), and B. napus diversity set (Taylor et al 2015). Specific searches for publications using these research-derived resources were undertaken, and added to the group of publications identified previously.…”

First report of Sclerotinia subarctica in France detected with a rapid PCR-based test

“…A c c e p t e d M a n u s c r i p t (Holst-Jensen et al 1998;Clarkson et al 2010Clarkson et al , 2013Clarkson et al , 2017Warmington 2014) and on vegetables such as bean, cabbage, carrot, celery root, Jerusalem artichoke, lettuce, pea, potato, pumpkin, rutabaga and turnip rape (Winton et al 2006;Warmington 2014;Norskog et al 2014;Brodal et al 2016;Clarkson et al 2017). This host range is still quite modest compared to that of S. sclerotiorum (more than 400 species, Boland & Hall 1994), but it is likely to continue increasing in future years, as suggested by infectivity tests carried out with S. subarctica isolates from meadow buttercup on additional plant species such as broccoli, canola and turnip (Clarkson et al 2010;Taylor et al 2015). …”