The necrotrophic fungus, Sclerotinia sclerotiorum, employs an array of cell wall-degrading enzymes (CWDEs), including cellulase, to dismantle host cell walls. However, the molecular mechanisms through which S. sclerotiorum degrades cellulose remain elusive. Here, we unveil a novel secretory cellobiohydrolase, SsdchA, characterized by a signal peptide and a Glyco_hydro_7 (GH7) domain. SsdchA exhibits a robust expression of during early infection stages. Interestingly, colony morphology and growth rates remain unaffected across the wild-type, SsdchA deletion strains and SsdchA overexpression strains on potato dextrose agar (PDA) medium. Nevertheless, the pathogenicity and cellobiohydrolase activity decreased in the SsdchA deletion strains, but enhanced in the SsdchA overexpression strains. Moreover, the heterologous expression of SsdchA in Arabidopsis thaliana leads to reduced cellulose content and heightened susceptibility to S. sclerotiorum. Collectively, our data underscore the pivotal role of the novel cellobiohydrolase SsdchA in the pathogenicity of S. sclerotiorum.

Seed weight is a component of seed yield in rapeseed (Brassica napus L.). Although quantitative trait loci (QTL) for seed weight have been reported in rapeseed, only a few causal quantitative trait genes (QTGs) have been identified, resulting in a limitation in understanding of seed weight regulation. We constructed a gene coexpression network at the early seed developmental stage using transcripts of 20,408 genes in QTL intervals and 1017 rapeseed homologs of known genes from other species. Among the 10 modules in this gene coexpression network, modules 1 and 2 were core modules and contained genes involved in source–flow–sink processes such as synthesis and transportation of fatty acid and protein, and photosynthesis. A hub gene SERINE CARBOXYPEPTIDASE-LIKE 19 (SCPL19) was identified by candidate gene association analysis in rapeseed and functionally investigated using Arabidopsis T-DNA mutant and overexpression lines. Our study demonstrates the power of gene coexpression analysis to prioritize candidate genes from large candidate QTG sets and enhances the understanding of molecular mechanism for seed weight at the early developmental stage in rapeseed.

Seed number per silique (SNPS) is one of seed yield components in rapeseed, but its genetic mechanism remains elusive. Here a double haploid (DH) population derived from a hybrid between female 6Q006 with 35–40 SNPS and male 6W26 with 10–15 SNPS was investigated for SNPS in the year 2017, 2018, 2019 and 2021, and genotyped with Brassica 60K Illumina Infinium SNP array. An overlapping major QTL (qSNPS.C09) explaining 51.50% of phenotypic variance on average was narrowed to a 0.90 Mb region from 44.87 Mb to 45.77 Mb on chromosome C09 by BSA-seq. Subsequently, two DEGs in this interval were detected between extreme individuals in DH and F₂ populations by transcriptome sequencing at 7 and 14 days after pollination siliques. Of which, BnaC09g45400D encoded an adenine phosphoribosyltransferase 5 (APT5) has a 48-bp InDel variation in the promoter of two parents. Candidate gene association analysis showed that this InDel variation was associated with SNPS in a nature population of rapeseed, where 54 accessions carrying the same haplotype as parent 6Q006 had higher SNPS than 103 accessions carrying the same haplotype as parent 6W26. Collectively, the findings are helpful for rapeseed molecular breeding of SNPS, and provide new insight into the genetic and molecular mechanism of SNPS in rapeseed.

A narrow genetic base has hindered improvement of Brassica juncea (A^jA^jB^jB^j). In this study, large-scale genomic components were introduced from diploid ancestor species into modern B. juncea using a digenomic hexaploid strategy. The hexaploids A^jA^jA^rA^rB^jB^j and A^jA^jB^jB^jBⁿBⁿ were first developed from B. juncea × B. rapa (A^rA^r) and B. juncea × B. nigra (BⁿBⁿ), and then crossed with dozens of B. nigra and B. rapa, respectively. Both types of hexaploid showed high pollen fertility and moderate seed set throughout the S₁ to S₃ generations, and could be crossed with diploid progenitor species under field conditions, in particular for the combination of A^jA^jB^jB^jBⁿBⁿ × B. rapa. Thirty A^jA^rB^j-type and 31 A^jBⁿB^j-type B. juncea resources were generated, of which the A^jA^rBⁿB^j type showed higher fertility. Of these new-type B. juncea resources, 97 individual plants were genotyped with 42 simple sequence repeat markers, together with 16 current B. juncea accessions and 30 hexaploid plants. Based on 180 polymorphic loci, the new-type B. juncea resources and current B. juncea were separated clearly into distinct groups, with large genetic distance between the new-type B. juncea resources and current B. juncea. Our study provides a novel approach to introducing large-scale genomic components from diploid ancestor species into B. juncea.