Stable Quantitative Resistance Loci to Blackleg Disease in Canola (Brassica napus L.) Over Continents

Raman, Harsh; Raman, Rosy; Diffey, Simon; Qiu, Yu; McVittie, Brett; Barbulescu, Denise M.; Salisbury, P. A.; Marcroft, S. J.; Delourme, Régine

doi:10.3389/fpls.2018.01622

Cited by 37 publications

(63 citation statements)

References 57 publications

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“…Therefore, identification and deployment of both effective R and QR genes is needed for stable canola production. In previous studies, genetic resistance to L. maculans has been mapped in various Australian populations derived from Ag-Castle, AG-Spectrum, AV-Sapphire, Dunkeld, Maluka, Rainbow, Skipton, Shiralee and Surpass400 [3][4][5][6][8][9][10][39][40][41] . Both parental lines of the RADH population, RP04 and Ag-Outback, have shown good levels of blackleg resistance under field conditions previously.…”

Section: Discussionmentioning

confidence: 99%

Genetic and physical mapping of loci for resistance to blackleg disease in canola (Brassica napus L.)

Raman

Diffey²,

Barbulescu

et al. 2020

Sci Rep

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Sustainable canola production is essential to meet growing human demands for vegetable oil, biodiesel, and meal for stock feed markets. Blackleg, caused by the fungal pathogen, Leptosphaeria maculans is a devastating disease that can lead to significant yield loss in many canola production regions worldwide. Breakdown of race-specific resistance to L. maculans in commercial cultivars poses a constant threat to the canola industry. to identify new alleles, especially for quantitative resistance (QR), we analyzed 177 doubled haploid (DH) lines derived from an RP04/Ag-Outback cross. DH lines were evaluated for QR under field conditions in three experiments conducted at Wagga Wagga (2013, 2014) and Lake Green (2015), and under shade house conditions using the 'ascospore shower' test. DH lines were also characterized for qualitative R gene-mediated resistance via cotyledon tests with two differential single spore isolates, IBCN17 and IBCN76, under glasshouse conditions. Based on 18,851 DArTseq markers, a linkage map representing 2,019 unique marker bins was constructed and then utilized for QTL detection. Marker regression analysis identified 22 significant marker associations for resistance, allowing identification of two race-specific resistance R genes, Rlm3 and Rlm4, and 21 marker associations for QR loci. At least three SNP associations for QR were repeatedly detected on chromosomes A03, A07 and C04 across phenotyping environments. Physical mapping of markers linked with these consistent QR loci on the B. napus genome assembly revealed their localization in close proximity of the candidate genes of B. napus BnaA03g26760D (A03), BnaA07g20240D (A07) and BnaC04g02040D (C04). Annotation of these candidate genes revealed their association with protein kinase and jumonji proteins implicated in defense resistance. Both Rlm3 and Rlm4 genes identified in this DH population did not show any association with resistance loci detected under either field and/ or shade house conditions (ascospore shower) suggesting that both genes are ineffective in conferring resistance to L. maculans in Australian field conditions. Taken together, our study identified sequencebased molecular markers for dissecting R and QR loci to L. maculans in a canola DH population from the RP04/Ag-Outback cross. Blackleg, caused by the fungal pathogen Leptosphaeria maculans, is a major disease of the canola (Brassica napus L., A n A n C n C n , 2n = 4× = 38) industry especially in Australia, Canada, and France. Developing new cultivars resistant to blackleg is recognized as the most economically and environmentally safe strategy to control yield losses. Traditional breeding for blackleg resistance largely relies on the selection of elite 'good looking' lines in disease nurseries where there is high disease pressure from a diverse pathogen population. Utilizing this strategy, several canola varieties have been developed and released for commercial cultivation with ratings of moderate-to highly-resistant (to blackleg) without any prior knowledge of either r...

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Section: Discussionmentioning

confidence: 99%

Genetic and physical mapping of loci for resistance to blackleg disease in canola (Brassica napus L.)

Raman

Diffey²,

Barbulescu

et al. 2020

Sci Rep

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“…Flowering and other phenotypic data collected from different experiments were analysed using linear mixed models in R as described previously (Raman et al , 2018). Essentially we defined the individual experimental Plot as factor, with 432 levels for each of the 2015 and 2016 trials.…”

Section: Methodsmentioning

confidence: 99%

GWAS hints at pleiotropic roles forFLOWERING LOCUS Tin flowering time and yield-related traits in canola

Raman

Qiu

et al. 2019

Preprint

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Transition to flowering at the right time is critical for local adaptation and to maximize seed yield in canola, which is an important oilseed crop. There is extensive variation among canola varieties in flowering time. However, our understanding of underlying genes and their role in canola productivity is still limited. We reveal natural variation in flowering time and response to photoperiod in a diverse GWAS panel (up to 368 accessions) of canola and identify associated SNPs across multiple experiments. Complementary QTL and eQTL mapping studies were also conducted in an Australian doubled haploid (DH) population for flowering time and other grain yield related traits. We show that several associations that were repeatedly detected across experiments map in the vicinity of FLOWERING LOCUS T (FT) paralogues and its known transcriptional regulators. QTL mapping study in a DH population detected consistent genomic regions close to FT paralogs. FT sequences vary between accessions and FT expression in field and controlled environment grown plants was correlated with flowering time. FT paralogs displayed association not only with flowering time, but also with plant emergence, shoot biomass and grain yield. Our findings suggest that FT paralogs not only modulate flowering time but also modulate yield-related productivity traits in canola.HighlightThe genetic association, eQTL and expression analyses suggest that FT paralogs have multifaceted roles in canola flowering time, plant development and productivity traits.

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“…While many of the R genes have been identified [4][5][6][7][8][9], quantitative resistance (QR) is not well understood. QR can be attributed to multiple genomic regions in B. napus [10], with many of the same loci found in multiple canola cultivars [11]. QR to blackleg in canola is believed to be expressed primarily in adult plants.…”

Section: Introductionmentioning

confidence: 99%

Exploring Mechanisms of Quantitative Resistance to Leptosphaeria maculans (Blackleg) in the Cotyledons of Canola (Brassica napus) Based on Transcriptomic and Microscopic Analyses

Hubbard

Zhai

Peng

2020

Plants

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Using resistant cultivars is a common approach to managing blackleg of canola/rapeseed caused by Leptosphaeria maculans (Lm). Quantitative resistance (QR), as opposed to major-gene resistance, is of interest because it is generally more durable, due to its multi-genetic basis. However, the mechanisms and genes underlying QR are mostly unknown. In this study, potential QR modes of action in “74‑44 BL” was explored. This Canadian canola cultivar showed moderate but consistent race-nonspecific resistance at the cotyledon and adult-plant stages. A susceptible cultivar, “Westar”, was used as a control. After inoculation, the lesions developed more slowly on the cotyledons of 74-44 BL than those of Westar. We used RNA sequencing (-RNA-seq) to identify genes and their functions, putatively related to this resistance, and found that genes involved in programmed cell death (PCD), reactive oxygen species (ROS), signal transduction or intracellular endomembrane transport were most differentially expressed. ROS production was assessed in relation to Lm hyphal growth and lesion size; it occurred beyond the tissue colonized by Lm in 74-44 BL and appeared to trigger rapid cell death, limiting cotyledon colonization by Lm. In contrast, Lm grew more rapidly in Westar, often catching up with the ring of ROS and surpassing lesion boundaries. It appears that QR in 74-44 BL cotyledons is associated with limited colonization by Lm possibly mediated via ROS. The RNA-seq data also showed a link between ROS, signal transduction, and endomembrane vesicle trafficking, as well as PCD in the resistance. These results provide a starting point for a better understanding of the mechanisms behind QR against Lm in canola.

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Stable Quantitative Resistance Loci to Blackleg Disease in Canola (Brassica napus L.) Over Continents

Cited by 37 publications

References 57 publications

Genetic and physical mapping of loci for resistance to blackleg disease in canola (Brassica napus L.)

Genetic and physical mapping of loci for resistance to blackleg disease in canola (Brassica napus L.)

GWAS hints at pleiotropic roles forFLOWERING LOCUS Tin flowering time and yield-related traits in canola

Exploring Mechanisms of Quantitative Resistance to Leptosphaeria maculans (Blackleg) in the Cotyledons of Canola (Brassica napus) Based on Transcriptomic and Microscopic Analyses

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