Chawade, A. | Search bioRxiv

bioRxiv2024

Genomic loci for sclerotinia stem rot resistance and chlorophyll stability in Brassica napus: integrating GWAS with microbiome insights

Sclerotinia Stem Rot (SSR) disease is one of the most serious diseases affecting the yield and quality of oilseed rape (Brassica napus). Understanding the genetic basis of the resistance trait in oilseed rape to SSR and microbiome composition for enhanced resistance is crucial for developing resistant varieties and sustainably mitigate the impact of the disease. In this study, in a panel of 168 oilseed rape accessions, most resistant (NGB 13503 and NGB 13834) and susceptible (NGB 13497 and NGB 13897) accessions are identified. A Genome-wide association study (GWAS) identified 47 SNPs linked to the SSR lesion length, lesion area, and lesion relative to the leaf area. Among the SNPs significantly linked to lesion length were Bn-A04-p10555408, Bn-A07-p12487549, Bn-A09-p4652268, Bn-A09-p4916858 and to our knowledge, these SNPs have not been previously linked to SSR resistance in oilseed rape. Moreover, the study identified 24 SNPs linked with chlorophyll content before SSR inoculation (SPADH), after the SSR inoculation (SPADI), and chlorophyll index (CI). Maintaining the chlorophyll level is correlated with the SSR resistance. Furthermore, bacterial taxa (e.g. Pseudomonas, Methylobacterium, and Aquabacterium) and fungal taxa (e.g. Mycosphaerellales, Thelebolales, and Akanthomyces) were enriched in the resistant compared to in the susceptible oilseed rape accessions. The SNPs linked to lesion length showed consistent haplotype variation between these selected accessions. Given the absence of complete resistance against SSR, the study provides insights into the significance of maintaining chlorophyll levels and considering microbiome composition for enhancing the level of existing partial resistance to SSR in oilseed rape.

plant biology↗

bioRxiv2024

Plant genotype-specific modulation of Clonostachys rosea-mediated biocontrol of septoria tritici blotch disease on wheat

BackgroundBeneficial microorganisms can act as biological control agents (BCAs) by directly targeting pathogens or indirectly by enhancing the plants defense mechanisms against pathogens. However, efficiencies with which plants benefit from BCAs vary, potentially because of genetic variation in plants for plant-BCA compatibility. The aim of this study was to explore the genetic variation in winter wheat for modulation of Clonostachys rosea-mediated biocontrol of septoria tritici blotch disease caused by the fungal pathogen Zymoseptoria tritici. ResultsIn total, 202 winter wheat genotypes, including landraces and old cultivars grown from 1900 onwards in the Scandinavian countries, were tested under greenhouse-controlled conditions. Foliar spray applications of the pathogen and the fungal BCA in two treatments, i.e., Z. tritici (Zt) alone and Z. tritici along with C. rosea (ZtCr) were used to assess the disease progress over time. The absence and presence of C. rosea in Zt and ZtCr, respectively, allowed the dissection of variation for plant disease resistance and biocontrol efficacy. The study showed significant phenotypic variation among plant genotypes for disease progression in both Zt and ZtCr treatments. Moreover, disease progress for individual plant genotypes differed significantly between the two treatments, indicating a plant genotype-dependent variation in biocontrol efficacy. For the phenotypic variation in disease progress and biocontrol efficacy, a genome-wide association study using a 20K single-nucleotide polymorphism (SNP) marker array was also performed. In total, five distinct SNP markers associated with disease resistance and four SNP markers associated with C. rosea biocontrol efficacy were identified. ConclusionsThis work serves as a foundation to further characterize the genetic basis of plant-BCA interactions, facilitating opportunities for concurrent breeding for disease resistance and biocontrol efficacy.

plant biology↗