Bee communities in canola are affected by landscape context and farm management

Bees are key pollinators that promote greater yield and seed quality of oilseed crops such as canola. Canola acreage has increased over 1,000% in the past decade in the Pacific Northwest USA, providing a major pulse of sugar-rich nectar and pollen resources that may affect bee health and community structure. However, because canola does not require insect pollination for seed production, few studies have examined the biodiversity of pollinators taking advantage of these resources, or the floral traits of canola that affect pollinators across variable landscapes. Here, we conducted pollinator surveys at canola farms across the inland Northwest region of the USA. We surveyed bee biodiversity and abundance, and assessed how these metrics correlated with landscape context, canola production practices, and floral traits of various canola varieties. We found that bee communities differed between sites and across growing seasons, with sweat bees more abundant later in the season, and mining bees more abundant earlier in the season. We also found that bees were more abundant overall on farms with less floral nectar and with less developed landscape surrounding the sampling area. Bee diversity was greater in spring canola than winter canola, and floral traits were also correlated with differing bee community diversity. This research provides important information for canola growers and land managers and offers a framework for future research in pollinator management in the inland Northwest.

Clubroot resistance derived from the European Brassica napus cv. ‘Tosca’ is not effective against virulent Plasmodiophora brassicae isolates from Alberta, Canada

In this study, clubroot resistance in the resynthesized European winter Brassica napus cv. ‘Tosca’ was introgressed into a Canadian spring canola line ‘11SR0099’, which was then crossed with the clubroot susceptible spring line ‘12DH0001’ to produce F1 seeds. The F1 plants were used to develop a doubled haploid (DH) mapping population. The parents and the DH lines were screened against ‘old’ pathotypes 2F, 3H, 5I, 6M and 8N of the clubroot pathogen, Plasmodiophora brassicae, as well as against the ‘new’ pathotypes 5X, 5L, 2B, 3A, 3D, 5G, 8E, 5C, 8J, 5K, 3O and 8P. Genotyping was conducted using a Brassica 15K SNP array. The clubroot screening showed that ‘Tosca, ‘11SR0099’ and the resistant DH lines were resistant to three (2F, 3H and 5I) of the five ‘old’ pathotypes and four (2B, 3O, 8E and 8P) of the 12 ‘new’ pathotypes, while being moderately resistant to the ‘old’ pathotype 8N and the ‘new’ pathotypes 3D and 5G. ‘Tosca’ was susceptible to isolates representing pathotype 3A (the most common among the ‘new’ pathotypes) as well as pathotypes 6M, 5X, 5L, 5K and 8J. Linkage analysis and QTL mapping identified a ca. 0.88–0.95 Mb genomic region on the A03 chromosome of ‘Tosca’ as conferring resistance to pathotypes 2F, 3H, 5I, 2B, 3D, 5G, 8E, 3O and 8P. The identified QTL genomic region housed the CRk, Crr3 and CRd gene(s). However, the susceptibility of ‘Tosca’ to most of the common virulent pathotypes makes it unattractive as a sole CR donor in the breeding of commercial canola varieties in western Canada.

Identification of lncRNAs in response to infection by Plasmodiophora brassicae in Brassica napus and development of lncRNA-based SSR markers

Clubroot resistance in spring canola has been introgressed from different Brassica sources; however, molecular mechanism underlying this resistance, especially the involvement of long non-coding RNAs (lncRNAs), yet to be understood. We identified 464 differentially expressed (DE) lncRNAs from the roots of clubroot resistant canola, carrying resistance on chromosome BnaA03, and susceptible canola lines challenged with Plasmodiophora brassicae pathotype 3. Pathway enrichment analysis showed that most of the target genes regulated by these DE lncRNAs belonged to plant-pathogen interaction and hormone signaling, as well as primary and secondary metabolic pathways. Comparative analysis of these lncRNAs with the previously reported 530 DE lncRNAs, identified using resistance located on BnaA08, detected 12 lncRNAs which showed a similar trend of upregulation in both types of resistant lines; these lncRNAs probably play a fundamental role in clubroot resistance. We identified SSR markers within 196 DE lncRNAs. Genotyping of two DH populations carrying resistance on BnaA03 identified a marker capable of detecting the resistance in 98% of the DH lines. To our knowledge, this is the first report of the identification of SSRs within the lncRNAs responsive to P. brassicae infection demonstrating the potential use of the lncRNAs in the breeding of Brassica crops.

From Dimness to Glossiness—Characteristics of the Spring Rapeseed Mutant Form without Glaucous Bloom (Brassica napus L.)

As a result of the treatment of “Vikros” spring canola with the chemical mutagen ethyl methanesulfonate (EMS), a high-protein mutant form without glaucous bloom (wax bloom) on leaves, shoots, and siliques was isolated. Segregation into glossy and glaucous forms was always observed in the progeny of glossy plants from self-pollination, and the proportion of glaucous plants could reach up to 25%. The progeny of glaucous plants were homogeneous and did not segregate. If during the period of seed germination and seedling development the soil did not dry out and remained moist, and the average daily temperature did not exceed 16 °C, then the amount of glossy plants could reach 99%. Glossy plants possessed qualities valuable for breeding forage varieties, such as the increased content of protein in seeds (more than 30%), and change phenol metabolism, чтo прoявляется a reduced amount of lignin and sinapine in comparison with the original cultivar. In addition, plants without wax coating showed weakened shoot growth, decreased pollen fertility and seed production, and reduced lignin content in the shoots. Glossy mutants are of interest for the obtaining of fodder low-sinapine and low-lignin varieties of spring rapeseed.

A Leptosphaeria maculans set of isolates characterised on all available differentials and used as control to identify virulence frequencies in a current French population

The characterization of virulence frequencies has to be regularly updated to identify which genes are currently efficient and use this information to advise gene deployment by choosing varieties depending on the current composition of local pathogen population. In L. maculans on Brassica napus, because different genes were characterized by different teams, because new interactions are continuously identified and seed of differentials are difficult to obtain, we today still lack isolates characterized on all current resistance genes. On the one hand, we assembled a set of 12 isolates characterized on 13 of the 17 described resistance genes, having clearly compatible and clearly incompatible isolates for each interaction. This set can be used to characterize the L. maculans – B. napus interaction at cotyledon stage. Expanding the set of isolates with clearly virulent ones allowed us to detect inconsistent behaviour or intermediate (avirulent) phenotypes. On the other hand, we used this set of isolates as controls to identify virulence frequencies in a current French L. maculans population sampled in 2018 at Le Rheu. We provide the current status for 13 avirulence frequencies, including LepR1, LepR2 and LepR3 available in near isogenic lines of spring canola but not yet documented in France. Avirulence frequencies on the genes Rlm1, Rlm2, Rlm3, Rlm4, Rlm7, Rlm9 and LepR3 were low, indicating the lack of efficacy of these genes against the current population. In the opposite, all or most of isolates were avirulent for the genes Rlm5, Rlm6, Rlm10, Rlm11, LepR1 and LepR2. An optimistic point of view could conclude that there are ample resources for oilseed rape breeding. However, as compared to previous studies, so far all the resistance genes used on significant acreage without additional management practices have lost efficacy and only avirulences corresponding to resistance genes not deployed in France retain efficacy. While the call to wisely manage the available host resistance genes is not recent, it is still relevant. Adding, management practices to the deployment of resistance genes in order to reduce inoculum carry-over from one growing season to the next and to lower population sizes is key to maintain their efficacy over time.